Technical Please help with temp gauge

I am stumped...I am replacing the temperature gauge and sending unit in my 56 F100 with a gauge and sending unit set from Mid Fifty, but for some reason I just cannot get it to function. When I connect the 3 wires from the truck (ground, power, sending unit) to the gauge outside of the dash it registers. As soon as I screw the gauge into the cluster, it stops working. I have no idea where I am messing this up at and cannot figure it out. If anyone has any suggestions, please let me know.

 

Maybe it's grounding it self out.

Sent from my SM-G930T using The H.A.M.B. mobile app

 

Is the truck, or the gauge set positive ground? That will screw you up, in a hurry!

 

Remember that 1956 was an oddball year for Ford. It was the only year Ford used 12V gauges. They used 6V gauges from 1928 until 1985 except for the 1956 experiment. After 1956 they went back to 6V gauges and used a voltage reducer. Since your truck has no reducer, you must use 1956 gauges only or install a voltage reducer to read correctly and not toast the gauge.

 

try hand tightening the nuts on the gauge. maybe the housing is warping and causing problems inside. i just heard a friend tell me he had the same problem and that cured it.

 

Is the gauge cluster grounded ? That may affect it ,as you said three wires. I thought that the sender and power were the only wires needed. the sender acts as a moving ground. no? Good luck Jack

 

The truck is definitely negative ground

I'll have to check if the cluster is grounded. The original gauge was the two prong (power and sender wire). The one I got from Mid Fifty was the new gauge and sending unit set http://midfifty.com/item.php?INV_ID=5116&PN=Temperature-gauge-and-sender-kit-with-1-8-npt-sender-mf that has the three connections for power, ground, and sender wire.

It's weird because if I wire it up outside the cluster it works, but as soon I install it in the cluster it stops working.

 

The original gauge was grounded by the cluster, the new gauge is grounded by the black lead on the gauge. The temp sender grounds through the block. For it to work you must not use thread sealant or tape on the sender or it will affect the grounding of the unit. The block must be properly grounded as well.

The temp gauge must be used with the correct sending unit. Yours, according to the instructions should register 105 ohms at 160 degrees. Hope it helps.