Electrical problems

BarryG

BarryG

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Nor*Cal - Rocklin, around the corner from Dan
I went to take my Coupe out and I had a drained battery. Charged it up and thought everything was good. But why the dead battery?
Started up and pulled it out of the garage. Went to shut if off and the engine keep running.
That’s a first

Any thoughts

Thanks
 
First thought: any work done on the car since the last normal start/stop?
Type/year of car?
 
Sounds like you are backfeeding positive voltage into the green circuit even with the key off or when you turn the key off the green circuit is staying hot. You can test that with a voltmeter.
 
I have repeated this several times over the past year or so. One common point for the battery and ignition is via the hazard switch. The hazard switch has both BATT and ACC power (because the turn signals work in the ACC position, and the hazard works all the time, so it is connected to BATT via a fuse.

The failure mechanism appears to be that the hazard switch shorts internally and powers the green/white wire. This goes to the fuse box, where two fuses are tied together at one end. One is the green wire, and the other has the green/white wire. If this short occurs in the fuse (has happened to me twice on my 635) the green/white wire powers the green wire, and everything works regardless of the key position. Note, if the steering column is not locked, this is also a way to hot-wire the car... , so the steering column lock is really the key antitheft device...Try pulling fuse 5 or 6 (depending on which direction you count from).

Here is the path: (I show this to the ignition switch green wire for convenience, but that also goes to the coil ballast resistorVia the little "2" connection)

Screenshot 2026-06-01 at 7.43.35 AM.png
 
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Bad Voltage Regulator, possibly, just the clock will drain the battery over 6 months if not on a tender.

If the battery is dead, it may be too far gone to hold more than a surface charge. Buy a new battery & should cure your electrical gremlins.
 
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BarryG said:
@ScottAndrews you got it

My alt “red” light was glowing
I pushed the hazard switch and the alt light went out. Started it up and shut it off… now. I need a new Hazard switch

Thank you guys for all the help
Click to expand...
Yup!!! Terrible design, that switch!
BarryG said:
I removed the green wire from the fuse box and it started up but again it will not shut off

The green wire is Hot

Is there a relay I can check
Click to expand...
There are multiple "green wires" going to two of the fuses...If you look at the diagram above only one of them finds its way to the coil.
 
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