kujo_jr

Hey guys. First, thanks for any help anyone can give me. i am down and out, and can't figure this stupid jeep out. I love my jeeps, I have 5, but this electrical problem is testing my faith with my 2000 xj. for about a month, i have been having this problem where i start my jeep, and the volt meter is only reading abt 12 v. then when i push the accellerator, the voltage drops all the way down, and the check gauges light comes on. it will still run perfect, for quite some time, like 5-6 hours, but then the lights start to dim and battery gets too low. also, sometimes, my speedo will jump up erracticly-like peg out to 100 even if i am only doing 10. i have also got code 1698-no message received from tcm- but it hasn't come in recently. checked the belt, i have had the alt checked 3 times, and put in 3 different optima batteries from my other jeeps. nothing. i cleaned up the battery cables, alt cables, and I think all of the grounds. nothing. it doesn't drain unless it is being driven. i went thru the wiring around the trans thinking maybe some thing was grounding out but i still can't find anything. i read that the voltage reg is in the computer not the alt, and was starting to think that may be it. it hurts my pride to ask for help, but maybe the gurus here can help. A Big Thanks Again Guys

fantic238

It could be the diode unit in the alternator, or some loose wire from alternator to regulator to battery. Check charge with an amperometer ON the battery, don't trust the gauges, ignore the speedometer.

kujo_jr

Fanatic, thanks for your help. I tested the voltage at the battery while running, and it was 12.4- which is about what the gauge was reading inside. I checked resistance in the wiring from the alt to the cpu and it was good also. I am not really sure how to check if the diode would be bad though. Is that the other connector on the alt? My meter has a diode check function, but i ve never had to use it. Thanks, again

fantic238

You need to compare the voltage measured at no charge, good charge, bad charge and report the values.

fantic238

I've had a look at the wiring diagrams, the regulator is in the alternator, activated by the ECU, it's the same piece of the diodes, actually the diodes are the voltage regulator itself.

kujo_jr

It was the gd alternator! after all that! I took it back to autozone where i got it to have it tested again for like the 8th time because i had nothing else. he tested it three times and passed every time again. i then convinced him to give me another new alt as mine was under warranty from there. bring it home and twenty min later, Perfect! thanks again fanatic. I really appreciate your help

BuckB91XJ

I have found that when autozone checks alternators and starters, their test bench isn't very accurate. I watched the guy run the bench and I don't see where it does a load test. I've had both a starter and alternator check good on their benchg and end up being bad. The guys at my Autozone in Oak harbor, Wa. are great. Even if a part checks good on their bench they will give you the option of getting another from them, everytime.