1971 GMC temp gauge
 

i just installed a new speedo in the dash panel 1971 gmc works good ...but now the temp gauge goes all the way over past hot .. What did do?? the temp was woking fine untill i unplugged the wiring from the rear of the dash panel

Re: 1971 GMC temp gauge
 

Was the battery disconnected when you pulled the dash apart? It sounds like your gauge took a spike and shorted out.

Re: 1971 GMC temp gauge
 

the gauge will go back to normal if i did connect the battery

Re: 1971 GMC temp gauge
 

:confused: Can you explain a little further? Does the gauge go back to normal if you connect or disconnect the battery?

It may be shorted directly to ground. The sending unit acts as a variable resistor to allow more current as the temp goes up.

Another problem could be the dash connector. It has a lot of flat lands that can get bent or broken when removing and reinstalling the connector. Be sure and check that carefully. If they looked damaged or broken you may have to replace the flexible circuit board.

Re: 1971 GMC temp gauge
 

yes i think it is grounded do not see where it is picking it up?/ the cconnector on the back plane looks good ?? if i remove batt. the gauge goes back to normal as soon as i complete the ckt it peg's looks to me like a solid grd??

Re: 1971 GMC temp gauge
 

Disconnect it at the sending unit and see what happens. Sending unit can be in almost any location on the engine depending on which one you have or if someone has swapped engines in the past.

Turn the key on and see if gauge goes back to normal cold position with it disconnected. If it does, it's probably the sending unit gone bad. The sending unit is like a door to ground for the gauge. As the temp goes up it opens up more. If it's open all the way, the gauge is pegged on hot.