Wiring on '88 V6 oil switch (Page 1/1)
robmox MAY 20, 11:07 AM
I'm hoping to wire my oil switch directly to an oil pressure gauge, to hopefully diagnose if there's an electrical problem in the harness. I checked my Haynes manual, and the wiring diagram doesn't show which wire is which. But, the wiring diagram did show that the switch is wired directly to the gauge, so it's not an issue with anything in between. Does anyone have a diagram that shows which post (or which wire) is the signal? The wires are all black on my unit, so use "top left" "top right" "bottom" for the triangle positioning if you can.

I've never wired a gauge, but it's only 2 wire. Because the wires are black and white, I'm assuming positive and neutral for the gauge, and that it'll ground to the chassis?

If you have any other advice, I'd appreciate it. Thanks!
olejoedad MAY 20, 01:02 PM
Do you know the response curve of the new gge?
The Fiero works off of a 0 - 90 Ω range.

The wire by the plug catch is the signal.
robmox MAY 20, 03:30 PM

quote
Originally posted by olejoedad:

Do you know the response curve of the new gge?
The Fiero works off of a 0 - 90 Ω range.

The wire by the plug catch is the signal.



So if I hook up my multimeter, I should get 90 ohms for supply, 0 ohms for ground, and something in between for oil pressure signal?
Raydar MAY 20, 03:33 PM
One of the wires will be 12V battery. Always hot.
The other wire will be 12V switched. Hot when there's oil pressure - ANY oil pressure. (That wire feeds the fuel pump.)
The third wire will supply a varying voltage to the gauge, depending upon how much oil pressure there is.

I don't have the pinout in front of me, however.
robmox MAY 20, 04:00 PM

quote
Originally posted by Raydar:

One of the wires will be 12V battery. Always hot.
The other wire will be 12V switched. Hot when there's oil pressure - ANY oil pressure. (That wire feeds the fuel pump.)
The third wire will supply a varying voltage to the gauge, depending upon how much oil pressure there is.

I don't have the pinout in front of me, however.



Thanks man! I can figure out all of this with a multi meter. The one that's hot while running, and cold when the car's off but turned to on would be the 12V switched. Third wire would be a variable amount of voltage, AKA not 12v while running. I'm pretty sure I understand all that. I'll read the instructions for the gauge when I get home, should be easy enough to figure out.
olejoedad MAY 20, 06:42 PM

quote
Originally posted by robmox:


So if I hook up my multimeter, I should get 90 ohms for supply, 0 ohms for ground, and something in between for oil pressure signal?



Not at all.

The only wire you need for the signal is the center wire at the oil pressure sensor plug.

Does your new gage come with an oil pressure sending unit?
robmox MAY 20, 08:50 PM

quote
Originally posted by olejoedad:


Not at all.

The only wire you need for the signal is the center wire at the oil pressure sensor plug.

Does your new gage come with an oil pressure sending unit?



I bought the sending unit and gauge so I should have everything I need to diagnose the problem.
olejoedad MAY 20, 10:40 PM
Remove Fiero oil pressure sending unt

install new sending unit

Run wire from new sending unit to new gage (tan on Fiero plug - center)

Install new gage.

Attach sending unit wire (C203-E tan wire if using wire from Fiero oil pressure plug)

Wire up power and ground to gage.

You don't need the other two wires on Fiero oil pressure plug.

[This message has been edited by olejoedad (edited 05-20-2022).]

theogre MAY 20, 10:57 PM
Sender pins...
See my Cave, Oil Sensor
Gauge pin "reads" 0-90Ω to ground @ sender base.

Gauge can lie for many reason and wire from gauge to sender often won't help.

Oil Fuel and Temp shares same issues... And 1 or all can have problems at same time.
Gauge read off for iffy ground(s) anywhere. Iffy power won't help either.
Gauge have a resistor "bolted" to it and crap connection reads out or doesn't work.
same bolts have SS clips to connect to back board of dash and these clips and back board have problem w/ corrosion, plastic warping and compression...
Then back board have big plug to "see" the rest of car and they get iffy too.

Test oil/fuel w/ resistors to eliminate the sender. You can to that @ the sender plug and back of dash.
Anything close to 45 & 90Ω will do if using standard fix resistors.
http://www.fiero.nl/forum/Forum2/HTML/138175.html Instrument panel bulb layout
Back of aux gauges for GT but don't have wiring right now.

Do Not Trust Haynes rags when fixing a car.
Alldatadiy.com have same data as FSM for whatever year of GM and other cars. Is from Alldata.com is where many shops get data way back when only came on CDs later DVD to reduce media storage issues.
Even then has same errors etc in FSM but not the hot mess that Haynes often are. Chilton is only a little better.

------------------
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 Ogre's Fiero Cave

[This message has been edited by theogre (edited 05-20-2022).]