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I'm working on a 2005 express van with a 4.8 and it came in with customer complaint that the car just died while he was driving and he suspects the alternator.
I jumped the car and brought it in. Battery failed a load test. Alternator was putting out 14.x volts and about 50 amps with some big loads on. I think it's a 100 amp alternator. I figured it was trying to charge but didn't have enough output.
I put on a remanned alternator and new battery and now the battery light is on. I didn't notice if it was before or not. Problem is that the ones we use from this rebuilder seem hit or miss.
There is a code p0622 generator field f control circuit malfunction showing up. With the car running and alt unplugged I get 10v on the brown pin. With it plugged in, and koeo I get .5v and plugged in koer I get 14.4v. The 3rd number, if I understand correctly should be changing from like 2-10v. The PCM should be cycling it on and off but it's a steady 14v.
The battery light goes on and off without any real consistency.
What should I test next and what should I have done before? I'm trying to get a better system for testing these types of complaints.
If the battery is goosed it may not be accepting charge so throwing any tests you do on the alternator off what is the battery rest, voltage idle speed voltage and loaded 2000rp voltages ? but it really sounds like an alternator internal issue.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Last edit: 7 years 3 months ago by Andy.MacFadyen.
I got it out this morning. The voltage on the L terminal was not right. I put the old one back in and the L terminal reading were good. I checked the F term and it had 130hz instead of 200hz. Not sure what to make of that but it wasn't the right spec.
We sent the alt back to the rebuilder, he gave us another and all was good.
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