I installed some aftermarket VDO gauges in my aux pod. The oil psi and volt gauges are working fine. However, I would like to now install the oil & volt warning lights. I already purchased the lil lights that I am going to use but need some help w/ the wiring. I looked in the Haynes manual (page 288) but can not figure out how to wire in the "warning lights"...
I "think" the brown wire is used for the charge indicator light but have no idea how to wire in the oil light...
This is a good question. I've checked my '86 and '88 service manuals for the wiring schematics for both lights and there's nothing to be found. However, for the charge light circuit, I remember seeing a schematic in a post a while back that was about an alternator failing to charge because of the light bulb being burned out. A number of people questioned why that would affect anything, but the important thing is that someone posted the wiring schematic of the voltmeter gauge with the integral circuit for the light. You might try a search for charging problems, but I'm afraid you'll end up with a million threads to go through. I'll keep looking.
As for the oil pressure light, it can't be too hard to figure out. If I'm not mistaken, there are three wires leading out of the oil presseure sender. The tan one is for the gauge, and one of the other two provides the ground to the oil pressure light. Take an ohmmeter and test which of the two pins starts off at zero ohms with the engine stopped, and goes to infinite ohms once the engine is started. That will be the wire you want to use to trigger the light. You can double check it by pulling the back of the instrument pod off and following the leads on the printed circuit that lead from the light to the instrument panel connector. One of them will probably lead to connector C2 pin 9 which is a pink/black power wire, and the other should lead to the same color wire you tested earlier in the engine bay.
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09:10 PM
Cajun Member
Posts: 1562 From: Youngsville, La., USA Registered: Dec 2003
I searched but could not location any information on a warning light for the "oil pressure". There are warning lights for the charging system and coolant. The only place I currently know of to get that information would be from the oil pressure switch. The same switch that provides the secondary power path for the fuel pump. This switch would give you a "low" pressure signal. I'm not sure of what the pressure setting is of the switch.
A note, if you elect to down that this path I would suggest you use an isolation relay in the circuit.
You can double check it by pulling the back of the instrument pod off and following the leads on the printed circuit that lead from the light to the instrument panel connector. One of them will probably lead to connector C2 pin 9 which is a pink/black power wire, and the other should lead to the same color wire you tested earlier in the engine bay.
I have the stock aux. gauges to trace the leads back to the connector location. However, I no longer have the chassis connector that plugs into the aux. gauges! All I have are the 5 wires from the chassie harness the the connector cut off and MIA...
Someone wouldent happen to have the pin out for the chassis Aux gauge connector? Also a diragram of its position into the back of the aux. gauges?
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09:55 PM
Fieroking Member
Posts: 2144 From: Coeur D Alene Idaho USA Registered: Jun 2002
The reason you can't find the wire for the Oil Pressure light is that there isn't one. The low oil pressure light function in built into the gauge! The only wire from the Oil Pressure sender is the Tan wire.
Joe Sokol
------------------ 85 SE Daily driver with a 3.4 DOHC OBD II 88 Formula/GT 4.9 Allante Intake (My Baby)
I can photograph mine and post it tomorrow if nobody beats me to it, 'cos there's nothing in the SM. But now that Cajun mentioned it, I checked my own wiring schematic for my SBC TPI conversion and I wired my oil pressure light to one of the pins on the oil pressure switch for the fuel pump relay bypass circuit. I can't remember off hand though whether the switch was an original Fiero or Camaro part. Interestingly, the oil switch for the fuel pump relay bypass system in the Fiero SM shows that pins A and C are used, but shows nothing for what pin B does, or if there even is one. Might be a good place to start looking.
Fieroking is probably right on this one. But that doesn't mean you can't do as I did with my TPI. I'll do a bit of research in my records and see if I can't come up with a part number for the pressure switch I used since it has the dual fuel relay bypass and idiot light switch circuits on it.
Fieroking is probably right on this one. But that doesn't mean you can't do as I did with my TPI. I'll do a bit of research in my records and see if I can't come up with a part number for the pressure switch I used since it has the dual fuel relay bypass and idiot light switch circuits on it.
Thanks Blooz! Don't go to crazy figuring this out, as my VDO oil PSI gauge is working fine. Just thought it would be nice to have a light go on to catch my attention if things went south...
If your up to it, I have a more pressing issue with my "Ajar" dash light staying on That issue can be viewed at the below link:
I've got some more info for you there ALJR... in my '88, there's a separate pigtail with connectors at both ends that connects the gauges pod to the rest of the car wire harness. The end that plugs into the car harness is called connector C211 and looks like first photo below. The other end of that pigtail plugs into the gauge pod and looks like the second photo (a little unfocused, but hey I never said I was a photographer ) Here's what the wire colors are and what they're used for:
C211 pin A pnk/blk goes to pod connector 2 - used for 12V C211 pin B tan goes to pod conn 3 - oil pressure signal C211 pin C not used C211 pin D brown goes to pod conn pin 1 - not used for V6 but spliced to circuit used for charge light on 4 cyl C211 pin E not used C211 pin F grey goes to pod conn pin 5 - used for general pod lighting C211 pin G not used C211 pin H black goes to pod conn pin 4 - used for ground
So then, you could probably look for a way to use the signal from the brown wire on C211 pin D to run your charge indicator light, but you'd want to check how that plays out at the alternator end of things given the CS alternator on the '88's.
