Overcharge indicator

2001 4wd AW4 Limited: my check gauge lit up again today (sporadic for the past week) where the voltage gauge indicated 19 volts-obviously not good. Earlier in the week, I disconnected my dual battery setup thinking it might be causing the problem but it wasn't. Wondering if it could be the alternator or the regulator in the PCM. Is this a common problem with the alternator? I don't have a voltmeter, planing on borrowing one from my neighbour when he returns next week. Just wanted to know what I should do (want to avoid the dealership as much as possible). If its a new alternator I need, simple enough or do I need to have the alternator and regular checked at the same time.Thanks.

I believe the regulator for the 2001 XJs is part of the PCM, not built into the alternator like on the older models with the Delco alternators. If your alternator is putting out 19 volts, you don't have an alternator problem you have a regulator problem.

Step one would be to put a multimeter on the battery with the engine running to see if you're really getting 19 volts of if you just have a flaky gauge. Should read a bit over 14 volts at idle with no accessories on, maybe 13 to 13-1/2 volts with headlights and a/c running.

The PCM really acts funny with respect to the charging system. If it reaches 15 volts during charging it will trip the check gauge light and the gauge will go to 19 volts. Does the same thing if the volts gets to low also.

It shouldn't be an alternator thing because the PCM runs all the regulating. What batteries are you running in the dual setup? Just make sure they are the same. Is this still a stock alternator? Do you have a on board welder?

hinkley

Dunno if it has any bearing on this problem, but remember that the new XJs have a battery temperature sensor under the battery. Have you modified anything that would make this inoperable or give a false reading from it?

I am running two optima red tops (installed them at the same time), my alternator is still stock (rated at about 120 amps), no welder. The battery tray was not removed or altered at all. The check gauge/voltage spike to 19 volts happens randomly but mostly when I hit over 60mph. Thanks Mark and Eagle for the replies.