1969 Bronco -temperature gauge goes to hot when key is turned to on position, but engine not started

[AZ Broncos]

1969 Bronco - Temperature gauge goes to hot when key is turned to on position, but engine not started. Put in new temp gauge same issue persists.

Oil pressure gauge also gets pegged out as high as gauge will go once engine is started within a few seconds. New filter and proper oil weight. New oil pressure gauge. Same problem persists.

Grounding problem? Voltage problem?

 

[AZ Broncos]

wire removed from temp sender unit - temp gauge does not move

wire removed from oil sender - pressure gauge does not move when engine is started.

 

[Yeller]

I'm making assuming this is a factory gauge cluster? have you checked the input voltage on the gauges? should be 5 volts, if it is 12, that is why they are pegging out when turned on. the other is the sending units are faulty or incorrect.

there is a voltage regulator on the cluster that if it has failed either there is 12v coming out or there is no volts coming out. sounds like you have 12.

I could be wrong this is just my theory.

 

[Viperwolf1]

Or the gauge cluster itself is not grounded.

 

[Bitch'nBronco]

Since its two gauges pegging out at the same time, I'd check to make sure the cluster has a good ground as Viperwolf mentioned.

 

[AZ Broncos]

It was oxidation on the ground terminal for the gauge voltage regulator.

 

[Yeller]

Nothing like an easy fix, glad I was wrong, that was easier.

 

[nvrstuk]

Gotta love easy fixes!

 

[jamesroney]

Nothing like an easy fix, glad I was wrong, that was easier.

You weren't wrong. You were mostly right. The voltage regulator was putting out +12V.

The root cause was NOT an un-grounded cluster. It was an un-grounded regulator.

You did use the disjunctive "or" with regard to the sender nonsense. So I'm giving you 90% credit. That's still an "A."