Voltmeter Gauge Pegged ('94 XJ)

R_Willis · Nov 15, 2004

I just bought a 1994 Jeep Cherokee Sport 4x4 to use as a bad weather (winter) vehicle and for some daily driving. The thing has 129k miles on it and seems to run pretty darn good, came from a used car lot. I went through and have done a lot of the "regular" stuff including oil change, tranny fluid change, tranny filter, oil filter, air filter, PVC lines from the manifold, plugs, oil pressure sensor (broke it), antifreeze, and a fuel filter.

Problem I'm having is the volt guage is constantly pegged. Seems like she starts up fine however. The battery terminals were pretty nasty and corroded, cleaned them up.

So, sound like a battery that has had it? an alternator? any other ideas? I have no clue how old either is.

How hard is the alternator change on these anyway, maybe I should do it either way as some more preventive maintenence.

Any help would be greatly appreciated.

R_Willis
1994 JEEP Cherokee Sport 4x4, Red, 129k

Matthew Currie · Nov 15, 2004

Before doing anything else, you should get a proper voltmeter and measure the voltage at the battery terminals. If it's around 14 volts when running, you're fine no matter what the gauge says. The XJ voltmeter is calibrated with a magnet that is glued to the inside of its case, and if the glue bond breaks, it will go crazy.

The voltage regulator in your XJ is built into the engine computer, not the alternator, so a voltage that is actually too high will not be cured by alternator replacement. Of course, if the gauge is pegged when the engine is off, it's guaranteed not to be an alternator problem anyway.

These days you can get a workable digital multimeter at hardware stores and elsewhere for under ten bucks, and a pretty decent one for 25 or less - far cheaper than paying to fix things that may not need it. I would not replace an alternator as a prophylactic measure, because they can go for well over 200 thousand miles without trouble.

90Pioneer · Nov 15, 2004

$3.00 digital multimeter at Harbor Frieght. Works great!

highhilleer · Nov 15, 2004

prophylactic measure[/QUOTE said:
Now I'm going to have to find a dictionary. My mechanic doesn't use this kind of language. He says things like "if it ain't broke, don't fix it".

Eagle · Nov 15, 2004

90Pioneer said:
$3.00 digital multimeter at Harbor Frieght. Works great!

Ditto.

Bought a couple to carry around in mobile tool boxes.

But you have to be careful with Horrible Freight Salvage. They'll have the exact same item selling for as many as four different prices depending on which catalog you look at, and often the same item in two places in one catalñog at different prices. And the super bargain prices never seem to show up on thier web site.

R_Willis · Dec 14, 2004

Ok, update radio and the sunroof/moonroof controls died the other day. Haven't checked the fuse yet, as my fusebox cover under the dash by the pedals is missing the cover and I'm not sure which one I need. Anyone have the # of the radio/sunroof controls (they appear to all be numbered)?

Anyway, my volt guage still goes to ~15 with the key turned to accessory and once the engine is fired it hops to 19.

Just replaced the alternator and the battery with new ones as good winter preventative maint anyway...

Still does it....

Guage problem? Regulator that is built into the PCM/engine gone bad?

Bet that internal regulator isn't a cheap fix..

I'm going to grab a voltmeter while I'm out today and check the current across the terminals? What mode does it need to be in to do this?

Any suggestions....

Matthew Currie · Dec 14, 2004

You really MUST check the voltage at the battery. The gauge on the cluster is a poor design, not to be trusted. The voltmeter shares wiring with other accessories, and often give false low readings. In addition, at least in the version you have (91-96) the voltmeter calibration is done by a little magnet that is glued to the inside of its case. If the glue dries and cracks (which it does occasionally) vibration will put the meter way out of whack. Once you have a voltmeter, if you care to bother, you will be able to recalibrate it and reglue the magnet. A thick flexible glue like Shoe Goo or 3M emblem adhesive works well ( you need to move the magnet around, so it must be soft and have some setup time).

Although it's possible that the built in regulator has gone bad, the PCM monitors voltage, and it should throw a code.

