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Intermitent voltage loss, '98 XJ Limited

bjoehandley

NAXJA Forum User
Now that we have most of the major issues taken care of on my XJ, outside of rust, an intermitant voltage loss issue had popped up. At this point, here is what we have as knowns;
So far as I know, the alternator is factory (was in the truck when I bought it in '03)
My Father doublechecked the belt and has it as tight as he feels is safe (this is the fourth and last standing XJ in this family)

It runs well enough, even though we haven't done the tune up yet, and it starts almost right away

Lights work (barely for the headlights, but those are 14 y/o and the reflectors inside them are shot)

There is an issue with the foglights not working (at this point, new ones or jst removing the old ones would be best) and the clockspring is shot.

Only 1 speaker left working, one might be a plug or soldering issue with the aftermarket door speakers, the other two are dead OEM speakers in the roof.

The rear wiper motor is shot, maybe the windshield solvent sprayer motor too.

I have the new Mopar relay for the aux fan, but not installed it yet, not really had thebtruck hot enough to need it between the better radiator and it being winter in the Midwest, Chicago Suburbs to be exact....
 
Describe the loss of voltage symptoms observed, and the alternator and/or wiring diagnostics you have performed so far.
 
Well, it goes from getting close to, if not full voltage to nothing, last couple times it's been when we drove it at night, so it had the added load of the lights being on. Haven't had the time or weather to look further yet, although I did buy a can of belt conditioner since that is the only cooling system related part we didn't replace beyond thermostat housing and engine driven fan and shroud when that work was completed recently and has been on it a long time now (probably should have bought one of those too). Haven't pulled the alternator to have it tested yet and I'm concerned that since the truck has sat around a lot, especially when Mom has been on Death's door for parts of 2015 and 2017, that the alternator could be seized.
 
If the alternator was seized, it would simply not turn, and the belt would scream and start smoking.

If the dashboard gauge shows 9 volts there is an alternator issue, usually worn brushes. If the dashboard gauge shows 19 volts there are connectivity issues, usually loose/dirty/corroded wires and/or wire connections.

Load test the alternator and the battery. Clean and inspect all the connections, grounds, and wire condition.
 
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Usually the voltage runs about right, 13+ volts and doesn't go over. Now when started then using the lights right away (at night), the gauge reads around 9 volts then drops to 0, but the truck seems to drive well enough (other issues not included) otherwise.
 
Ok, new info, took it to the local Subway to get lunch and the voltage gauge started out half way and eventually went to 14-15 volts, but started to misfire again when I turned the blower fan on high.
 
The dashboard gauge should show 13.8-14.4 volts at all times. Anything higher or lower is a problem.

9 volts and misfires point to low voltage. The alternator is the likely source, but continuing to drive with a faulty alternator can cause battery failure.
 
Thanks Tim, been talking with Dad on this since he has spent a lot of time maintaining the other 3 XJ's we had and has been doing most of the work on this while I've been in the house with Mom in case she needs anything for this work. He wants tpo throw the battery on a charger and give it a good charge since we can't seem to keep it running reliability long enough to do that on it's own, plus do a tune up now that the parts to do so are here since last tune up was about 10 years ago to try and eliminate that as well as lack of charge as a possibility before digging into the alternator. If need be on the alternator, I know of a shop that can actually rebuild them and would prefer that over a reman, even if I have to add an other week to the time it would be out of commission......not like it's my regular transportation any more.
 
Measure the voltage at the battery when you're putting the fan on high. If the battery voltage isn't sagging badly, then you might need to look at things like the ignition switch and ground points for poor contact.
 
We had it running well enough that I could drive it to work yesterday, Dad threw a new #1 plug in it with the rest of the Accel tune up kit, dressed the belt, and picked up a new belt while I had it at work, but the brakes failed on my way home........I swear that the below has become a norm with this truck..................:dunno::gee:

ztw3g.jpg
 
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