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HELP -1988 GT V8 Swap - Oil Pressure, Water Temperature, and Gas Gauges Not Working by V8Steve
Started on: 12-28-2019 09:02 PM
Replies: 48 (1616 views)
Last post by: V8Steve on 06-05-2020 09:15 AM
V8Steve
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Report this Post12-28-2019 09:02 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm on the last steps of the resurrection of this car but really need some help with the gauges.

First, the history:

The V8 swap was done in 1999 with a ZZ4, TPI, and Painless harness. After roughly 4 years, I swapped the car over to a center mounted throttle body and BigStuff3 injection. The wiring mess was not visible to the casual observer but I continued to drive the car until the ZZ4 failed in 2007. During that time and 26,000 miles, despite the wiring mess, all the gauges worked. The gas gauge tank float was probably original. From 2007 until 2015 the car sat in my shop with a cracked block.

In summer 2015, I removed the ZZ4 and began the rebuild. Inside the engine bay were remnants of the OEM harness, remnants of the Painless TPI harness, wires too long, wires too short, burned wires, etc. I decided to clean up the entire engine bay and clean up the wiring. Before engine removal, every wire was labeled. The cleanup involved removing the C500 connector as well as the old power and ground posts. When I eliminated the C500 connector, I probed every wire going in and checked continuity to the mating wire leaving the connector. One by one, I cut and spliced them. The connectors were all marine grade with a heat sensitive adhesive.

The car is now running with a new 355 cubic inch motor and Holley multi-port injection.

Back to the gauges:
It seems odd that all three would fail and I suspect there is a common cause to this problem and it may not be that all three of them have failed.

Fuel Gauge - The fuel float sender is new and I'm aware that there are sometimes problems with these getting stuck inside the tank.

Oil Gauge - The oil sending unit is new. Right now it's not connected because I put in a mechanical gage for the dyno testing. When I turn on the key, the needle peaks to the right.

Water Temperature - Today I studied the 88 GM Manual and checked the ohms on the sensor. I couldn't get consistent readings to match the GM Manual but I noticed the ohms dropping while it warmed up in my hand. A new sensor is on the way. Meanwhile, I checked resistance on the female plug to ground and found both of them were grounded. That seems not right but my strong point is not in the electrical side.

I'm hoping someone might lead me toward a common cause that impacts all three gauges. Actually, I'd welcome any help with this last nagging problem.

------------------
88GT 355 CI Sequential Holley Multiport , AFR milled 180, Dyno'd at 427 HP, 320 WHP
anderson@gdsconsulting.com

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Report this Post12-28-2019 11:30 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did you check the GAGE fuse?

Have you had the instrument cluster out of the car?

The water temp circuit is routed through the C500, but the oil pressure circuit goes through C203 and the fuel gage circuit doesnt pass through either connector.
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Report this Post12-29-2019 12:09 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks. I'll find and check that fuse tomorrow.

You make good points. The oil pressure tan wire should not be rocket science. The fuel sender should not have been impacted at all.

Instrument cluster - No, it was never removed since 1999 when I made a change to accommodate the V8 tach signal. The cluster is almost ready to come out now. I'm talking about the large cluster in front of the steering wheel. I've had the little one out lately ----> the one with oil pressure and voltage. BTW, the voltage charging gauge works fine.

[This message has been edited by V8Steve (edited 12-29-2019).]

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Report this Post12-29-2019 08:07 AM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have had the same problem since converting my 87 3.4 to the 88 style pressure sending unit. As soon as I turn on the ignition, it blows the gauge fuse. With the fuse blown the gauge stays pegged to the bottom of the gauge. Disconnect the harness, the fuse doesn't blow and the gauge still stays pegged.
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Report this Post12-29-2019 08:45 AM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

I have had the same problem since converting my 87 3.4 to the 88 style pressure sending unit. As soon as I turn on the ignition, it blows the gauge fuse. With the fuse blown the gauge stays pegged to the bottom of the gauge. Disconnect the harness, the fuse doesn't blow and the gauge still stays pegged.


It sounds like you dont have the new plug wired properly.
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Report this Post12-29-2019 11:15 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
I checked the fuse for the gauges and it's OK. The GM factory manual for the 88 shows all the routing so I think the next step is make sure all the wires go to the right places. The simplest is the single wire from the oil pressure gage so I'll trace it from the sensor through the console (which is still apart) right up to center mounted gage pod above the radio. The sensor is new and I'll double check the resistance. I had also checked the old one and it was OK. The ohms changed when run up against my air compressor nozzle.