The voltmeter should be set to DC volts. Across the terminals, it should read approximately 12.6 with the engine off, and approximately 14 running.

R_Willis · Dec 14, 2004

Got myself a Clarke digital voltmeter.

Just got done checking...

Running 14.5 - 14.6 volts (at startup and checked it again after 5min of idling)

Not running 12.4 volts

I have never witnessed a code or SES or check engine (not sure what type of light these things throw) as of yet.

So, where does this put us now.

Thanks!

Digger87xj · Dec 14, 2004

R_Willis said:
Got myself a Clarke digital voltmeter.

Just got done checking...

Running 14.5 - 14.6 volts (at startup and checked it again after 5min of idling)

Not running 12.4 volts

I have never witnessed a code or SES or check engine (not sure what type of light these things throw) as of yet.

So, where does this put us now.

Thanks!

the guage is bad

yardape · Dec 15, 2004

I'm really interested tosee where this thread goes. My '94 XJ doesn't have voltmeter problems and runs like a top but will blowout cell phones and chargers within seconds of plugging them into the cigarrette lighter. My solution has been to avoid the whole issue by carrying spare cell phone batteries.

Matthew Currie · Dec 15, 2004

yardape said:
I'm really interested tosee where this thread goes. My '94 XJ doesn't have voltmeter problems and runs like a top but will blowout cell phones and chargers within seconds of plugging them into the cigarrette lighter. My solution has been to avoid the whole issue by carrying spare cell phone batteries.

Have you tried putting a voltmeter to the cigarette lighter? I don't know why it would be different, but it might tell you something. Remember too that the cigarette lighter is likely on a common circuit with the radio and maybe some other accessories, so you need to make sure a poor ground on some other circuit isn't pulling current through an accessory that's plugged into it. If you have an aftermarket radio that puts out a good deal of power, it would probably benefit from an additional ground line anyway.

R_Willis · Dec 15, 2004

..interesting...

As my radio and sunroof controls are no longer working as of a few days ago. I wonder what could have caused them to stop working...

Anyone know what number the fuse is under the dash? my cover the the diagram is missing, it appears they are all numbered...

So Matthew, think my guage is just messed up on that voltmeter?

Matthew Currie · Dec 15, 2004

R_Willis said:
..interesting...

As my radio and sunroof controls are no longer working as of a few days ago. I wonder what could have caused them to stop working...

Anyone know what number the fuse is under the dash? my cover the the diagram is missing, it appears they are all numbered...

So Matthew, think my guage is just messed up on that voltmeter?

Yes, I suspect your gauge is just messed up, but wouldn't completely rule out possible ground problems, especially if other things aren't working. There's a possibility that if some ground is bad, an accessory might be trying to ground itself through the voltmeter instead, turning it into an overloaded ammeter.

Anyway, your readings from the battery are right on the money, so I don't think you have to worry about your alternator and regulator.

Try fuse 2 in the under-dash fuse block (15 amp) for the radio, lighter and radio illumination. That's what it is in a 95. I have no idea where the sunroof might be connected. Nothing in the 95 FSM about that. If it's an aftermarket job, someone might have spliced it into that circuit.

R_Willis · Dec 16, 2004

Thanks. I'll give it a try.

All the sunroof controls are ASC labeled. Not sure if a sun/moonroof was even available as a factory option?

Voltmeter Gauge Pegged ('94 XJ)

R_Willis

NAXJA Forum User

Matthew Currie

NAXJA Member #760

90Pioneer

NAXJA Forum User

highhilleer

NAXJA Forum User

Eagle

Lifetime NAXJA Member

R_Willis

NAXJA Forum User

Matthew Currie

NAXJA Member #760

R_Willis

NAXJA Forum User

Digger87xj

NAXJA Forum User

yardape

NAXJA Member #272

Matthew Currie

NAXJA Member #760

R_Willis

NAXJA Forum User

Matthew Currie

NAXJA Member #760

R_Willis

NAXJA Forum User

Similar threads