Hi everyone, first time owner here, just purchased a 1981 with a few small mechanical issues. Really enjoy this site and appreciate all the help that everyone provides for us newbies.

Today I’m attempting to repair a non-functioning coolant temperature gage. Car runs fantastic and I’ve spent hours driving it in bumper to bumper traffic in over 90° weather and I had no overheating issues. It looks as though the only non-OEM components are an aftermarket Pro Comp intake manifold and a Holly double pumper carburetor. I’ve been doing a lot of searching and reading online to get an idea of what I need but I’m sure, with some help from here, I will avoid some mistakes.

I’ve tested the actual gauge and have determined, with the help of Willcox site, that the gauge is functioning properly. I connected the signal wire to ground with a 200 ohm resistor and got a temperature reading of approximately 150°. When connected directly to ground, the gauge maxes out. One slightly confusing part is that my resistor mounted to the back of the gauge reads 51 ohms. If I read correctly, the Willcox site says that should measure 90.

Under the hood there’s only one temperature switch installed in the intake manifold on the driver side. This is a single blade type switch that closes when the engine temperature goes above approximately 220°. It is not a variable resistance type sensor. They had a black w/ light green stripe wire connected to this. Looking at a wiring diagram from a 1980, assuming it’s the same, this wire should be connected to an idle stop solenoid(???). The dark green wire that goes directly to the temperature gauge is hanging disconnected. There are plugs in the head where the other temperature sensors should be located. One towards the front of the engine on the driver side and one towards the rear on the passenger side. I’m trying to find the correct temperature sensor that will provide the correct resistance directly to the gauge(0-800 ohms?).

There’s also other wires hanging disconnected that I’ve shown in the pictures that I need help identifying. Sorry about the dirty conditions, haven’t had time to clean the engine area yet.

Again, thanks to everyone here that have already provided the info needed to get to this point.


Temp switch

Unknown connector

Unknown connectors

 

EGR/AIR pump connectors, looks like you don't have that any more.

Do you have cast iron heads? If you do just get a OEM sensor from Wilcox that will fit your intake or the head. If placing the sensor in the intake put it near the thermostat.

 

I do have cast-iron heads, I’ll probably install the sensor there.
Thank you. I really appreciate the help.

 

.You say you purchased an 81 then say you used a wiring schematic for an 80, they are not going to the be the same as the 18 had a computer controlled carb and the 80 did not. I understand the CCC has been removed but the wiring harness is still in place and you need to confirm the underhood harness did not change between the two years.