Alternator swap issue - need an electrical guru

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davy crockett

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I thought I lucked out, my factory alternator was on the way out and I got my hands on a 200 amp alternator out of a 2010 Crown Vic Police Interceptor. Everything looked like a match except for the charge terminal and regulator plug locations being swapped.

I installed the new alternator but I got a check charging system error right away and the battery light was on. I scanned the truck and got a code of P0620. The alternator is charging but only at around 13 - 13.5 volts.

I tried a second known good cop car alternator and it does the same thing so the alternator isn't the issue. I know these trucks use the PCM to control the alternator operation and the code indicates a interaction fault between the PCM and the alternator so I'm suspecting for whatever reason the PCM doesn't like some feedback it is getting from the alternator. I have updated the PCM to the latest calibration as per Ford's TSB # 04-14-9 but no luck.

I like the factory 200 amp alternators because they are a solid piece and so many of the aftermarket ones are junk. With some of the upgrades I have planned for the truck (dual batteries, inverter, winch, audio system, lighting, etc) the extra capacity would be nice to have.

I'm hoping someone might have a more in depth knowledge of how the system works and if there is a way to make this swap work properly.
 

stamp11127

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A quick look at the diagrams shows the pcm is different between the years. I'll look at it in more detail tonight and let you know.

You may nave to use an external regulator.
 
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davy crockett

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Thanks for checking into this stamp.

What I don't get is what causes the fault if the alternator is outputting voltage within what the PCM considers an acceptable range? That link indicates only abnormal voltage should set the code.

If the PCM wants to see a higher output does it command it from the alternator? I guess I don't understand fundamentally how the PCM/alternator relationship works.

Right now the alternator charges but not over 14 volts and I'm not sure why. The TSB also refers to putting some di-electric grease on certain connectors, which I'll try as well.
 

stamp11127

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One easy way out of this may be to see if a 200 amp alt was offered on the Police CV's in 2004. If so we can check the diagrams to see if they are compatible.
It looks like you have a mismatch in the electronics between the two years.

Yep, Rock Auto shows one for the 2004:

MOTORCRAFT Part # GLV8647RM

On a side note:
I'm not saying that this is your problem but I was looking into a used BMW X5 a while back. Came across a thread that the user stated that you need to update the electronics with battery info when you change one out or it doesn't start. Don't know if it is true but WTF is that crap??? The manufacturers are getting a little carried away with this electronic stuff if he is correct.
 
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DrMaestro

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I just put in a 350 amp alternator from a 99 super duty. (Still aftermarket?) Anyways, im having the same issue. Same codes and "check charging system" message. Will not charge more than 14 volts. Im doing the big 3\4 here this week, maybe that will do the trick? Looking forward to figuring this one out.
 

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