Topic: Help! 97 TJ 2.5 Electrical Disaster!

[Woodyhfd]

I've been working on a 97 Wrangler SE 2.5 that I picked up recently. I was taking it on a short test drive today when the "Check Gauges" light went on after about two miles. The Voltmeter was off the high end of the scale. I drove another half mile home and turned it off. Now, when I turn the key, I get absolutely nothing, no lights no beeps, etc. Needless to say, it won't start either.

I've started to check the fuses and fusible links and so far they seem okay. I'm wondering if I fried the computer. I welded up a crack near the catalytic converter last week. I disconnected the battery but not the alternator at the time. However, I started the Jeep a few times since and drove it for a couple of miles.

Any suggestions?

Could there be a fuse or a fusible link that I'm overlooking?

[yellowta]

Not sure about the tj, but most vehicles will have a big fuse for the alt. around 100amps. Sounds like you may have fried the voltage regulator inside the alternator though. Could have messed up the computer, but the problem is most likely in the wiring somewhere.  The dash and ignition would still work even with the cpu completely disconnected. It just wouldn't start :?

[Woodyhfd]

Okay, Here's an update:

I removed the battery and alternator. I placed the battery on slow charge all day and had the alternator tested. It was fine. I removed all of the heavy cables and cleaned the terminals. I only found one fusible link and it was still good.

I decided to put it all back together and haul it to the dealer. Then, just for kicks, I turned the key and it fired right up.

The TJ has maxi fuses which, according to the owner's manual "replace all inline fusible links previously used". (No mention of this in the Haynes Manual). It also has an "Auto Shutdown Relay" which I guess is a circuit breaker (also not mentioned in the Haynes book).

I'm guessing that my cheap battery had gotten run down as the Jeep had been sitting for a while while I replaced a transfer case. The fusible link that I found must have been a used item from an older Jeep that was installed when the previous owner replaced the fender to which it was attached. It is now redundant due to the maxi fuses.

I think that the alternator overworked itself trying to recharge a run down battery through cheap, corroded replacement cables.

The Auto Shutdown Relay must have reset itself after it cooled down.

My next step is a better battery, some quality heavy duty battery cables and a real shop manual.

Thanks for all of your help.

[yellowta]

Good to hear you got it running   A friend of mine had his jeep die on the trail once, same symptoms except for the voltage thing. Turn the key, abslotutely nothing. Turned out he didnt' put the battery hold down back on when he installed an optima, and it bounced high enough to rip the power lead out of the breaker/fuse box.  :shock:

[aw12345]

The auto shutdown relais powers the ignition and the fuel pump is a chrysler thing. Is a great place to wire an alarm system into.

Art

[Enjoi]

mine did exactly the same thing, it was corroded battery clamps and cables. changed them up and walla good as new

[98Ss1LWEE]

i SAW THIS ADN IT RELATEDS TO MY POST, LET'S see if I can revive it for som help, I will clan terminals and cable tomorrow, and chec voltage out of alternator, but m gauge reads high for a few seconds, then check gauges ligt comes on adn gauge spikes. Now gauges not working intermittenlty, all guages that is.  Checked voltage at battery and getting 18-20v. NOT GOOD!  Check connectinos under fuse box, at battery, to PCM, etc... Can't figure this one out!

[sharpxmen]

i SAW THIS ADN IT RELATEDS TO MY POST, LET'S see if I can revive it for som help, I will clan terminals and cable tomorrow, and chec voltage out of alternator, but m gauge reads high for a few seconds, then check gauges ligt comes on adn gauge spikes. Now gauges not working intermittenlty, all guages that is.  Checked voltage at battery and getting 18-20v. NOT GOOD!  Check connectinos under fuse box, at battery, to PCM, etc... Can't figure this one out!

how about telling us what Jeep you have, is it same year and model as the title?

If yes and you get 20v then something's wrong with the voltage regulator (which in this case is integrated in the PCM)

[aw12345]

Anything over 17.5 volts will nuke an ecm in short order, if it's a TJ check the connectors for the instrument cluster, provided it runs and drives good. The cluster is bus driven and is known to wig out, there are several service bulletins and factory fixes

[98Ss1LWEE]

Yes, 97 2.5 TJ.  Yes, over 18 volts to the battery and essentially the ECM.  Ok, so what can I do about this?  My ECM is part number 56041-305AD.  Will a 305AC work? What's the specifics? Does anyone rebuild? Does it have to go to dealer before it will run if i swap it?  Nothing else is a problem that i am aware of, so really? ECM Bad?  Once i noticed overcahrgin i shut it down, adn it was intermittent at first, now jsut straight overcharging!  WEll, if ECM fried, is that what caused it, or jsut a result? Coudl the alternator be bad and overproducing, or jsut eCM that regulates?   Thanks guys, this is bugging ther crap out of me, and I really need my Green Machine back on the Snow and ROAD