Gang:
1976early...
Temp gauge worked now and then.
Recently, it stopped working all together.

I replaced the sending unit in the head. I used teflon tape to seal it.
Still does not work.

I detached the wire from the sending unit, put it to ground and turned the ignition key forward. The gauge went to all the way to 280.

Where is my problem as I have the new sender and the gauge tests ok??

 

Scotty-

Teflon tape should only be used on the first two or three threads of the sending unit. Teflon is not a sealer but rather a lubricant to make sure the pipe threads mesh together. When you load up the threads the sending unit may have lost its ground.

To do a simple test of the gauge, remove the wire from it and see if the gauge goes to cool... Then ground this wire out and see if the gauge pegs. If it does then the wire to the gauge is fine and the gauge is working.

Remove the sending unit and re-tape to the above specs and test again.


Willcox

 

Using the wire end from the sender touch it to ground as stated above THEN touch it to the brass case of the sender-see if the gauge reads differently-if it does read differently you have too much tape.
Otherwise your going to have to buy a good sender.

 

Your new sender is likely not the same range as required for your gauge.

I recently had to replace the sending unit in my Trick Flow heads. Since it was a smaller diameter thread in the aftermarket heads, I had to use a custom temperature sender. I couldn't find a sending unit that matched the resistance requirements of the gauge. Here is the procedure for what I did.

Step 1: Determining the resistance requirements of the gauge:
Went to Radio Shack and bought a $6.99 assortment of resistors, with many in the 80 ohm to 1k ohm range. Had someone watch the gauge (key on) while I connected various resistors between end of sender wire and ground. Determined resistance curve needed.

Step 2: Determining behavior of temp sending unit:
Found a small diameter thread sender (early-70's Ford and Jeep products) that had a room temperature resistance of 500 ohms. Threw it in a pot of water with the multimeter leads connected to it and heated it up. Took resistance readings of the sender all the way up to 212 degrees. Found that it went a little too low. I needed 80 ohms to read 220 degrees on the gauge (From Step 1), but the sender read 25 ohms (at 212).

Step 3: Solution
Snipped the sending unit wire and added 50 ohms in series. Now gauge reads in the right range. It may not be dead on, but I know where my temp is supposed to be and can see any fluctuations.

May be overkill, but might be helpful for you.

Good luck.