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MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

 
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Old 28 Dec 2012, 07:37 pm
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Exclamation MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

I brought Cruiser to get fixed, and since I don't know when (perhaps when someone previously replaced the alt or remote starter, both of which I had done) there has been a wire directly from the alternator to the PCM. When it is connected, all works (the PCM is now shot, btw, but getting fixed) and I'm wondering how an alternator can be diagnosed as "BAD" when it clearly works when it is "Frankensteined" with this wire. Without the wire, the battery drains and it dies within minutes.

Just wondering why I NEED a new alternator when clearly the pcm is bad, and replacing this might make the problem alright, when the alternator is properly ground?
And they tell me "The pcm has nothing to do with the alternator working"
me, "Ok, well then why cant you just replace the PCM and see how the alternator works after since it's a separate service?"
Them, "Oh no, if the bad alternator makes the PCM burn out, then what will YOU DOOO?"
me, "I'll deal with it, and replace the alt after if it needs it."
Them, "We won't do that. We can't install a new part with an old alternator"... HUH? I thought they weren't RELATED??? The dealership is denying to change the PCM without me allowing them to replace the alternator. Is this legal?

I really wish I were a mechanic! Thanks for any advice, I might still be able to change what they "fix" tomorrow since they have to wait for parts anyways. Best!

I hate to give too many details about my car for fear big brother is tapping me, so hopefully this can be generically calculated.

PS: 2005, Turbo, PCM is still warrantied So, I had to remove this wire to get the new PCM (this wire thing is not my fault and i shouldn't have to suffer for it) HENCE of course car won't stay charged (without my little secret whatever-the-hell-happened-wire) SO thats how I know this alt has been working...
Like I said, everything runs and stays charged indefinitely with the wire (Battery light is on, but this wire has been there a good year from my calc's before the battery light came on in end of Aug). Car was off the road from Feb 2011 to May 2012, and wire had to have been put on before that.

Thanks!
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Old 28 Dec 2012, 09:46 pm
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Default Re: MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

There's a lot of detail;
PCM's bad, caused by alternator
Alternator must be replaced because it causes PCM to fail

Someone has made a 'jumper' from alternator to PCM, this jumper makes alternator function

Alternators have two parts:
That 'generate'

and

That rectify

It sounds like there's no issue with it generating, it could be that they diodes in rectifier are fried; you can literally see them missing in some cases!

The PCM
'Regulates'

If alternator (output) isn't properly regulated, it 'full fields'. The headlights will get brighter, heater fan will spin faster, and if driven at freeway speeds for distance the battery can boil over and actually explode.

You can artificially 'full field' an alternator to test it.

On the Neon modified to run without a PCM, we use the 70's Chrysler external regulator, at least early PT's are same:


I'd guess someone full-fielded alternator to get it to work, and that subsequently caused PCM to fail, doesn't make much sense but this is the best I can do.

I would suggest finding someone will to work out wiring, then bite the bullet with Chrysler, doesn't sound like you're in a favorable position
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Old 28 Dec 2012, 09:59 pm
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Default Re: MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

WOW! It's so weird how a failed alternator can keep perpetually moving, but your clarification was so inciteful! Thank you! It's hard always being "that person" that has to probe and search and seem like a PitA to mechanics, but I feel much better, at east about surrendering this issue. At least my pcm is covered, and the rest will just have to get fixed without me feeling resentful someone is "getting me again!"... well for this to happen, someone did screw me, but oh well, it'll be the past, and the car will have warrantied service.

Im going to thoughtfully go over your information again and be better informed. Thanks so much for your time and awareness!
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Old 28 Dec 2012, 10:00 pm
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Default Re: MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

Also, they are "re-doing" the wiring as they have noticed cut wires that lead to "no where"
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Old 29 Dec 2012, 03:12 pm
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Default Re: MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

Bizarre-

Alternators do interchange (as mentioned) with other Chrysler models but the plug is diff on older cars; perhaps someone 'hacked' in an older alternator

It'd be very odd for someone to just change wires for no reason
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Old 20 Jun 2016, 03:27 pm
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Default Re: MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

I,m facing a similiar problem. I replaced alternator and battery.But it still wont charge the battery. So I ohms checked all wires from alternator to their destination all good still no charging. So where was your frankenstein wire. I will try that and see if I need an ECM(PCM). I know this cant help you but charging on these cars are a culprit i have seen all over the internet.
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Old 20 Jun 2016, 03:56 pm
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Default Re: MYSTERY! Wiring from Alternator to PCM makes the it run, WHY?... Help please

Because Trump
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sanatanadharma when you are no longer posting in stealth mode and make the availability for PMs then welcome , join and participate on this forum as a supporting member. Until then your responses in most threads will be temporarily removed.

Last edited by sanatanadharma; 09 Nov 2016 at 01:20 pm.
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