justin85xx3 Posted January 23, 2016 Share Posted January 23, 2016 My 72 Monte Carlo's dash lights for the gauges are not working. Both blinker lights work and the GEN gauge on the top left of the dash lights up, but nothing else works. I've checked all the bulbs and checked the fuses under the dash and everything looks good there. Do you think I have a bad circuit board or ?? Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted January 23, 2016 Share Posted January 23, 2016 What about the headlight switch? Quote Link to comment Share on other sites More sharing options...
justin85xx3 Posted January 23, 2016 Author Share Posted January 23, 2016 Headlight switch works, lights come on when I pull it out, I can turn it all the way counterclockwise and the dome light will click on, but never any gauge lights. Quote Link to comment Share on other sites More sharing options...
MCfan Posted January 23, 2016 Share Posted January 23, 2016 I recently found and solved a grounding problem on my full gauge dash that gave exactly the same symptoms. About three years ago, I converted my idiot light dash to a full gauge dash and installed LED bulbs. Everything worked beautifully until the gauges and dash lights recently all stopped working (headlights, blinkers and clock still worked fine). I first checked all the fuses and they were fine. Next I checked, cleaned and re-seated the ground wire to the dash frame and the ground washer strap behind the headlight switch. Finally I surmised that it had to be a faulty ground for the printed circuit itself. That ground screw is on the back of the instrument cluster just above the ammeter posts and can be accessed by simply removing the dash pad. Sure enough, when I installed the new full gauge circuit panel, I had failed to completely tighten that small hex head screw (see attached photo of the back of the dash cluster). I carefully snugged it down and everything magically worked again ... gauges and lights. Several years ago, I learned the hard way to disconnect the battery before messing with ANYTHING electrical, especially anything near the fuse panel or the instrument cluster so I would advise you to do the same. I was attaching the power wire to the dash clock that I had just repaired and my long nose pliers touched the edge of the printed circuit panel, grounding a power circuit and immediately frying the whole panel. I suppose it is possible that your printed circuit panel has also been fried, but I would sure check the ground screw first. Good luck! Quote Link to comment Share on other sites More sharing options...
justin85xx3 Posted January 25, 2016 Author Share Posted January 25, 2016 Making some progress. I unplugged the wires going into the headlight switch and re-plugged them in and almost all of the dash lights began working again. Must have been a loose connection. The only thing that is not working is the oil pressure warning light. The back-light works on it, but the red light never comes on, even when the key is in accessory mode (I'm pretty sure it's suppose to come on when in accessory and as engine is cranking up??). I checked that the blue cable is plugged into the top of the oil pressure sending unit under the distributor. I also removed the oil warning light socket and directly connected it to a battery and the light works that way. Some questions: 1) Is there a way to run an analog oil pressure gauge in the car without removing the factory oil pressure sending unit? Was thinking about mounting an analog pressure gauge somewhere under the dash. (I know they make conversion dash mount analog gauges but my budget says that will have to come later) 2) Is there a way to test the oil pressure sending unit or simulate a fault at the oil pressure sending unit to force the dummy oil light on? My thought here is to test the circuitry from the sending unit to the dummy light. Quote Link to comment Share on other sites More sharing options...
Leghome Posted January 25, 2016 Share Posted January 25, 2016 The previous owner of my 72 installed an after market oil pressure gauge in my car. Very simple hook up. fitting into intake next to the distributor and the gauge is mounted in the cluster with a small plastic tube connecting the two. I just replaced my circuit board also and no problems as I did nothing but replaced the board. Quote Link to comment Share on other sites More sharing options...
justin85xx3 Posted January 25, 2016 Author Share Posted January 25, 2016 The factory oil pressure sending unit is next to the distributor and I'd rather leave that in place and install a secondary analog oil pressure gauge using another fitting somewhere. Question is, does another fitting port exist on these engines? Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted January 25, 2016 Share Posted January 25, 2016 ground the wire at the sending unit, if the dash light comes on, the sending unit is bad 1 Quote Link to comment Share on other sites More sharing options...
justin85xx3 Posted January 25, 2016 Author Share Posted January 25, 2016 ground the wire at the sending unit, if the dash light comes on, the sending unit is bad Grounded with a wire to the alternator bracket and the light came on nice and red. Looks like I have a bad sending unit. Headed to the auto parts store tomorrow. Quote Link to comment Share on other sites More sharing options...
MC-71 Posted January 25, 2016 Share Posted January 25, 2016 Look just above your oil filter. You should see a plug. Not always. Carl Quote Link to comment Share on other sites More sharing options...
John S Posted January 25, 2016 Share Posted January 25, 2016 You can always install a 1/8" tee pipe fitting that way you can have both. I've done that many times. John S Quote Link to comment Share on other sites More sharing options...
justin85xx3 Posted January 28, 2016 Author Share Posted January 28, 2016 Well I got all the dash gauge lights working thanks to everyone's help but now I have bigger problems with the motor. Quote Link to comment Share on other sites More sharing options...
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