Oil and Temp Gauges Maxed Out

[scottthomp]

I just replaced my instrument panel voltage regulator. First thing i did was ground the wire to the fuel sending unit. The gauge pegged out at F. I plugged it in and it reads almost full. So I think it is working.

The oil and temp gauges, on the other hand, max out immediately when i turn the key. I have no clue what is wrong with them. Any ideas?

Is there any way to check them to make sure they are working?

 

[mustangmike6996]

there must be a short to power somewhere in those power feed wires. use a DMM and check voltage the gauges obviosly work you just need to go over the wiring

 

[scottthomp]

Ok i did more investigating. All 3 gauges have 11.8 volts on the black/green power wires going to them. The oil gauge stays at low with the key on but switches to high when i start the engine. Any ideas now?

The temp gauge started at low and as the temp warmed up quickly went to hot. I know its not that hot because i can still open the radiator. I checked the resistance of the sender. It was reading 140 ohms when warm. Then dropped to around 100 when it got warmer. The gauge read fully hot at both locations. Is it my gauge that is bad?

Thanks for the help.

 

[JamesW]

You should have 5V going to the gages. Your CVU is bad

 

[scottthomp]

OK, I got another new instrument voltage regulator. Turned it on and now its even weirder. The oil pressure gauge seems to work great, centered out around the middle, and it was peggin out before. The gas gauge moves a tiny amount when the power is turned on. The temp gauge does the same thing, at warm i t moved slightly but still read cool.

But, the gas gauge read above full when i grounded the sending wire, but barely moves when i plug it back in.

I tested the voltage coming off the regulator. It jumps around like crazy, from 0 to the highest i saw was in the 7's, but mostly 0 to 5 range. Shouldnt the voltage be constant?

Please help!

 

[chromedog]

if it is the factory style cvu, no, the voltage wont be constant... your best bet is to go to a electronics supply house, and pick up either an Lm 340, or an Lm7805 voltage regulator, they provide 5 volts all the time, and they are only 5 bucks at the most. you will need to solder two pigtails onto them (the package tells you which terminal is which) screw them onto your cluster, and plug them into your wiring. btw, the factory cvu is some sort of thermal switch and 5 volts is only an average, not constant voltage.