jon-d

presumably I have a stock alternator and while winching along with my electric fan the alternator gauge drops to zero for a period of time even after the electrical load(s) are no longer there. Its a moment of puckering and staring at the gauge in hopes it returns to a normal charge rate while out in the middle of no-where.


Is there a reason why this happens? I would expect the alternator to continue charging even though the draw exceeds its capability. my fear is one day it will not return to charging the battery making the trek back to civilization a real pain.

dave1123

The only thing I can say is the PCM controls the charge rate and I can see it shutting down the alternator if it gets too hot. What amp rating is it? With a winch, you'll need about the biggest one you can find. The battery has a temp sensor underneath it and if the battery gets too hot, the PCM will reduce the charge rate as well. I suspect this is your problem because it seems as soon as everything cools down, the alternator comes back on line, right?

jon-d

I was thinking it might be a battery temp thing as well but it starts charging again approximately 30 to 45 seconds after the winch is turned off. I would think that if the battery is hot then it would take longer than that to cool. Also, the winch can run 30-60 seconds before it will cut out. its like it tries to keep up then at a point it just decides it cannot and cuts out completely. you think the PCM assumes there is a short and cuts it off to save the electronics?

dave1123

It's just supposition on my part, but that seems logical. The alternator would cool quicker than the battery. It's aluminum and in the airstream from the fan.

jon-d

So there is a temp sensor on the alternator? if that is the case then a higher output alternator should continue to run for a longer period.

jon-d

i went back and found my build sheet, from the factory it came with a 117 output alternator. but any of the dozen or so previous owners may have changed it to something else so who knows.

dave1123

Okay, as a point of reference, my 2000 cheap Laredo came with a 136 amp alternator, supposedly because it has a rear window defroster. I know they are available with up to 270 amps output, but at a price! They go for around $600. You should be able to find something in between.

That 270 one I looked at produces 117 amps at idle!

jon-d

thanks Dave. I saw a 250 amp alternator on ebay for under $200, is there another place that sells them or would i be better off sending out the one i have to be rewound?

dave1123

If the Denso alts are like the Delco ones, the output is controlled by the size of the stator windings. I know from experience larger windings won't fit in some cases. Also on some Delco alts, there is a difference in the brush holders. Me thinks you'd be better off just buying a larger one.

Fred/N0AZZ

On my XJ I installed a Durango one that I had rewound at a rebuild shop for a total of 160 amps (really only 149) that works well with my winch and a HD battery.