The car is almost ready to drive after the resurrection began in June 2015, going on 5 years now but I don't want to drive it without monitoring oil pressure and water temperature on this new motor. A laptop connected to the Holley ECU tells me the coolant temperature and the fan goes on and off per the programmed setpoints.
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Report this Post12-29-2019 11:58 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post

V8Steve

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Here's the schematic. Can anyone tell me what the numbers mean like the 3 and .35 and 31 next to TAN?

I know this gauge set is getting power because the alternator charging voltage gauge right next to it is working.

[This message has been edited by V8Steve (edited 12-29-2019).]

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Report this Post12-29-2019 02:13 PM Click Here to See the Profile for FieroJimmySend a Private Message to FieroJimmyEdit/Delete MessageReply w/QuoteDirect Link to This Post
3 is the pin number in the Aux gauge pod connector. 31 is the circuit number. .35 is the metric wire size (0.35mm).

I didn't see if anyone else mentioned it yet, but if you don't have the sender for the oil pressure plugged in the gauge will peg high.
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Report this Post12-29-2019 03:24 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
FieroJimmy - Thanks. Right now the sensor is in the box. Solving the EFI starting problem with the old Bigstuff3 was such a huge problem all efforts went into just getting it running. I was so concerned about the oil pressure as related to the image below, changing hose lengths, etc. that I put a regular mechanical gage right on the motor with copper tubing. We made certain there was always oil pressure. There was a lot at stake. In the image below you can see the "A" engraved on both housings.

Now that it's running with good oil pressure, I can spend time on the dash gage.

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Report this Post12-29-2019 04:53 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post

V8Steve

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I ran a test for the oil pressure gauge.

First I turned on the key with the sensor disconnected. The pointer pinned right away to the right and the little oil can light was out.

Then I plugged in the connector to the sensor and made sure the housing was grounded. When I turned the key, the needle stayed at the low end and bumped a bit when key was turned. ALSO, the red oil can light went on.

So this tells me the front of the car is communicating with the sensor at the back of the car.

I've been talking about the TAN wire because that's what the manual shows. But look at the plug...it only has a bluish green and the tan had been cut off. Since my 1st V8 swap was almost 20 years ago, I can't remember why it ended up this way. Even so, it still worked OK for years.

Here's the plug:

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Report this Post12-29-2019 05:44 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
The correct plug will have three wires.
The two outside wires (C & D, farthest apart) are for the oil pump pressure switch that backs up the relay, the center wire (A)is the resistance circuit for the gage.
(A) is the wire closest to the clip on the plug.
Are you using a three pin sending unit for Oil Pressure?

[This message has been edited by olejoedad (edited 12-29-2019).]

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Report this Post12-29-2019 06:17 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Both the old and the new sending units are identical three wire units. From Day 1 of the 1999 swap I'm certain we used only the center wire. The two side wires are orange and tan but both are snipped off. The 1st generation had a Painless harness with own relay that started the fuel pump. Same thing with Bigstuff3 injection after that. The new Holley also turns on the fuel pump with own relay.

The factory manual for the 1988 shows only one wire from the sending unit and that's what I have and it's from the center.

Will put it back into the motor and try tomorrow.

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Report this Post12-29-2019 07:18 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
That is the correct location for the gage signal.

The other two wires acted as a backup power circuit for the fuel pump, in case the relay failed.
The circuit is in the ECU wiring section of the FSM.
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Report this Post01-03-2020 01:26 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Oil pressure now working! I removed the gauge pod and separated the plug underneath. Then I checked the ohms from the sending unit plug all the way to the first plug and finally through the second plug under the pod. All was OK. I started the car and gauge works perfectly. I don't know why it didn't work before but at least I know now there is continuity from the sender plug all the way to the pod and it works.

Now, on to the water temperature and gas gage plus problems with the serpentine walking off the tensioner pully (different thread).
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Report this Post01-03-2020 03:07 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Cool! On to the water temp then.....

What temperature sending unit are you using?
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Report this Post01-03-2020 11:31 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
ACDelco 213-928. It's exactly like the one I took out.

Next step is to trace all the wires from the sender plug up to the cluster. Meanwhile, the serpentine tensioner belt walking must be solved so that I can run the motor long enough to produce temperature.
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Report this Post01-04-2020 07:15 AM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
That sensor will not run the gage, it is the sensor that communicates with the PCM.
It can be replaced with the 3 wire sensor from certain GM models (sorry, dont have P/N right now).