As for the oil pressure light, I've figured out that the three wires at the stock sender won't help you out at all. The stock orn/blk wire is 12V, the tan/wht wire is the continuation of the orn/blk wire once the oil pressure is above 4 psi (so the switch is open when there's no pressure which is opposite to what you want) and finally the tan wire is for the pressure gauge signal.
So I checked out my SBC TPI layout since I did the same as you with aftermarket gauges and lights, and found that I used two different senders: one is a dedicated one-wire oil pressure sender for the gauge, and the other sender is a two pole switch. The two pole switch is from the stock Camaro TPI (VIN F) from '87-on. One pole works like the fuel pump bypass feature on the Fiero sender, and the other switches the remaining pin to ground when the oil pressure is under 4 PSI. So I used this pin to trip my oil pressure light. To install both senders, I threaded a tee into the oil pressure port on the engine. You wouldn't need to buy both senders though since you would leave the Fiero oil pressure sender in bone stock configuration including the fuel pump bypass circuit, then tee-in the Camaro switch with a brass plumbing fitting, and hook up the ground wire for your oil light to pin D of the new switch. I've got the illustrated parts manual for the '87 Camaro here so I'll look up the part number for you if you decide to go this route.
Thanks for all that Blooz! I am going to tackle that project once I figure out why my dam Ajar light is staying on...
Wonder if it would be esier to take apart the factory aux. gauge and isolate the circuit used for the light... Or maybe not... I do have some extra wires back there from my auto to 5spd swap and I am also planning on wiring up mu oil temp gauge as well. Sounds like a good project to do at the same time Rather then T'ing off the existing fuel pressure line, I could install one of those sandwich plates between the oil filter (which I would need for the oil temp) and put two sensors on there...
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01:02 PM
PFF
System Bot
Msaby Member
Posts: 292 From: Allentown, PA 18104 Registered: Sep 2001
I am just starting to look at wiring up my VDO guages now. My thoughts were to use 2 oil pressure switches and run separate circuits one for the guage and one for the light. Or you can purchase a sender from VDO which permits the use of a light and a guage.
Hey Blooz is the stock TPI sender the same ohms that the vdo oil gauge requires?
Thanks Mike
[This message has been edited by Msaby (edited 01-17-2010).]
Mike: My VDO oil pressure gauge used the stock GM oil pressure sender (90 ohms full scale deflection of needle)
ALJR: Another option for oil temp is to go with a VDO sender that replaces your oil pan drain plug. It's pretty slick and it's what I've been using for 15 years on my TPI. Have a look:
I just purchased the sandwich adapter plate off ebay for $29 shipped... I am going to also purchase the VDO temp sender for my oil gauge. I will also purchase the oil PSI sender when I find a suitable unit...
Blooz, do you know the "warrning" psi level for the sender your using? Also, do you know if they make a stand alone "warning" sender; one that does not have the gauge function?
The oil sender I seen has a warning level of 7psi, which seems kind of low...
The Camaro one I mentioned in my earlier post is a simple switch without the gauge sender. It's just that it also has two switches in one: the fuel relay bypass switch and the low oil pressure switch. The pressure that the light comes on at is 4 PSI on that one... kinda low too, but it's what was avail at the time.
Ahhh ok.. That is too low... I found a warning-light only sending unit at summit racing... On below 18psi; they have others of different psi thresholds... Any idea what a good psi level would be? I am thinking the 18 psi will do...
Originally posted by Fieroking: The reason you can't find the wire for the Oil Pressure light is that there isn't one. The low oil pressure light function in built into the gauge! The only wire from the Oil Pressure sender is the Tan wire.
Yes... No engine switch for a light. This a function of the gage. I don't know how the gage work. I think the gage has a switch that turn on when low pressure.
If light is separate, you can add switch to engine. It a pretty standard part...
12-15 psi low light, I think, the engine switch is configure for. 18 is fine.
quote
the oil pressure should be 20-60 psi.
Source: 87 owner manual
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
The reason you can't find the wire for the Oil Pressure light is that there isn't one. The low oil pressure light function in built into the gauge!
This is the correct answer. There is a two-transistor comparator/driver circuit that controls the light. Here is a schematic that was previously posted somewhere (perhaps on PFF, I don't know the source), but I haven't yet verified for myself whether it's accurate or not:
If this is your original work or you can identify the source, please let me know and I will update my post to give proper credit.
Also note that the CS130 alternator in the '88 Fieros does not use the 'Charge' indicator lamp to energize the alternator field. Rather, the regulator switches the 'L' terminal (on the alternator) to ground whenever an undervoltage or overvoltage condition is detected. My '88 FSM does indeed identify that as a brown wire from the 'L' terminal on the alternator to pin 1 on the "rally gauge panel."
[This message has been edited by Marvin McInnis (edited 01-19-2010).]
i have some cheapie VDO oil and batt gauges now, i would like to have an idiot like for both of these. right now i have a alternator charge indicator circuit to show that it is working. since i have hte newer alternator that requires a 5v signal to start charging, i had to build a circuit for that. first one burnt up and i didnt know till i couldnt start the car.
i would like to know the circuit that needs to be built to show these. maybe i could build one for my fuel pressure gauge when its installed. goes off the same idea, pressure. ------------------ First LX9 Fiero GT, 1987 | My Fiero Fuel Economy | MPG Display for OBD I Youtube Videos of My GT | modernize your fiero with technology! If you can't fix it with a hammer, you've got an electrical problem Fiero's are people too. We pay just as much attention to them, if not more than our loved ones screw paying those bastards. im not going to become rich by paying for things.....
[This message has been edited by americasfuture2k (edited 01-20-2010).]
