# 69 GTO Rally Gauge issues



## MrAllthat (Dec 9, 2011)

I have a 69 GTO that possibly had the rally gauges added later in its life. When I first bought the car only the fuel gauge worked. I diagnosed the oil pressure gauge as a faulty sender. I replaced the sender and it worked well for a while, but then it crept up higher and higher (the average oil pressure) until the gauge just stayed pegged again. I measured the resistance at the pressure sender and it is showing an open circuit with 0 psi of oil pressure (engine off). Could this be just a bad replacement sender or another wiring issue that cooked the sender. 

The car was "converted" to an internally regulated alternator too. The wiring is all wrapped up and not done the way I would have done it. It runs fine and the alternator works fine, but the gen light stays lit. If I pull the bulb for it, it kills power to the fuel, oil and temp gauge. Are these supposed to be getting their power through the gen bulb?
Another problem (im assuming these are all linked) is that the temp gauge doesn't do anything. If I ground out the sender wire the gauge doesn't move, it just stays pegged at 250. I assumed it would have power if the fuel and oil pressure do. 

I am just really confused by this whole deal and don't want to throw money at a new wiring harness and possibly circuit board.

So I guess the two big question are:
Do the rally gauges run on 12v or are they supposed to run on less?
Does anyone have a pinout diagram of the rally gauge circuit board connector?

Thank you for taking the time to read and hopefully answer.


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## pontiac (Mar 6, 2011)

bad oil pressure sender. wrong temp sender need to properly wire alt. so gen bulb is not energized likewise, senders do not run on 12 volts, there are the grounds for the gauges. gauges run on lower voltage than alt. puts out. Gen circuit acts as resistor to reduce voltage to dash panel. Ralley gauge circuit connector is exactly the same as non gauge only only wires run to different senders, except for a tach.


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## porkandbeans (Jul 24, 2012)

I'm curious about this too. I have the rally gauge on my '69, and I have had issues with the oil pressure gauge also. I've replaced the sending unit 2 or 3 times. Each time, the new sending units would work for a little time and then the gauge would flutter big time. I occasionally use a backup gauge to check up periodically.
The rest of the cluster works find . . . other than the occasional light bulb that is also on my list.


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