Ok Im working on my 70 Roadrunner and got the gauges out of the car. Had them in a couple of days ago and none of them worked! So i decided to remove and see whats going on. I hooked my 6volt battery charger to the back posts of each gauge and they spiked up, so now I know the gauges do work. On the ALT gauge they bypassed it for whatever reason. How do I check the ALT gauge while out of car? I just OHM'd it out, but dont know if thats correct. Figured as long as no open circuit its working???? Please let me know on that. Now that still doesnt solve why the 3 gauges dont work in car. The pins on back are nice , no corrosion or breaks. Circuit board looks fine as well. How do I test the Voltage limiter on back while out of car? Is there a way to test and make sure its function is ok? Id prefer to do all this while its still out of car. Also, any way to test the circuit board? Happy holidays and I hope I get some responses as I want to get my gauges working before I start the new engine so Im not "blind" to what my vitals are doing while running. Thanks guys!

Don't know how to check it out of car, but I would check all grounds/connection before you put it back in. May just be corroded.

sounds like the ammeter is good it should have a very low ohm reading,
the voltage limiter can be tested too. one of the 3 prongs on it will go to ground one will feed the volt and fuel gauges the last will go to the pins that the wires hook to. hook the ground to the gauge pod, 12 volts to the pin on the limiter that goes to the wiring harness, then use your meter to see that there is about 5 volts coming out of the 3rd pin.

Yah I think it had about 2 or 3 OHM reading. Pretty low, kinda fluctuated. So On the Voltage limiter, can I just pop out the limiter and test by itself? Just hook up a ground to a pin, and also 12 volts to another of the pins and check the third pin to make sure it has reduced the voltage down? Thanks

There is a procedure to bench check gauges using flashlight batts. Don't recall if it's 'aa' or 'c'. Can't go over 5 volts. Also check circuit board carefully and pins and connector. Just keep in mind electricity needs clean paths to follow,power and ground sides. As far as v/lim, yes check as described. By looking at were it plugs into cluster, trace cir/bd paths to determine which pin goes to grd,12v and gauges.

Circuit board can be checked for continuity. Just trace out paths. again make sure pins on board not broken and plug not spread.

When checking the circuit board for continuity, be sure to titen down the small self tapping screws as these complete the ground circuit for each illumination bulb...


Just my $0.02...

The circuit board is missing one of the black screw in bulbs, would this keep the gauges from working? Just wondering if the bulbs are all needed to complete the circuit?? Or do they have nothing to do with the gauge functionality? Thanks

Did you find Your problem and what was it?

https://board.moparts.org/ubbthreads/showflat.php?Number=5550004 for more info....check out the third post...