Voltage and Check Gauges light

I did a search but didn't really find this. On my way to work the check gauges light came on and i noticed my voltage meter was pegged at 0. The truck was running fine so I drove it in. Once at work, I turned it off, turned it back on and the light had cleared. At lunch ook it for a quick spin and after a mile or so the light came back on and the voltage meter cut out again. Once again I turned it off and on and it was fine (voltage around 14, but a little low). I'll be going by Autozone after work, but anyone got any ideas?

Thanks
S

Yah.
It sounds like you have a OBDII equiped Jeep with a PCm controled guage cluster.
Since the PCM control both the CEL and guage function, it is telling you that you have a problem, the CEL, and what it is, zero on the voltage guage. Your alternator is likely bad. Other alternatives are wiring, or even, since it also controls field voltage, the PCM.

Ron

My guess is the alternator since it's the stock with 173,000 miles on it and I replaced the battery this summer. How hard is an alternator replacement on a 99? I've done a bunch of work on the XJ (water pump 3 times, head gasket, etc) and I've replaced alts in the past on other vehicles, but what's involved in relaplacing it?

S

Not bad. Loosen the belt. Tensioner bolt is on the left side, some of the bolts are hidden.
Remove belt.
Remove battery so it's not in your way.
IIRC I had to also remove the fan because the top bolt would not clear it.
Remove the harness from the alternator and remove the mounting bolts.
You will do some of the wrenching from the bottom.

Reverse whatever proceedure you used to remove it.

Make sure no children are present when you perform the proceedure as you will use many "Fit It" words and may even discuss with your buddies, the engineers family tree and how dogs may be in it

I did one in the field, in in a down pour, and it took me about an hour.

Ron

Thanks for the help, funny enough, I had to replace one in a downpour in a Pepboys parking lot on a mustang like 15 years ago.......it sucked, but at least the alt was on top.

Is removal to the top or to the bottom, the haynes manual gives very little useful info on the removal procedure and simply says to unbolt it......I had guessed that much, and I've never taken the mechanical fan off, is removal similar to removing the pulley on a water pump?

S

Easier to drop it out the bottom. Same with install.

Yah, 4 bolts. You have to unbolt the fan shroud, and unbolt the fan, then pull both of them almost as an assembly. Wear mechanics gloves if possible.

Ron

BTW, after reading some more similar threads, I'm pretty sure what I'm going to be replacing on my XJ tomorrow. I've had squelling (even with proper tension and a new belt)and electrical gremlins (radio cut out and wouldn't turn on a couple of times, doors sporadically unlocked when I started the truck, and a couple of other odd things) for about the past 6 months or so.....

S

Zuki-Ron said:

Easier to drop it out the bottom. Same with install.

Yah, 4 bolts. You have to unbolt the fan shroud, and unbolt the fan, then pull both of them almost as an assembly. Wear mechanics gloves if possible.

Ron

Click to expand...

Broke the top off of the fan shroud this summer.....saves some unbolting :sad1: :twak:

Thanks again,
S

Correct me if I'm wrong guys, but the alt wouldn't cause zero volts. I would look at a loose connection at the cluster itself, especially where everything else operates while you have zero volts. If you actually had zero, it wouldn't run+no lights. Even if the alt isn't spinning, the volt should still indicate battery voltage (obviously above zero, unless the batts dead)

I know it's hard to understand.

The thing which fudges up your logic is that the meter is not a direct read. It is not a meter across the battery leads. What it is, is an output from the computer, telling you what the voltage is; just like the speedo on these units is just an output from the computer and not a physical connection to the transmission. If you loose communication with the cluster, you loose every guage; a neat little trick which there is a TSB on.

Somebody at the factory decided to "help" us a bit by giving us a CEL and a dead Voltmeter output. In otherwords, it's a idiot guage.

Ron