Early V6 oil pressure sender to 1988 style conversion (Page 2/4)
fierofool JUN 09, 01:24 PM
At the time I did my 86 as shown in my thread, I didn't want to work outside for a period of time trying to splice and solder the wires, so I made the temporary connections. It's actually still working well at this time. When I did my 87, it was more suitable weather and the new terminal was hardwired in with solder and heat shrink tubing. With the fuses blowing, I questioned my work and went back to verify correct wiring.

Prior to making my trip to Carlisle GM Nationals Fiero Show and then all the way to Millinocket, Me. at the end of this month, I have ordered a replacement ACDelco sending unit to see how it holds up.
Skybax JUN 09, 07:55 PM
Installed my Made in Mexico Delco sender this afternoon, used butt connectors with heat shrink, back filled the new connector with dielectric grease, covered the wires and top of new sender with GM split wire loom. Everything looks good and no more dancing needle, hopefully I don't experience any of the weirdness mentioned above.

Have to admit I was a little hesitant to do this mod to my mostly stock car, especially with hearing history of problems above, but ultimately decided to go forward with it because it seemed the better of the only 2 options. I didn't want to install a new aftermarket old-style sender due to poor connector and prone to leaking. Have to give my original sender credit, it lasted 36 years and still doesn't leak, it was the dancing needle and crappy connector that I was tired of.

[This message has been edited by Skybax (edited 06-09-2021).]

fierogt28 JUN 10, 05:41 PM

quote
Originally posted by Raydar:


There was a run of mis-wired 88-style oil pressure switches a few (more than ten) years back. I would suspect that they have all worked their way through the system, by now.
(There was no question. Plugging them in usually caused the fuse to blow, IIRC.)

About 5 years ago, I also installed one that seemed to stick, and kept the fuel pump turned on, even with the key/engine off.
I got tired of such silliness, and switched my fuel pump to a switched circuit. Some people would say that this is ill-advised, but it has caused me exactly zero issues. But then I'm not running a high capacity pump, either.




I remember 15 years ago Ed Parks from The Fiero Factory mentioned this, but I recall it was for 85-87V6 oil pressure senders. Not 88.
If so, do you remember what brand?

Thanks for bringing it up again.

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

Skybax JUN 11, 10:29 PM
Question: If the new type sender fails/sticks/malfunctions during an outing...

is it best to just disconnect it (losing oil psi gauge and fuel pump relay backup system temporarily to get home) ?

or does it have to be plugged in to run, and if that is the case would you put a jumper between pins C and D ?
Skybax JUN 13, 12:37 PM
Welp, I have bad news...

We took the Fiero to first cruise/show yesterday and halfway there I discovered I had no dash lights.

(Side Note A: Yes it is wired correctly according to info provided on Orge's site and in forum archives)
(Side Note B: This car is in excellent original condition throughout and dash lights worked prior to this mod)

Here are the preliminary diagnostic findings...

1. No dash lights at all (including aux pod)
2. Radio clock is brightly illuminated with parking/dash lights off (normal)
3. Radio clock is completely out with parking/dash lights turned on (not normal, should be half illuminated)
4. Everything else works
5. All fuses are good
6. With everything off I have power to both sides of these fuses (#11 horn/int lights, #3 parking lights, #2 oil psi sender/fuel pump)
7. If I disconnect NEG side of batt and put test light between NEG batt and NEG batt terminal, I get dim light that fades out within 5 sec
8. Pulling one fuse at a time, if I disconnect NEG side of batt and put test light between NEG batt and NEG batt terminal, I still get dim light that fades out within 5 sec
9. Doesn't matter if the 1988 style oil sender is connected or not, all diagnostics give same results

I was hesitant in doing this mod and should have left it alone. My instinct tells me it wasn't defective switches 10 years ago, but maybe an incompatibility with this mod that causes collateral damage and yet to be discovered based on others having similar symptoms/malfunctions.

