Idiot Lights to Guages Swap?

[maufderheide]

I bought the GM guages to replace my GM idiot lights. The fuel and the volts seem to be working but the oil and temp are out of wack. How do I go about fixing that?

 

[Bonnewagon]

Did you change the sending units? They are different from the idiot light senders.

 

[rusty]

I just did the same swap and have the same problem. I am going to look into the sending units. They were changed for gauges but I am running a BB and have to find out the compatibility. Let me know how you make out.

 

[Bonnewagon]

OK, that said, did you verify the wiring at the harness? Some cars like my Bonnewagon, the factory had all the wiring in the right place for either gauges or lights, just plug n' play. Others, the wiring can be off by a wire or two, causing the problems. All years were not the same wiring pattern either. I remember swapping gauges into a Firebird and having to rearrange quite a few wires to get it right. You can push the pins out of the harness by depressing the locking tab with a tiny tool like an awl. Thank God I had the factory manual with the wiring diagrams to go by.

 

[JBreu]

Check here.I think they have it pretty much covered http://www.maliburacing.com/gauge_conversion.html

 

[Bonnewagon]

Great link, JBreu!

 

[rusty]

Yea, I followed the malibu racing diagram. Seems the temp is way to high and the oil pressure stays pinned at 60 lbs. Is it possible the senders are off? I got the V8 ones for my year mino 1978, but the motor I have in it is a 427 1969 vintage. I see they sell different sender units for different years and motors. Also My gauge cluster came out of a 1979 or 1980 mino, wondering if that is a difference also. Anybody got any ideas.

 

[Bonnewagon]

Motor doesn't matter, temp and pressure are universal. Only difference would be thread size maybe. Did you do the standard tests on the gauges, meaning ground to the sending wire should peg the gauge in either direction? If so then I would check the sending units with an ohm meter. See if the resistance changes as temp/pressure changes. Also test the wires between the sending units and gauge harness, could be some problems there too.

 

[rusty]

Hey bonnewagon, What is the correct way to check the dash gauges. Did you mean ground the sending wire with the key on. Not sure. Thanks.

 

[Bonnewagon]

Rusty, the correct way is to put a calibrated resistance on the gauge sender wire and see what it reads. Not many guys have that tester, myself included. A quick and dirty test is to touch the sender wire to ground, and then nothing (disconnected) with the key in the "run" position. It should peg in either direction if the gauge is good. How cool is this tool?