Your tensioner pulley axis of rotation is not parallel with the rest of the pulleys, either from improper mounting, bad bearings or a worn out tensioner assembly.
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Report this Post01-04-2020 09:07 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
The water temperature sensor has always been a two wire sensor and the new one is identical to the old one. I believe the old one still works. More work to do on my end.

I agree 100% on the belt problem and pulley alignment. See other thread, page 2 : Serpentine

I borrowed the Gates laser tool again and rechecked all the pulleys one more time. They all checked out but there's still a walking problem. I think the new tensioner meets parallel and angularity requirements when unloaded but is deflecting out of position when loaded with the belt. Will check again with laser, loaded and unloaded on Tuesday when I borrow the tool again. Meanwhile, I swapped the tensioner pulley to a smooth non-ribbed Dayco. It seems to have higher flanges and it has a crown in the middle. This is going to take more time as well as shimming the pulley in/out as well as possibly shimming/tilting the tensioner itself. Dayco tells me it's OK to run the ribbed belt on a smooth tensioner pulley.

[This message has been edited by V8Steve (edited 01-04-2020).]

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Report this Post01-04-2020 10:23 AM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Are you using stock Fiero gages?

The sensor you linked to is hooked up to the PCM via a yellow wire and a black wire.
It does not work with the stock Fiero temperature gage.

To run the gage and the PCM, use AC Delco P/N 12551708.
It is a three pin sensor - two wires to communicate with the PCM and 1 wire to run the gage.
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Report this Post01-04-2020 11:06 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Gages are stock Fiero. Ever since the 1st V8 swap in 1999 the car has always run with two temperature sensors, one for the ECU and another for the gage, both with just two wires.

I plan to connect the tach next to see if it still works. The white wire simply plugs into the MSD 6+ box. Since the tach, temperature, and fuel are all in the main cluster I might learn more since both the temperature and fuel gages don't work. If the tach doesn't work it might point to a problem within the cluster itself.
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Report this Post01-04-2020 11:52 AM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Tach and fuel are on connector C3 (vertical 18 pin connector on right side of dash cluster), and water temp is on connector C2 (horizontal 12 pin connector on left side of cluster).

The contact fingers on the flex circuit board sometimes (many times) come loose from the substrate and short to their neighbors.

The sensor you linked earlier is for the ECU (PCM), and typically uses a 5v signal.
I do not know for sure if the sensor has the capability of operating with 12v, and am unsure if the resistance values are the same as the stock Fiero sensor.
If it does meet the above criteria, the black wire on the plug would need to be grounded to the block to complete the resistance circuit to drive the gage.

The stock Fiero temp gage sensor is also two pin, but two separate circuits - a resistance circuit for the gage and a switch circuit for the HOT lamp. The sensor grounds through the threads, and uses a rectangular plug with part of two sides on the sensor missing. There is also a sensor with a similar plug to the sensor you referenced that is sold as a replacement for the stock Fiero gage/light sensor.
One way you can determine if the sensor you have for the gage is correct is to check for resistance between the sensor threads and one of the pins on the sensor.
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Report this Post01-11-2020 02:06 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Good break in weather today so I worked on the tach and fuel gage.

Tach - The white tach wire had always worked so it was a simple matter to remove the MSD Plus 6 box to gain access to the tach signal. I plugged in the tach wire and it all worked so I set the RPM cutoff limit, tidied up the wire and put everything back.

Fuel Gage - Following the FSM service manual I disconnected the plug under the car and then turned the key on. The FSM says if it goes to FULL, repair or replace the sender. Well, it went right up to FULL and stayed there after I turned off the key. Next I disconnected the battery and reconnected the fuel connector under the car. Then I removed the entire cluster from the dash.

If the above test with key on goes to full, the FSM says the sender is the problem and to check the pink wire for high resistance on #7 of the C3 pinout test. It should normally be 0 ohms for empty and 90 ohms for full. I got around 15 ohms and I know the tank is pretty low. The gage cluster is on the bench and the fuel needle has gone to around 5/8. Before that, it wanted to stay on FULL. I'm not sure why it didn't just return to zero. Something doesn't add up because it says one symptom of a bad sender is high resistance but mine was in the normal range.

I'm not quite sure what to do next. I'm inclined to add a few gallons of gas to the tank to see if the pink wire resistance increases. On the other hand, if I'm looking at removing the tank, it's a lot easier when nearly empty. The sending unit, pump, and float are all new.

