I've got a 2003 Excursion. Several months ago I noticed that the battery light would come on at idle, but would go out as rpms increased. I figured it was an alternator problem, and evebtually I had to jump start the truck. I took it to the shop and they replaced the alternator. After the new alternator was installed, I was towing a camper, roughly 8 - 9 thousand pounds, at highway speeds and the battery light came on again and stayed on for long time. The light would occassionally come on and go of while traveling at highway speeds even when I wasn't towing. I took it back to shop and they just replaced the recently installed alternator with another new alternator, assuming it was a faulty new alternator. Now with this new alternator, the light doesn't seem to come on as often, but still does occasionally come on. I noticed it frequently came on while towing heavy loads up grades, I tow with the overdrive off. However, there was another time when my wife was using it and not towing, and the light came on as she was just driving down the road and in a parking lot. I took it back to shop and they checked the battery's and alternator output and said they couldn't the battery light to come on and the battery's and alternator checked out to be fine. Does anyone habe any idea's what's causing this?

 

Your batts have a bad cell, the alternator is working had to try to charge the bad cell, and it is frying the voltage regulator in the alternator. These trucks also charge the camper batt when connected, so your little 110amp alternator is trying to "maintain" a charge in three batts, one of which has a bad cell.

For the shop to test the batts they must be completley disconnected from the batt cables, and a load test performed. Most shops dont realize this and just hook up to the batt while it is still in paralell with the other batt and test it giving a false positive reading.

Been there done this, got a 220amp alternator to prove it.

 

Thanks for the reply,...I will contact the shop again and ask them if they can remember if they tested the batteries disconnected, and mention to them what you explained. Is there anything else I need to be concerned about, if i figure out which battery it is, will I be okay to just get a new battery, or do I need to be concerned about any other parts, I have a lifetime warranty on the alternator. Thanks again.

 

Always replace the batteries in pairs. The bad battery will drag down the good one.

 

yep. i replace my batteries 2 weeks ago, and BAM the battery light came on yesterday. Just replace the alternator today.

Always replace batteries in pairs and get a NEW alternator, not reman, when it needs to be replaced. This 104* heat everyday has been taking its toll.

 

Good, BTW, battery light coming on mean alternator failure 9 times out of 10, not battery failure.
The alt fails because the batteries were over working your alternator which is why I recommend, if you can afford it replace the alt and batteries at the same time, then take a breath of air and forget about needing to play with those parts for quite some time, at least 3 years, minimum.

 

I called the shop, and they assurred me that they were aware they needed to check the batteries while they were disconneted, and that is in fact what they did. They said that everything, batteries and alternator, checked out ok. They said they ran the truck for some time to try to get the light to come on but they couldn't duplicate the condition to troubleshoot it. Not much of an answer.

I talked with a guy at work today who is sort of a gearhead, and he explained the following to me.

Sounded to him that my alternator was not able to keep up with the draw from the truck. My truck has two DVD monitors, on the back of each front seat headrest. Both monitors were on because my kids were watching their DVD, we had the stereo on, and also had the AC on since it was a very hot day. On top of that we were towing our camper, which the alternator was also trying to maintain the charge on the camper battery and whatever draw there was comming from the camper.

I explained how the light would more readily come on after I had towed the camper up a long steep grade, which really worked the engine hard, but the light would usually come on after I had cleared the hill and the engine wasnt working hard. He felt that was because as the engine was working hard to pull up the grade, the fins on the alternator were spinning fast due to the high rpms, thus helping cool the alternator, but as I cleared the hill and the engine wasn't working hard, the rpms dropped, thus the fins weren't spinning as fast and not cooling the alternator as good. He said excessive heat will cause an alternator to fail.

He suggested that I upgrade the alternator to one that has more output and that should take care of the problem. It all made sense to me as I was listening to it,....what do you think?

 

sounds like you need to do some alternator shopping.............

 

You also have to remember that heat means added resistance in the copper lines in the alternator meaning the alternator isn't producing as much current as it would when it's cooled down and with all that equipment running and the extra heat being produced from the AC radiator and motor, yea, I'd have to say it's time to replace the alternator and upgrade to a 200 or 220.
Basically your alternator is on the verge of electrical failure

 

OK, I called NAPA and they said they only show a 110 amp alternator,...so does anyone have any suggestions on where to get this upgraded alternator.

 

Here ya go http://store.alternatorparts.com/199...okediesel.aspx

If I remember correctly that web site was referenced on another post on this forum.

 

I had the same problem after getting the Alternator wet when I washed the engine and didn't let it dry long enough. Tested everything and all was ok. Light continued to flicker at times at idle and speed but all seems ok now. Bats are like new and test well under load. I would take an uneducated guess that there was some corrosion on a diode connector. If it happens again I will opt for a high output alternator and bite the $225.00 as the last thing I want is to get stranded at 35 below!

 

Where did you get that monster at???????????

 

http://www.db-starter-alternator.com...8-03%20%207796

I got the chrome version, but you can also get the regular casing. Make sure you get the upgraded wiring kit too.

Heres a pic

 

Thanks Brandon appreciate it