Charging system woes

[stamp11127]

With the engine running, measure the voltage at the alternator output stud and the alternator case. If you have 13.5 - 14.5vdc that alternator is fine. The problem is then in the harness from the stud to the battery. If not then time to check the two wires as stated in an earlier reply above.

Also check this thread, reply 16, for a solution:

http://www.expeditionforum.com/thre...4l-check-charging-system-message.33535/page-2

 

[Red88LX]

Ok. I guess no one has any ideas? So, I will ask another question. I read something on another thread that speaks of a sense wire. "The pcm may not be getting the correct voltage on the sense wire it uses to determine if the alternator is charging.
Check for voltage on pin 3, brown wire of the connector on the alternator. You should have battery voltage with the engine off."
Do I perform this test with the KOEO or with the key off? Any help is greatly appreciated. I am currently thinking of swapping the alternator again. I also see where several other people have had to swap more than once or twice with the rebuilt units.

 

[Red88LX]

Sorry stamp. I refreshed the page but for some reason it did not show your response until after I posted again.
The reading at the posts is 11.86v. Even with the battery charger on and running with no accessories on. Still 11.86. I will check out the link you sent and check back.

 

[Red88LX]

Is the C192 the same as the #3 pin (brown wire) on the alternator?

 

[Red88LX]

I put a quick charge on the battery. 12.05 between the battery posts with the engine running and the exact same between the stud of the alt and the casing. The brown/pink wire has no voltage. KOEO. But, the harness is new and I had the same problem with the old harness. I mean I had the same no charge problem. Do I need to pull the plug on the alternator and check the alternator pin itself? Or does this mean that there is a problem between the harness and the PCM? Thanks again.

 

[06 Eddie]

I've read in other forums and threads and I've mentioned this myself I think but to share again there have been many reports of auto stores alternators simply not performing and everyone including myself who switched to a Motorcraft have had their issue cured. I've read about 2 or 3 replacement alternators that don't work or work briefly and again instant cure w the MC. Didn't seem likely to me as my voltage tested acceptable but a little weak and I figured a new alt would be a new alt but like many other people I'm now solid. Of course I paid for it ($350 compared to autozone $200).

 

[stamp11127]

Most people & shops don't have a stand alone oscilloscope to test the signals on the two circuits (1930 & 1931) to determine if the pcm is receiving and sending the signals needed to operate the alternator. They usually will throw an alternator at it and say your old one was bad but you have more problems that they can't find if it doesn't work.

A multimeter doesn't respond fast enough to the various signals so it is useless at this point unless it can show duty cycle.

Your call on tossing a new alternator at it. If you do I would go with a known brand - ac Delco or Motorcraft.

 

[Red88LX]

I won't bore you with the details of what else I tested. But it came down to the 3 wire plug at the alternator. When I push down on it I noticed it immediately responded on the MM. It dropped again after I let off. I ended up using a ziptie to apply pressure until I come up with a better fix. It was really just by luck that I noticed it.

Thank you for all of your help. It was very aggravating but at least it is fixed. I also learned a few things about testing that I had never had to do before. Just reading through the other threads on this helped a lot. Most of the answers were by Stamp11127. Thank you for any help you offered to me and the others along the way and thank you for your patience.

Now while I was under the engine checking the positive wire on the starter I noticed anti-freeze on the back of the A/C compressor and on the wire loom going to the starter. So, I may be on here again soon if I can't track it down myself.

 

[stamp11127]

Thanks for the update.

If the latch on the plug isn't secure enough I've put a very slight twist on each of the male connector pins that it plugs into. The idea is to have a redneck interference fit.

 

[LsxBigDeddy]

Had this same problem and it was one of the fuse links in the harness. I just jumped the constant 12v from the alternator plug to the battery lug on the alternator and my light went out and system began charging around 13.7v