Topic: '97 Wrangler - not charging - help pls

[Crunch]

So, last night out at the beach, the Jeep stopped charging the battery. There was nothing obviously wrong to fix on the spot, but managed to limp back home on just the battery (it was close, but made it,, 45 miles with headlights)

So, this morning I start going through the steps. I figured it must be something with my new alternator...nope...replaced it and no difference.

Here's the symptons:
-No Charge from Alternator (none, and no question about it)
-I'm measuring no Voltage across the field terminals, or from either field terminal to ground. I'm pretty certain there has to be voltage here.
-I see Battery power at the Alternator charge connector
-I see ground at the Alternator ground connector.

Here's what I've done so far:
-Replaced the Alternator - no help (lifetime warranties are grand)
-Checked the Battery Temperature Sensor - checked out fine.
-Checked the field terminal continuity to the appropriate pins on the PCM, checked out fine.
-Checked the Battery, and cleaned up the connection - no help
-Checked the PCM power inputs that are relative to that circuit, all checked out fine.
-Checked the relavent fuses (one under the dash, and one under the hood) - checked out fine.
-Checked the relay for the Automatic Shutoff (ASD), relay is fine, and all inputs/outputs check out.
-Checked the fusible link from the power distribution box, it's fine.
-There are no PCM error codes.
(I'm using the Factory Service Manual btw)


Everything seems to be pointing to the PCM, but I'm PRAYING that someone will know something I don't, something really simple and cheap  Any ideas?

Also, does anyone have any information on PCM's, models, etc.. I need to know what to look for. Like differences/similarities between years, if they are engine specific, etc.. I can post my part number if it helps. I've been trying to search the net for such info, but I haven't found anything so far.

Of course the Jeep Service/Parts were closed today, so now I'm stuck.

Any help and/or advise would be great.

Later,

[SMC4WD]

I have a 95 YJ and I had a charging issue...  I beat my head up against the wall, chased my tail and threw all sorts of money at it.

I don't know about a TJ but, inside the engine compartment there are a few fuses... I blew both 50A fuses...  How?  I dunno, but I did.  Replaced them and all was fine.

I hope your problem is that simple.

[jagular7]

Have you checked the output of the alternator? Remove the charging cable from the alternator, disconnect the battery and check its resistance. I don't know if the 97 TJ has one or not, but there is usually a fuse link to the battery from the alternator. The link will blow. If you want, pinch the pin lead to the multimeter in front of the link and make sure the line is good from the alternator end to the link. Then after.

[Crunch]

A friend who is a mechanic helped me diagnose the charging system over the phone this morning. Turns out, the PCM is indeed bad as it is not turning on the alternator with voltage from the PCM to the Field Terminals on the alternator. I was however able to jump the Voltage Regulator Circuit from the PCM to 12V (battery), and turn the alternator on, so it's running and charging now.

Now to try and find a PCM cheaper than the $460 the dealer wants for one. :)

Thanks for the replies.

[Guardian7]

Makes me glad I have an 89 YJ without all the PCM involvement to complicate things just a basic delco alternator.