Gen 1 light stays on with key off

[dougco1]

Just took my 1009 for a nice 20 mile drive and when I got back and turned it off the Gen 1 light stayed on. Even with the key out. It starts fine, voltmeter reads in the green when running and gen 1 light goes out when running but comes on when I shut it off. Popped the hood and noticed alternator on drivers side warm/hot to the touch compared to passengers side. All else looked good. Would a short in the alternator send power back to the dash light?

Anyone have this happen? Any clue as to where to start troubleshooting?

 

[doghead]

Time to rebuild the alternator. Most likely item failed is the diode trio. Possibly the voltage regulator.
Either way, open it up and replace both. The diodes can be tested but not the regulator.

All components are inexpensive.

 

[dougco1]

Time to rebuild the alternator. Most likely item failed is the diode trio. Possibly the voltage regulator.
Either way, open it up and replace both. The diodes can be tested but not the regulator.

All components are inexpensive.

Thanks doghead, I was just researching and came to the same conclusion. I may just spring for a new AC Delco isolated ground $150.00 and get the original rebuilt for a spare.

 

[cucvrus]

Disconnect the batteries if you don't get to work on that issue. Back in 2010 we had a chassis field fire and 6 brand new cutaways burnt up from an internal short in the alternator. All 500 vehicles were towed to the dealer for alternator replacement and batteries had to remain disconnected during assembly and up fitting. Play it safe. https://repairpal.com/recall/10V138000 I would not risk starting a fire if it is shorted internally and making heat. Good Luck. Report Back.

 

[doghead]

If you buy one, be sure to test it with a meter to be 100% sure it has an isolated ground.

I always do, and also after a rebuild. Better safe than sorry.

 

[dougco1]

Disconnect the batteries if you don't get to work on that issue. Back in 2010 we had a chassis field fire and 6 brand new cutaways burnt up from an internal short in the alternator. All 500 vehicles were towed to the dealer for alternator replacement and batteries had to remain disconnected during assembly and up fitting. Play it safe. https://repairpal.com/recall/10V138000 I would not risk starting a fire if it is shorted internally and making heat. Good Luck. Report Back.

Disconnected them as soon as I found the alternator somewhat warm. Thanks

 

[dougco1]

If you buy one, be sure to test it with a meter to be 100% sure it has an isolated ground.

I always do, and also after a rebuild. Better safe than sorry.

Great advise. I think now I will just pull it and rebuild the original. I don't trust these new oe ones they have advertised.

 

[ehuppert]

Rebuilding what you have is a wise choice. Reman (and new) parts are ALWAYS a crap shoot. Had read in a trades publication a while back that 40% failure rate was acceptable on electrical parts. Well i do believe that number is correct based on "first hand" experience.

I would also guess diodes. Easy enough to check with the meter once removed!