camarocrzy

The temp gauge on the dash doesn't move. Ill have the car at operating temp,turn the car off,then turn the key without starting and the other gauges move but the temp gauge wont. Is this an easy fix? Do i have to splice a new sensor in? I have never messed with sensors . Could this be the reason why my fans seem to constantly be running and my coolant boiling? I just checked the wiring to the sensor in the engine and it was ok do i just need the sensor?

Injuneer

The temperature gauge has nothing to do with the PCM fan control system. There are separate sensors for the PCM (water pump housing) and for the guage (drivers side head between #1/#3). If the temp gauge is sitting at the low end, it means there's a large (or infinite) resistance in the system, which could be the wire off the sensor, or a faulty sensor. You don't "splice" in anything... there's a connector on the harness wire that pushes onto the sensor.

Pull the harness connector off the temp sensor in the head, and key-on measure the voltage between the harness wire and the engine ground. Should be 5V. You can check the sensor with an ohm meter, to decide if you have to replace it. When you do replace it, you will lose coolant, and you will have to bleed the air out of the system. If you need the correct resistance readings for the sensor, they are in my online scanner writeup:

http://members.aol.com/InjuneerZZ/ScanMast.htm

camarocrzy

What do i need to measure the two? How do i do it? Sorry, i such a newb!!

Injuneer

You need multi-meter. Pull the harness wire connector off the sensor in the head. There's a single pin in the connector. Set the meter to "DC Volts" Clip the red lead of the mult-meter to the pin in the connector, and touch the black lead of the meter to a good ground, preferably on the engine block. Should see +5V.

If you have 5V on the pin in the connector, leave the connector off. Set the multi-meter to "Ohms". Clip the red lead to the pin on the sensor, touch the black lead to the engine ground. Should read:

Coolant temp: 68degF = 3,520 ohms
86degF = 2,238 ohms
104degF = 1,459 ohms
122degF = 973 ohms.

+/- 10% on those readings will be OK.

camarocrzy

WoW, Thank you so much!! I love this site!

RestoRoc89

My temperature gauge also doesn't seem to work. It never moves and just stays at the lowest reading. I checked the voltage at the connector and I'm getting 12V. What could cause the voltage to be too high? Is there a regulator for that circuit somewhere? To provide some extra information, my car is a 1993 Z28 and the tachometer in my car also doesn't work (flutters between 0 and 1000RPM regardless of actual engine RPM). Could this simply be a guage cluster problem? The temperature gauge worked fine last week and seems to have quit after an Optispark install (I never touched the sensor in the head or the affected wiring). Thanks for any help.

Injuneer

You might be OK with +12V on the single wire to the sensor in the head. The +5V is the correct number for the PCM sensor in the water pump, but the gauge may well run off of 12V. Could be my error.