Hello All,
I have a 1985 22r 4x4 pickup with a temperature gauge that reads right below the overheating red zone within a few moments of the engine being turned over but the engine seems to be running at the proper temp. Any suggestions?
-GreasyHippy

 

Most likely the Temp Sender is going bad. It is basically a variable resistor that regulates how much voltage goes to your Temp Gauge. The more voltage the higher the reading. Normally as the coolant heats up, the Sender lowers resistance to voltage and allows more voltage to reach the Temp Gauge, which allows the gauge needle to move higher on the scale. Since yours is reading a higher temp than is actual, I would guess the sender is "out of calibration", either due to age/fatigue or some broken part inside it. The part is not repairable and has to be replaced.

These are easy to replace. It should be located near the Thermostat Outlet Housing and has a green plug on it. Here is a picture of one installed that I found on the web:



Here's the part for your truck: https://www.rockauto.com/en/catalog/...+/+sensor,4748

You should be able to also find the part at most local parts stores.

NOTE: Do NOT use Teflon Tape or any other sealant on the threads of the sender. The sender grounds through the engine as a part of the electrical circuit and using any sealant on the threads could cause the installed sender to not work. These senders usually come with either a copper washer on them or an O-Ring that does the sealing (see pics on parts page).

 

Ahhh...no...the green connector is for the cold mixture heater/emission control 'computer'. The disconnected brown connector, the one lying on the fuel pump hoses is for the temperature sender. The temp sender is the one about an inch to the right of that 'green' connector in that picture. The temperature sender will have an exposed male spade connection on it. A quick check is to disconnect that brown connector with a warm engine... the temperature gauge should go back to cold within seconds. DO NOT ground that wire as you're risking smoking the temperature gauge!