Electrical Charging Warn light stays on

KRUISR

5 Year Member
Apr 16, 2015
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So this started just the other day.

The charging warning light (battery symbol) stays on all the time. Stock voltage gauge works great and testing volts at battery while idling is 13.5-14.3 steady.

Thoughts on what issue I have.

Car is a 1990 GT with a 3G conversion done 5 years ago (about 15,000 km driven). All dash and wiring is stock (even stock radio). Added a dual wideband system and an aftermarket electric oil pressure gauge in A pillar a couple years ago.
 
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Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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Massachusetts
Factory manual doesnt offer much advice other than to have the alternator tested.

Only thing I can think of is to check for power on the yellow/ white single wire (would be wire 36 here). I’m sure it is as it appears the voltage regulator is working.

Also make sure the single white wire has a good connection. Wire 4 below, which would be the wire that was originally in the harness plug with the two #10 wires before you modified it for the 3g swap. I think a poor connection here does trigger the light

Short of that, no suggestions other than pull the alt off and have it tested.

C8FBD74A-1A3A-404F-B842-19C8A8D08E2E.jpeg
 
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KRUISR

5 Year Member
Apr 16, 2015
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Fixed it today. The connector at the alternator was loose. I disconnected the wire section from the alt to the first connector. I connected in a known unmolested wiring section I got from a 94GT and it worked great. Reconnected my original section and all good.

Also got the parking brake light working with a jumper in the connector at the MC. I have a '00 MC with a different plug so my OEM plug was just hanging loose in the area. I connected a jumper and taped it up and now that light works too. Just don't have sensing for low brake fluid.
 
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