Couple more wiring questions: Engine gauge harness I.D.

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ScooterDog

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Aug 7, 2015
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Location
SE Wisconsin
My Car
1973 Mach 1 Q-code


I bought this repro engine gauge harness for my 351 auto. I think the plug on the far left is oil pressure, and the 2 on the far right are coil+ and water temp. What are the other 4 plugs??

Also have an under dash question: can anyone tell me which wire is the main power source for all the gauges? I need to start troubleshooting there...

Thanks in advance, maybe this will be the year I get my car on the road!

 
I think those are for emission controls and carb solenoid anti-backfire lines. I could be wrong, though. They are definitely not required for running an engine.

 
It is not really that simple to go to gauges from lights. Took me months to find a harness that had not been hacked up. I will know tomorrow if it all works.

I could never tell you how to do it I just found the correct harness and changed them out, lol.

Each year is unique and vert or Mach, and all the other add on options.

David

 
Gauges have different power sources. An ammeter has two always hot leads that connect to the starter solenoid/alternator area.

Fuel, temperature, and oil pressure gauges are powered by a constant voltage regulator that has a resistor wire between the CVR and the ACC output.

Most indicator lights have a RUN-only or ACC source on one side and the signal on the other side of the lamp.

 
The fuel, temperature, and oil pressure gauges are easy to wire in. The hot (positive) side comes from the CVR, as Midlife said. The ground side of the gauges run to the sending unit. The ammeters are a shunted design and without the harness are a PITA. I have wired them up from scratch, but it took a lot of experimentation to get the gauge to read correctly. Length and sizes of wires are critical.

 
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