Below are photos of the plug under the car as well as the gage stuck on 5/8 while siting on the bench. One of the plug wires is cutoff and bypasses the plug. With my V8 swap, that wire powers the fuel pump and is controlled by the Holley multiport ECU. That cut off wire has been that way since the first V8 generation of this car in 1999.

[img][/img]

[This message has been edited by V8Steve (edited 01-11-2020).]

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Report this Post01-11-2020 03:22 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
If the gage has a 15Ω load, the gage should respond, provided it has power and ground. From your SM test, full gage travel indicates this.

In reviewing your thread, I didnt see where the fuel gage problem was described, other than 'not working'.
Could you provide more info?

And if it is something with the gage, Forum member JGunsett repairs and recalibrates OEM Fiero gages. You can reach him via PM.
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Report this Post01-11-2020 03:50 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
This was my first pass at the fuel gage. It always worked before and during my V8 swap right up until the ZZ4 quit. Once I got the car running last month I noticed the water temp and the fuel gage were both not working. The fuel gage was always on EMPTY and the temperature gage was always pinned to the left. For the time being, together with the warm weather, today was a good day to get under the car and check out the fuel gage issues.

Unless someone points me in a better direction, I plan to check the pink wire ohms again, add fuel, and check again.

[This message has been edited by V8Steve (edited 01-11-2020).]

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Report this Post01-11-2020 05:03 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
That is a good plan.

Check the contacts on the laminate, they are a know problem for causing crossed circuits.

I cant remember how many I have fixed.
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Report this Post01-12-2020 11:50 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Today I checked the ohms again on the pink wire and got different readings, in fact it seemed to wander. A poor ground was responsible so I connected the meter right to the battery ground and checked again. The reading was 2 ohms and stayed that way. Next I put around 2 gallons of gas in the car with no change in the ohms, even when I rocked the car a bit. No change in the 2 ohms.

Next I checked the resistance from the pink wire on the cluster plug to the same wire under the car where the 3- connector is located. The resistance was near zero so I know I have connectivity from that plug all the way to the dash cluster. Next I checked to see if there was any resistance across the ground and pink on the other end of the plug coming from the tank sending unit. I could not get the meter to record anything across those pins on the tank side. I put a probe in the ground with the other probe grounded on the block and go connectivity. The meter was on the 200 ohm beeping scale.

So this causes me ask why is there no resistance across the sender itself? The tank is roughly 1/4- 1/2 full but no reading of any kind across the plug. It's a brand new Fiero store sender that went in the tank at least two years ago. The car sat with no power until recently.
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Report this Post01-12-2020 12:00 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Time to drop the tank and take a peek inside.
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Report this Post01-12-2020 12:44 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
I agree. The warm weather is leaving and winter is coming back. Next, I'll go back to the water temperature gauge and go through the same process of tracing wires. Hopefully I can solve that one and then return to the gas gauge and remove the tank. I've done this several times and it sounds worse than it really is. Since the fill and vent hoses are all new, coupled with new underside tank clamps, it should go fast.

While the car is up on the air on jack stands and 8X8 pieces of timber framing, it's a good time to remove the alternator and tend to the walking serpentine. That problem has been traced to a tensioner that is plumb and true before you put the belt on. Once it winds up the clock spring inside to load the belt, the tension arm and pully go out of alignment. I bought a LSX manual tensioner to replace it.
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Report this Post01-12-2020 01:15 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Its good to have a plan.

[This message has been edited by olejoedad (edited 01-12-2020).]

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Report this Post01-12-2020 02:48 PM Click Here to See the Profile for FFIEROFREDSend a Private Message to FFIEROFREDEdit/Delete MessageReply w/QuoteDirect Link to This Post
On my sbc swap I have all aftermarket gages. For years I was having problems with the temp gage, and getting the FiTech TB to ground. Turns out the powder coated intake was not grounding. I had SS washers under the intake bolts to protect the PC. I had to run a ground wire to the gage sender and to one to the TB stud.
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Report this Post01-12-2020 04:14 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Fred,
Nice ride. Thanks for your input. You are right about powder coated components. I checked the sensor housing ground to the manifold and then to the block and then to the chassis. All OK. We've got "00" size cables running from the up front battery to the starter and to the block. From the block there's another short "00" size ground cable to the chassis. These heavy cables were all used to minimize starting voltage drops during cranking.
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Report this Post01-15-2020 10:41 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Back on water temperature - I'd bought a new connector pigtail to reach the sensor back when I rewired the engine bay and eliminated the C500.. The OEM wires are light green and dark green but I recall not paying any attention as to how they should be connected to the two black ones on the new connector. I found an online repair site that noted they are different and if they're reversed the gage will stay on cold. So, next chance I get I'll change them and see what happens.
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olejoedad
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Report this Post01-15-2020 01:10 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Use your meter and check which pin has resistance to the sensor shell.
That is the pin that controls the gage.

