Ford 335 temp

[Koppyscott]

Nearing the end of my “new to me” project, a ‘77 Ford 335. As soon as I start the engine the temp gauge goes straight to red hot. Is this a sensor issue or an electrical gremlin? When I got the tractor the green temp sensor wire was twisted to another blue/purple stripe wire. The schematic said where the green wire belonged but the other wire remains a mystery but it made me wonder if the sensor was bad and this was someone’s way of making the warning light go away?

 

[Jim.ME]

Welcome to the forums. You might have better luck if you post this question on the Ford Forum.

You could try suspending the sensor probe in a pan of water and heating the pan. Use an ohmmeter to see if the resistance changes as it warms. If you have the correct service manual for the tractor sometimes, they give the resistances for sensors.

 

[Destroked 450]

The blue/purple strip wire is for front head lights if you have them
Disconnect the sender wire and turn the key on, if the temp gauge moves you have a short in the wiring or the gauge cluster is not wired correctly
If the temp gauge doesn’t move until you reconnect the sender either the sender is bad or mismatched to the cluster your using