Pigeon

98 XJ 4.0 4X4 AW4, Sunroof (woohoo!)

Never had any charging issues till recently. Vehicle starts, drives, and runs good. It normally runs right at 14 volts according to the dash gauge. When I turn the climate control to any selection that uses A/C (including defroster), the charging gauge begins to drop. It will drop slowly at first, taking about 20 seconds to drop to about 11 volts. It will then fall to 9 volts (the lowest reading) and the 'check gauges' light comes on. If I turn the A/C off, the gauge returns to normal.

I don't use the A/C because of an issue with the blend door which I have yet to repair. This problem only surfaced when I used the defroster. I haven't done any diagnostic work on the charging issue, or even checked it with a meter when it occurs. I know that when I was charging the A/C last week, when the electric fan came on it had a slight squeal. I don't know if the charging issue was present at that time.

Could the fan or the compressor clutch be drawing an excessive amount of electric? Enough to drop the gauge to nothing?

freegdr

First thing id do is have alternator and battery load tested most place will do this for free nowadays. What was squealing ?

Pigeon

It was coming from the electric fan.

mlepesant

Have you tried tightening up your serpentine belt? The squealing and the symptoms you are describing could come from there.

Sparkys92XJ

If your belt is loose and you turn your ac on the compressor kicks in and could be causing your belt to slip. Therefore possibly allowing your alternator not to charge correctly.

Pigeon

I should have some time to work on it today. The belt needs replaced, so I will replace and adjust it. After I eliminate belt slip, if I'm still having the issue, I'll do a load test on the battery and alternator.

karl4x4

I spent some time in the past on weird electrical issues.
One common theme is dirty battery connectors.
They sometime look clean but have a "glaze" over then that doesn't allow full current flow.

Spin your electric fan by hand. It should turn freely. If it does, good chances its not your problem.

If you suspect a system to cause an excessive draw or drain, pull the particular system's fuse and see if the voltage still goes down.

Also, check the voltage with a voltmeter between battery terminal and cable (pos to pos and neg to neg). If you have any voltage that means you have a bad connection.
Good luck

freegdr

Belt slipping...Theres you sign ...