Idiot lights


Jan 16, 2020
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Pittsburg, Tx, USA
This may seem like a dumb question, but has ANYONE wired up (or known of) an alternator idiot light for a 73 C-body before?

I'm ripping out the dash assembly and installing a complete aftermarket gauge set to go along with my Musclecar Makeover. 6 gauge setup with a 200 MPH GPS speedo (w/turn signals & hi beam indicator), 8k tach, volts, oil, temp & fuel (73-10 amp of course), PLUS a matching clock for a total of 7 gauges. I've already yanked the extra plug in the water pump housing to mount the temp gauge sending unit, allowing me to keep the Hot/Cold idiot light sending unit, and the aftermarket sending unit for the oil gauge is a dual lead unit with 1 for the gauge & the other for a light (comes on at 11psi or less). The factory ammeter leads behind the dash are shorted together and taped off with a heavy cable going from the hot lead on the 130 amp alternator (because I'm running electric fans, fuel pump, MSD Ignition & an 800 watt sound system) wired direct to the battery to prevent the bulkhead connector from overheating. The only issue I'm running into is how to wire an idiot light for the alternator. I want a His & Hers dash, gauges for me and lights for her. I've been looking online, but for this style of alternator (2 field wires & external voltage regulator) Ma Mopar only wired up the dashes with an ammeter gauge, no idiot light.

Any ideas? Pics would be a big plus and earn you my deepest respect. Thanks in advance


Senior Member
Aug 9, 2017
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Dublin, PA
The charge indicator lamp in cars that are so equipped is controlled by electronics inside the voltage regulator.

If you hadn't already invested in a high output alternator, a fairly simple solution would be to install a GM alternator on the car that has an internal voltage regulator and charge lamp circuit.

Your best option would be to build this simple circuit to control a warning light. It's adjustable, so you can choose the voltage at which it goes on.



John Kirby

Active Member
Jun 3, 2016
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Minneapolis , Mn
Idiot lights have their purpose. My son's Durango has the dash buzz loudly and the display says "CHECK GAUGES!!" in bright red text. If there is an issue. Had the oil pickup clog up and this saved the engine. Gauges are useless if you are not looking at them. It's also why cars now have a low fuel light. When was the last time you saw a car on the side of the road out of gas?