Ground location for the old oil Pressure and temp gauges

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PostPosted: Sat Mar 14, 2015 7:08 pm
Ok, I was able to start the car on the first try and decided not to let it run, as I haven't been able to get my old oil pressure and temp gauges to work. It was my impression that you didn't need to use the pigtail ground wire that was on the old style alternator. Now I am not sure this is correct when you are using the old gauges. The manual doesn't cover this to my knowledge. Can any one tell me where the old oil pressure and water temp gauges are ground? I am thinking it must be the pigtail ground and that is my culprit.

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PostPosted: Sat Mar 14, 2015 8:28 pm
I'm just going to give the basic to this. Three wires to gauge. One is power any power that turns off with master or ignition switches. Two ground and where,battery,chassis you can find that. Three wire that goes to sending unit. When all is connected right you can take the wire that goes to sending unit and touch it to ground,engine block,ect. and the gauge will go to max. This is with all wire connected to back of gauge and power on. Hope this is not to hard to follow. Wires must be on the gauge right sometimes you can look at back of gauge and it will tell you or goggel it.

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PostPosted: Sun Mar 15, 2015 11:11 am
My problem is not where the wiring attaches to the guage, that is correct. It's hard to trace the wires from the dash to the engine once you have done the installation. I am sure the temp and oil pressure wires to the signal are correct, so the problem has to be the ground. When you look at the dash wires going back to the engine, you have several black ground wires from the dash which includes those for the gauges. Then coming back in the same harness you have a larger black ground wire. At what spot in the back, do all the ground wires come together and what is the location on the gen 2 for this ground? Is it the pigtail on top of the old alternator or does it come back to the front with the larger ground wire?

My guess is that I could fix this issue by discontenting the ground wires directly from the gauges and run seperate wires to the new frame ground boss, but I am trying to use as much as the original dashwire harness that I can. Pat

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PostPosted: Sun Mar 15, 2015 1:23 pm
Does anyone have a wiring schematic of the gen 2? I checked my conversion manual it refers to a schematic, but none in the manual itself. I am just interested in the dash schematic to see where the gauge wires ground. Pat

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PostPosted: Sun Mar 15, 2015 1:38 pm
Pat I think that there is a set on Mumm Brother's website.
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PostPosted: Sun Mar 15, 2015 7:51 pm
Shouldn't matter where you ground since everything should be ground to chassis (assuming you have the proper ground from transmission to frame. The old black ground went the the engine block through a bolt that also had a small screw for the ground of the smaller ground wire(s). On the gen3, I had a couple of grounds from the old harness that I attached to the frame up near the coolant tank on an existing bolt.

BTW, do you have a laptop to run the PE3 software setup? You can confirm that you're getting the right oil pressure and water temp from those readings if you just want to initially check that the installation is working correctly (you need to do this at least once to set the throttle open/closed positions.)

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Bob Breton - SRF 51 - San Francisco Region
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PostPosted: Sun Mar 15, 2015 8:51 pm
I have always grounded anything from the dash to the bracket that holds the steering shaft. That's how the dash had been grounded when I got the car, and it seems to work fine.
Dan

Formerly Teamwork Motorsports #99, Chassis #460

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