My gen light came on winching

90Pioneer · Aug 30, 2006

I have a '96 XJ with an Optima deep cycle blue top and a Warn M8000 winch. Factory alternator with 87k miles.

I was winching my buddy out on a trail. It had a bunch of loose dirt which my tires spun around as I was backing up to get into an appropriate winching angle.

I winched him out, and it was all of maybe 2 or 3 minutes of serious winch use. During so I was revving up the engine to 3 or 4k. Afterwards I had noticed my GEN light came on beside the check engine light.

My battery gauge was reading a normal 13.5 volts. After seeing the light I turned everything off then drove home about 12 miles. The gauge stayed right at 13.5 volts the trip home.

After arriving home I turned the engine off and I restarted. Now the GEN light went away.

Any idea why the GEN light came on, but then went off on the next engine start? Do you think the loose dirt thrown at my alternator could have momentarly affected it?

5-90 · Aug 31, 2006

The GEN light (alternator state of charge, to be technical) comes on when the system notices NEGATIVE amperage coming from the battery - meaning, the battery's being drained. Since you were running a winch, this is not unexpected - I think typicaly winch draw is somewhere around 200-300A, while the highest output OEM alternator might touch 120A. Therefore, you were winching off of your full alternator output, and the shortfall was being made up by the battery.

This would give you a GEN light. If you had an ammeter instead, you'd see it on the negative side of the scale for a little while.

Since your battery was rather drained by the pull, the alternator continued to run somewhere near full output for a while to charge the battery. This would have stopped once the battery was fully charged again.

The GEN light will NOT illuminate after the next KEY-ON cycle, provided the battery was good (which is apparently was.) The GEN light does not respond to "hard codes" like the MIL/CEL (Maintenance Indicator Lamp/Check Engine Lamp,) but you may have a "soft" DTC (Diagnostic Trouble Code) set in the PCM (Powertrain Control Module.) "Soft" codes can be reset with a reader, or will clear themselves after a predetermined number of engine start cycles (the engine is started and comes to operating temperature.) "Soft" codes do NOT illuminate the MIL/CEL.

So, nothing for you to worry about. I realise I could have just said that to begin with, but what would you have learned from that?:laugh:

5-90

90Pioneer · Aug 31, 2006

5-90 said:
The GEN light (alternator state of charge, to be technical) comes on when the system notices NEGATIVE amperage coming from the battery - meaning, the battery's being drained. Since you were running a winch, this is not unexpected - I think typicaly winch draw is somewhere around 200-300A, while the highest output OEM alternator might touch 120A. Therefore, you were winching off of your full alternator output, and the shortfall was being made up by the battery.

This would give you a GEN light. If you had an ammeter instead, you'd see it on the negative side of the scale for a little while.

Since your battery was rather drained by the pull, the alternator continued to run somewhere near full output for a while to charge the battery. This would have stopped once the battery was fully charged again.

The GEN light will NOT illuminate after the next KEY-ON cycle, provided the battery was good (which is apparently was.) The GEN light does not respond to "hard codes" like the MIL/CEL (Maintenance Indicator Lamp/Check Engine Lamp,) but you may have a "soft" DTC (Diagnostic Trouble Code) set in the PCM (Powertrain Control Module.) "Soft" codes can be reset with a reader, or will clear themselves after a predetermined number of engine start cycles (the engine is started and comes to operating temperature.) "Soft" codes do NOT illuminate the MIL/CEL.

So, nothing for you to worry about. I realise I could have just said that to begin with, but what would you have learned from that?:laugh:

5-90

Thanks a lot for your response 5-90 I really appreciate it.

Timber · Aug 31, 2006

I love this place; I learn so much here--both whys and hows.

My gen light came on winching

90Pioneer

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5-90

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90Pioneer

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Timber

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