I have a 1987 5.0 GT. My problem is that my water temp. gauge stopped working. I am getting a low voltage reading at the wire on top of the sending unit. I am stumped, please help.

 

............do you know how the sending unit works????.......the gauge reads a resistance value fron the sending unit and the higher the resistance value it reads...it interprets this resistance reading as a cooler value hence your gauge reads cool/C....the lower the resistance value signal from the sender to the gauge the warmer it reads on the gauge..so resistance is inversely proportionate to the reading on the gauge..meaning as resistance goes up temp gauge goes down..and as reistance goes down/car warms up gauge goes up.......the correct sending unit for the cluster is a single wire one on the left front corner of the intake not the two wire one for the ecm on top of the coolant rail

 

now the ect for the ecm will have a voltage reading on the signal return..... because The ECT receives the “Signal Return� voltage from the EEC, then allows a certain amount to return back to the EEC....but this is the ect for the ecm located on top of the coolant rail....I assume you are checking the wrong one as the other one/ single wire one is for the gauge....anyway replace the water temp sensor and the gauge may work again

 

I am testing the single wire sending unit. Thanks for your help