Disclaimer: I don't want to sound like a whiny "woe as me" victim but what really sucks about this is, I busted my butt on this car non-stop for the last 6 weeks (about 200 hours) in addition to my normal job to get it ready so the wife and I could enjoy some shows with friends this summer. Long story short, got into Fiero's about 20 years ago when wife and I first moved in together and we had lots of good times those years, then got into other cars/biking. Fast forward to 2013 where I had 4 separate major traumas in a 9 month period that totaled me. Most people don't come back from that, trust me I know, because western medicine is very limited and had me down the wrong path. It took me 5 freaking years and 5000 hours of study to find the truth and recover, and I did it without any meds or alcohol, so the only reason I'm able to type this message and do these things with a 99% recovery is because of God and my Wife combined with raw courage/faith/determination. So the whole point of buying a Fiero this Spring was so the wife and I could reminisce 2000-2005 and celebrate our victory on backside of 2020 nonsense. This was our first weekend out and wasn't able to go to the big car event today because I'm not comfortable taking it on a road trip with electrical malfunction due to this mod.

I'm deflated right now and don't know where to start, any help from electrical guru's would be appreciated...

[This message has been edited by Skybax (edited 06-13-2021).]

Blacktree JUN 13, 02:02 PM
The oil pressure sensor is not part of the illumination circuit. So it can't affect the dash lights. The issue with the dash lights is just coincidental.

The dash lights run off the INST fuse. I know you said the fuses are all good, but check that one again.
Skybax JUN 13, 02:10 PM
Thanks for reply, I will double check the fuse...

As a previous auto tech many years ago I agree that "coincidental stuff" can lead you down the wrong path pulling your hair out, however for others to have similar coincidental issues is often not coincidental, even when it shouldn't/doesn't make sense on paper (same as other things in life).

Can you please tell me if power to both sides of fuse #2 (oil psi sender/fuel pump) with key off is normal or not normal so I can rule out normal operation?

Also, why is there a low volt test light that fades out within 5 seconds doing a parasitic draw test?
And why does it come back / can be repeated over and over if you wait 15 seconds to retest?
It acts like residual bleed of small amount of energy, shouldn't normal be no light at all?

[This message has been edited by Skybax (edited 06-13-2021).]

Skybax JUN 13, 03:53 PM
Just double checked the instrument panel lights fuse...

- It checks good but don't have power on either terminal on the fuse box when the parking lights are turned on.

Also, I pulled the headlight & dimmer switch off the dash and checked terminals on the backside of dimmer switch...

- With parking lights off I have no power to any of the 4 wires (brown, black, white, green)

- With parking lights on I have power on the brown wire and the green wire (green wire dims with dimmer)

[This message has been edited by Skybax (edited 06-13-2021).]

Blacktree JUN 13, 05:28 PM
OK, now we're getting somewhere. Sounds like the dimmer transistor is bad.

The dimmer switch doesn't directly control the lights. It sends a signal to a transistor. The transistor uses that signal to determine how much power to send to the dash lights. That green wire you mentioned (should be dark green with white stripe) goes to the dimmer transistor. Also, the transistor powers the INST fuse.

So if you have power going through the dimmer switch, but the INST fuse has no power, then something's up with the transistor. That transistor is mounted under the dash, beside the steering column. It has an aluminum heatsink. See photo in link below.

http://rodneydickman.com/pr....php?products_id=513

There should be 3 wires attached to the transistor. The brown wire is power from the headlight switch. The dark green with white stripe is signal from the dimmer switch. The dark green wire is power to the dash lights. You can test the circuit by jumping the brown wire to the green wire. That will bypass the transistor and send power to the dash lights (if the parking lights are on). If the dash lights come on when you bypass the transistor, then the transistor is dead. You can buy the one in the link above for a reasonable price.

Best of luck!
fierofool JUN 13, 06:08 PM
I installed my new ACDelco sending unit. Doesn't blow the fuse any more. Gauge still stays pegged to the far right bottom as if it doesn't have a ground.

Does anyone have a known good used sending unit they're willing to sell?

[This message has been edited by fierofool (edited 06-13-2021).]