Camodica

I have a 87 pontiac firebird formula with the 350. My gauge cluster is only half working. The speedometer and tachometer and indicater lights work but my oil, temp, battery and now the fuel gauges arent working. I did what i probably shouldnt have but i took the cluster apart and switched the little motor things that control the needles on the cluster to see if that worked and thats when the fuel gauge stopped working. Before i did that, i changed the temp sensor and the thermostat and still nothing. Do i need a new cluster? Please help me as this is driving me nuts. Thanks charlie

gearhead141

You may have done more harm than good. Were there any conditions that caused it to be inoperative before you removed the cluster? My trouble-shooting always starts with: what was happening at the time things went haywire. So, if you can remember what you were doing with the car at that time, it will give you a starting point to work from. Another handy tool is the factory service manual (FSM) trouble shooting tables. As far as the cluster is concerned, you may need to have a shop that works on speedometers check it out. Unless of course you are confident in your abilities to assemble it back to working order.

Camodica

Just the temp gauge and the oil one werethe only two that were screwed up from the start. Thats how i bought it. But now the oil is working and the volt and temp arent working

QwkTrip

iTrader: (22)

This is odd I should know this, but it just so happens I had to trace out every damn circuit of the gauge pod this weekend in preparation for installing aftermarket gauges.

It just so happens that speedo, tach, and turns signals use the same ground trace on the printed circuit board and ground at Pin 2 of the BROWN color connector. And you guessed it.... oil, temp, volt, and fuel gauges all go to the same ground through a combination of Pin 2 and 12 of the BROWN connector.

Given your symptoms, I would guess the ground for your non-working gauges is interrupted somewhere. Check for a tear in the green sheet (circuit board), a loose connection at the connectors, and clean up the surfaces of the connectors with a pencil eraser. Also do an electrical continuity check of the wire to chassis ground. If the electrical resistance is high then the ground wire and/or connection needs to be repaired somewhere in the harness.

Camodica

Ok thanks ill look into that next time i plan on working on the car. I appreciate all of your help.
-thanks charlie

Camodica

Hey qwktrip, what exactly is "pin 2"?

QwkTrip

iTrader: (22)

Electrical connectors have a number embossed in the connector next to every electrical terminal. You'll see it on the connector itself. The electrical terminal is often called a "pin".

Camodica

Ahh, ok ill check it out next time i head out to the garage. Thanks again

Camodica

Qwktrip, your talking about if i have the cluster out, im looking at the back and where it plugs into the car on those copper lines? Im sorry for sounding dumb lol

TTOP350

iTrader: (8)

I have had several clusters that do random weird things. Here is a good tip for a car that sits or has sat most of its life.
I take the cluster out, remove all the screws (not all at once) that are going through the circuit board for the gauge power/ground/signal terminals, use 000 steel wool on all the brass/copper contact points and esp on the brass where the electrical plug goes in the back. Carefully blow off the fine steelwool that's left.
Its amazing how accurate and how well the gauges work after that.

Camodica

Ttop350, thanks for the advice, ill try it today after work. Also i have another question. On the radiator, the driver side fan stay on all the time, from the time i start the car up till i shut it off and the passenger side fan doesnt do anything. Any thoughts on this issue?

TTOP350

iTrader: (8)

Stuck relay or ground in the ecm ? driver side
Bad fan switch, bad relay or bad fan motor. pass side

Camodica

Ttop350, thanks for the help. Ill check it all out after work

Camodica

Hey qwktrip and ttop350, i just tested that i have power at the gaugs but still nothing. Do you think a new gauge cluster would fix the problem?

QwkTrip

iTrader: (22)

The only thing common with the gauges you mention is the grounds. If you had a power problem then it would affect all the gauges.

Camodica

But remember i did switch the mechanism's that control the needles around too like a dummy tho 😣

Camodica

Hey qwktrip, how many of those pins behind the cluster should be getting power? I have one from the upper plug and one from the lower plug that is getting power.

QwkTrip

iTrader: (22)

I think this is what you're seeking. This is for '88.... can't guarantee it is the same for your '87. It is all I could find, and I felt lucky even finding that!

C1 is the BROWN connector (lower), and C2 is the GREY connector (upper)

https://www.thirdgen.org/forums/elec...ml#post6110270

Camodica

Awesome thank you!!!!