The temp gauge is not working on my 87 240 There seems to be 3 or 4 what look like temp sensors on the engine. which one is the one that makes the temp hand on the instrument panel work? fuel gauge only works sometimes also. Any answers?

 

There is a 10-volt stabilizer, a silicone-controlled rectifier, at the rear of the instrument cluster. It controls the operating voltage to the temperature and fuel gauges. The voltage out of that SCR should be between 9.8V-10.2V. You can check it fairly easily with a multimeter by pulling the instrument cluster part way out.

Post back if you need further guidance on how to pull the cluster.