decided to die...

I have had the van for 10 years now and never had this issue. I have taken off the negative cable several times and never blew the PCM...today - I did.

I was wondering if someone could help diagnose what the heck happened. So the voltage regulator - I am thinking - fried when I put the negative cable on after working on the van. I was doing an alternator...and here is how I got there...

I bought a reman from Rock Auto. It seemed OK. Looked good - no worries - I thought. Well, I installed it all the way and went to put the field coil? plug on and it would not stay on. The Chinesium connector did not have a lip for the connector to 'click' on to. So...I thought -- well let us take the back of the alternator off, get a new diode/connector (which I did) and replace it. It isnt hard to do at all. While I was in there I replaced the brushes too. Everything came out great. So I thought...

I put the alternator in and it worked great. It was putting out 13.3 at all speeds and 13 at idle. Not too bad...but... I should have just left it alone, but I got thinking that I didn't tighten down the power cable enough, so I decided to tighten it up. So I unlooked the negative battery cable, tightened the nut a 1/2 a turn (yea it was a little loose) and was thinking - great - Im done.

I went to put the negative cable on and the 'magic smoke' came out from the battery cable of all things...and I am being little sarcastic, but it was like that..As soon as I touched the cable to the battery, I hear a POP with a bright little spark and I though - ahhhh no---reallly??? FWIW Im an engineer, and I have seen that POP before, and it usually means something just fried...

and guess what - it was the voltage regulator in the PCM. I guess that is what had to happen. So now, I am getting no charge at all...it is running at 12.0...yea - screwed.

So I tried swapping out the alternator for another I have from long ago and it did the same thing - no charge...just 12.0...ffffffffffffffffffffffffffffffffffff]
Funny thing is that the van runs fine with no check engine light - hmmmmmmmm.....

questions:

• Is my diagnosis correct that the PCM voltage regulator took a crap
• Is the PCM user fixable? Im OK with sodder but dont understand why this happened...or how to fix it
• I have seen the rebuild services for about 120 bucks - are they OK? I am on my second PCM in my 10 years of ownership..I usually just did the swap thing - but has anyone tried those services?

Thanks all

 

Reconnecting the battery shouldn't cause issues, unless the ignition was on?? But yeah, sounds like bad voltage regulator. You can install an external regulator, Several threads about that here in the Dak, and Ram sections. (not an uncommon failure....)

 

The correct charging voltage for a 12v battery is 13.8 - 14.2 so yours was too low to begin with. Are you sure the pop you heard was from the PCM and not the alternator? When you tightened the power cable lug on the alternator is it possible the insulator cracked, causing a short to ground?

 

What year is this? The newer ones should have a fuse on the positive alternator lead in the pdc. Depending on the year the pop may have been the fuse.

 

Thanks - Ill look into that.

Well, I dont think so. I had a second known good alternator and it operation was the same thing. Nice to hear that the rebuilt one wasnt performing correctly. But, I can check the first alternator just to make sure. If I shorted it to ground, would the fuse that Morpatire talks about below may have burnt? Thanks for the thoughts

The pop I heard, well I couldnt tell you where it came from because there was a significant 'light up' of the negative post. It really caught my attention. What I mean is that there was a little, but very bright ball of light and a pop at the same time...I have never seen that behavior before.

It is a 2002 - Ill check the PDC...thanks -totally forgot about that --- that does make sense.

Thanks all for the thought - Im going to check it out in a few

 

That sounds like the battery received a dead short. Smaller wires would've burnt up quickly, so this had to be a battery cable to ground short somewhere.

 

I think you are right. The mount on the first alternator seems to have cracked.

The alternator fuse was blown. So I only could find a 120 today, but I replaced it and now van is running and charging.

I still have low voltage numbers though...13.1-3 and it gets below 13 with everything on. I think these alternators are tired. But - any other ideas?

thanks for all the help everyone.