The pin that shows no continuity to the sensor shell is the pin for the switch that controls the HOT lamp.
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Report this Post01-15-2020 04:33 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
The FSM shows Pin #11 is a direct line to sensor pin for controlling the gage. The cluster is on the bench so it seems a simple matter to check the continuity all the way from Pin #11 on the C2 Pinout to the sensor pin. By doing this I should be able to 1st verify continuity and 2nd to verify the correct sensor pin. I should be able to do this with the cluster on the bench and battery disconnected. Am I right?

[This message has been edited by V8Steve (edited 01-15-2020).]

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olejoedad
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Report this Post01-15-2020 05:23 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yup
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V8Steve
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Report this Post01-15-2020 10:02 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Water Temperature Progress - I checked the new sensor and could not get any reading from any pin to the shell. It was 35F in the shop so I brought it in the house and immersed it in 140F water. Same result with no reading from any pin to the shell. Then I took a reading across the two pins in the 140F water and got 800 ohms. I'm using an AC Delco 213-928 and now I think it's the wrong one and that this one is meant for the computer. It was always a two wire sensor but I think this one is temperature only and not meant for gauge and switch. The Holley ECU is connected to what appears to be the same sensor and a laptop shows coolant temp as it should.

Before I can troubleshoot the wires and test them, I have to have the right sending unit.

Does anyone know the correct two wire sending unit PN? Is it ACDelco 213-69?

[This message has been edited by V8Steve (edited 01-15-2020).]

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Report this Post01-16-2020 01:45 PM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
Temperature Gage - I traced both wires from the cluster back to the engine bay and there is continuity on each one. The temperature sending sensor and new pigtail are not easy to find so I ordered both from the Fiero store. I'll check the unit with a meter upon arrival. I think I'm now all set as long as the correct part arrives. Before ordering it, we had a phone conversation to be certain it's the correct one with mating pigtail. Since one of the green wires passed through the S500 connector and I'd eliminated the entire connector, I'm happy that there are no new problems.

The engine bay wiring was a real mess with duplicate wires, wires going nowhere, wires too short, wires too long, etc. So far, everything is OK and I've not found any mistakes. I'd gladly share my experience to anyone attempting this. There are PFF threads showing the same and I followed those as well.

It's too cold to take out the fuel tank now so the next step is check out this temperature gage, run the car, etc. If all goes OK, now that the tach and oil pressure gage are also working, it will be time to reassemble the cluster and the entire center console. Inside the console is a Dakota Digital module to adjust the VSS for the F40 swap. Right now, that's the least of my concerns.
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Report this Post01-16-2020 01:52 PM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
Good progress.
Congratulations!
A lot of confusion has been caused by parts store computers calling out the wrong sensor for the water temp gage/hot lamp.
You are not the first to encounter this, and I'm sure not the last!
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Report this Post01-18-2020 08:37 AM Click Here to See the Profile for V8SteveClick Here to visit V8Steve's HomePageSend a Private Message to V8SteveEdit/Delete MessageReply w/QuoteDirect Link to This Post
The correct water temperature gauge/light sensor along with the matching pigtail all arrived from the Fiero Store. The sensor checks out correctly with the meter. Once this cold weather warms up the project will continue.

Before the instrument cluster goes back in, I'll check it at night to make sure all the bulbs and everything else works while I have it out.

The progress with the temperature gage has given me confidence in reading the FSM and troubleshooting. Next steps will include checking out all the lights, flashers, etc. to be sure everything works. The car has rebuilt calipers all around and a stainless brake line kit. The hand brake cables are new but I have to adjust the levers in order to get it working. It's another learning process.
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Report this Post01-18-2020 09:41 AM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
From the factory, the Fiero temp gage circuit was wired incorrectly, causing the temp gage to peg when the key is turned to the ON position.
The easy way to fix this is to pull the contact with two small gage light green wires from the ignition switch on top of the steering column. Be sure to insulate the exposed metal on the contact after pulling it to prevent unintentional grounding of the contact, it will cause the gage to peg.
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