My 1990 super vr4 has had the temp gauge needle stuck up over max for years but the engine never overheats. I have always put up with it but if anyone has an easy diagnosis method or fix it would be appreciated. /ubbthreads/images/graemlins/confused.gif I also have a similar issue with the fuel gauge.

Change the sensor?

Check the gauge cluster wiring?

Check the wiring harness?

thanx 4 reply. it has done this with multiple gauge clusters. I just replaced the plug at sensor end which looked ok but under old insulation it was cracked freyed. Plug, bit of wire and some heat shrink and shes good as new. Thanks for the tips. /ubbthreads/images/graemlins/smile.gif Any chance the fuel gauge could be that easy?

Turn the ignition on and then pull out the fuel pump/sender assembly (leave the ignition on). Manually raise and lower the sender arm and check for any change on the gauge. You have to wait fro the changes as the signal is dampened so it's slow to respond. If you are able to go from full to empty on the gauge, then the sender had probably gotten hung up on a baffle in the tank and got stuck. If the range is partial, the sender is bad. Notice the where arm connects to the sender and the electrical connections there. Those wear out over time and will stop reading in some positions.

If there is no response on the gauge, then you could still have a bad sender but will require some electrical troubleshooting to make sure power is even getting to the sender and that there are no shorts in the wiring on its way to the gauge. Then there is the gauge itself which can rarely fail.

Usually a maxed out gauge reading is a short to ground in the wiring or at the sender.

Wiz

After replacing plug and dodgy wiring on the temp sensor on top of the thermostat the temp needle (which has been stuck over max for ages) finally dropped then after idling car for a minute or so it seemed to go up slowly. I assumed this had fixed it, however now it just starts at low then slowly makes it way up to over max again. I also replaced the sensor at bottom right of thermostat which supposedly controls the gauge and this hasnt worked either. In light of this i checked for dodgy wiring under the dash and tried a different gauge cluster to no avail. I then had someone test all the sensors around the thermostat and instead of it giving a low or odd reading indicating a faulty sensor etc, it indicated that none of these sensors are getting a signal?! does this mean that it is somewhere along the wiring loom (which doesnt look too broken or dodgy)or something not earthed or something that is earthed that shouldnt be? I have also checked all fuses which all seem to be fine. Need to sort it for peace of mind plus the car runs rich without these working. Then i can attempt the fuel gauge fix. Any advice much appreciated but bare in mind i am a newbie when it comes to electrics.

To answer your current question from some digging about on the internet, I'd say that if the wiring is the issue and the gauge pegs at the hot end of the scale, you are 'missing' a ground somewhere.

Since this is a persistent problem, the vehicle isn't actually overheating and you have confirmed both those sensors aren't responding, my money is definitely on the wiring/connectors/fuses.

I was going to suggest logging to see what coolant temp came up to ascertain if the temp sensor was working and the gauge cluster was faulty. I doubt in this case you'll get a temp reading at all if the sensor isn't responding. And again since you have tried numerous clusters with the same result my money is on the wiring/connectors/fuses!

I agree that its faulty wiring. Why not try running a jumper wire to the ground of the sensor and see if it gets the gauge to work.

I just read that you have running issues and dash issues. As the guys said above, the wiring stuff relating to the dash. If the ECM temp sensor is not wired properly, as there are two sensors - single prong dash/cluster temp and the two prong one that goes to the ECM, then you can have the ECU running and compensating for the improper engine coolant temperature.

Sort out where those issues start/finish for the gauges and likely you will be very close to your issue for the running issues also. Food for thought, as this is two separate issues but all those wires go back through the same looms.

it may be two separate issues, but if the CTS is reading that its at a certain temp, then the ecu will add a different amount of fuel to compensate for those temperatures. its like when you block off the FIAV and you get in cold weather, you need to hold the gas pedal for 3 or 4 seconds till the motor corrects for the cold temps.

I'm having some issues with my coolant gauge too. The original sensor goes immediately to the middle mark with the key in the ignition and stays there. Another used sensor warms up fine, but then at operating temp is goes and sits at the 3/4 spot.

I was reading through my 1990 Laser/Talon service manual and it says the sensor should read 104ohms +- 13.5ohms at 158*F. Does anyone know what it should read at say room temperature 70*F?