99 XJ batt gage drops between 11-12 at idle, normal?

so last 2 days I notice original factory radio cutting on/off, speaker and display both cut off for a few instants like a loose ground or power wire. I have noticed this after 10 min or so with fully warmed up car this happens sitting at a traffic light. 2nd time it happened was yesterday, & I for the first time noticed the batt gage which always is straight up at the 14 mark, now is in between 9-14 so I'd say 11-12v. If I rev up the engine it recovers to 14 and holds the rest of the time on a local drive at idle or driving holds 14.

so is this normal ?, maybe I never noticed.
should the batt gage simply stay at 14 all the time?
maybe radio is going out but thats it?

possible alternator replacement is on my radar ?

check and clean battery terminals. (take them off and clean the contact surface)

IF that doesn't fix it, yeah, probably alternator swap time.

Do your lights and other accessories dim? Have you used a DVOM to confirm battery voltage, both running and not?

Johnnie Walker said:

Do your lights and other accessories dim? Have you used a DVOM to confirm battery voltage, both running and not?

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the first time I experienced it I had the radio on and blower on. the radio lights were blinking on and off and I thought the blower speed slowed but I am not 100% on the blower, wasn't paying close attention. I have had this car going on 2 months and its really unmolested, little has been does aside from routine maintenance, upgraded shocks and several exhaust parts replaced from what I see.
so ..no belt slipping, it has done it while driving 3 times, 1 time every day last 3 days. just checked cold, its 12 degrees here. completely cold 12.2v battery voltage engine off 14.0 - 14.2 at idle. but gage at 14. I am yet to catch it but I'll carry a DVOM on pass seat and maybe if it does it again I can test it quick. My first thought was alternator but don't really know the XJs that well yet.

Sounds like alternator, but only your multimeter will know for sure.

Grounds, battery cables, or alternator brushes. The alternator brushes can be replaced separately if you can find a source for them. You can take off the back cover and remove the brush assembly to see how much they are worn down. If knocking the alternator with a steel pipe or hammer brings the volts up, its surely the alternator.

grounds and batt cables exc condition, intermittent so diagnosis is difficult. I got a Denso alternator on the way from rock auto and will swap next weekend. I'd rather start here and throw the part at it for about the same cost of a tow if I were to ignore the issue. will post the "after" results.

Go to your local parts store and pick up some replacement battery cables to freshen it all up too. Or contact 5-90 to get a nice set of cables.