I am trying to finish up my 4.9 project on my 87gt, and need to know where on the back of the instrument panel the c2 connector is, as there is three connectors on it, and also need to know which wires i need. What i am tryng to accomplish is to get the factory temp gauge to work. I temporarily have a mechanical temp gauge hooked up, but dont want any extra gauges inside car.

[This message has been edited by ss85fiero (edited 10-03-2007).]

i believe your looking for the left hand side back of the instrument cluster, the black connector with 12 pins/connectors.

Right about here:

Thanks for the diagram Hudini, but i am now a bit puzzled as i see that there is a wire on the c2 and the c3 for the temp gauge\indicator. Which do i use?

[This message has been edited by ss85fiero (edited 10-04-2007).]

Coolant temp indicator = overheat light. Gauge = gauge. These are the 2 wires you switch around to fix the "pegging temp gauge" needle. I will look for the exact instructions on doing this if you are interested.

Any info would be appreciated hudini. I am trying to figure out what two wires to hook up to the temp sensor that will make the gauge work. I no longer have an ecm in the vehicle due to the fact that the 4.9 i installed is carbureted, and the original wiring harness was a bit hacked up from a previous owner, so therefore, i am having to run wires from dash to the sensor.

Ok, you are using a sensor specific to the 4.9 or is it the same Fiero sensor?

The Fiero actually only uses one wire to run the gauge and one wire to light the overheat light. The ground is through the sensor itself which is why you do not use sealant on the sensor threads.

I would hook one wire to pin 13 on the C3 connector and run it out to the engine. Then another wire to pin 11 on the C2 connector and run it out to the engine. Then simply hook the wires to the 2 pins on the sensor. You have a 50/50 chance of getting the wires right the first time. If the gauge does not move when the engine is warm then swap the wires at the sensor.

To test the gauge you put a 1365 ohm resistor on the gauge wire and see if the gauge reads 100*F. Then put a 55 ohm resistor on the gauge wire and it should read 260*F. If it's off then pop off the needle and put it where it should be. A little pressure goes a long way.

If you need it the 1986 Factory Service Manual is available here: http://spad.sytes.net/fiero/manuals/
Page 972 shows the wiring diagram for the IP cluster. It also shows why the pegging temp gauge happens as the bulb test feature is wired through the gauge instead of the overheat light like it should.