I have a 1986 F150, 4.9L , Manual trqansmission. The Temperature Gage is not reading. The IVR on the instrument cluster is working. Steady voltage on one terminal and pulsing on the other terminal. The Coolant temperature sensor is at the thermostat housing outlet. It is a TWO (2) wire temperature sensor. There is a Black with white stripe wire and a green wire at the connection to the sensor. The sensor has continuity across the two contact pins and when cold it is about 65 ohms and hot it is about 4.5 ohms. The wire at the insturment cluster conn

ection block that feeds the temperature gage is a red with white stripe. The gage itself has continuity across the two terminals and reads about 12.6 ohms.

All the wiring diagrams that I have found on the internet that seem to be for this model truck only show a single wire, Red with white stripe, going straight to the temperature gage.
With the key on, there is 9.5 volts on each of the wires at the temperature sensor which is very confusing.

I need some help figuring this out.

Thanks!

 

The 2-wire sensor is for the EEC. It has nothing to do with the gauge. The brass fittings with the spring-wrapped hard line appears to be for a mechanical temperature gauge.

On a 4.9L, the sender for the stock gauge is at the right rear of the block below the manifolds. It's very hard to see or reach.

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Thanks! So much! This must be where the problem is. I will check it soon!