Posted: 7/16/2013 11:16:54 AM EDT
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I've exhausted just about everything including my search capability on this one - I figure someone here will have an answer or at least point me in the right direction though.
2001 Ford Ranger, 4.0 V6 - ~156k miles on it. About 10/12 I needed a new battery - swapped battery with no issues About three or four weeks ago I started getting intermittent battery light - it grew worse to the point where it it would come on and fan blower and lights would dim - then always on. I decided on swapping the alternator. Swapped the alternator for an Autozone rebuild about two weeks ago. Started the truck and no light - great. Went to drive to work that night and the light came on at the end of the block. Driving to my buddy's house last week the ABS light came on, then the airbag light - then lost tach - by the time I got to his house truck barely ran and had no electrical at all. We charged the battery off his truck and I was able to get home. Fiddled with it yesterday and got the idea that my battery was bad (had it out and on the charger but it wouldn't charge. Took it to autozone, tested ok but dead - they charged it, checked it and it came back bad. Swapped battery today for a new one - had them test the alternator at the same time and they said the alternator wasn't charging the battery at all - swapped the alternator in the parking lot for a new (not remanufactured) one Still not charging battery (light still on) New alternator, new battery - I'm going to rule out those being the issue. I checked the underhood fuses and haven't seen any that are blown. I'm starting to think it's my wiring (something I wasn't looking forward to checking out) Haynes manual says it could be a problem with "circuit A" which I assume is the A wire off the alternator but I have no idea where any of it goes from there. Ideas - trying to save the money of taking it to get worked on - have limited truck and electrical knowledge so barney style and pictures work best 
thanks guys I should add - NO starting issues (cranks right up no problem - as long as the battery has a charge) |
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The connection from the alternator to the battery should be fairly short and all accessible right under the hood. Check that path (circuit) and check the voltages (battery and alternator charging battery). I'd check all the connections, open them up, clean them and reseat them.
My guess from what you've said so far is a bad voltage regulator (too low) or bad diodes in the alternator (open circuit preventing charge). If you have no electrical knowledge, no tools and no repair manual, you should take it to someone for repair. P.S. - There are bad batteries, ones that go bad very quickly. |
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Quoted:
The connection from the alternator to the battery should be fairly short and all accessible right under the hood. Check that path (circuit) and check the voltages (battery and alternator charging battery). I'd check all the connections, open them up, clean them and reseat them. My guess from what you've said so far is a bad voltage regulator (too low) or bad diodes in the alternator (open circuit preventing charge). If you have no electrical knowledge, no tools and no repair manual, you should take it to someone for repair. P.S. - There are bad batteries, ones that go bad very quickly. I hear you there.... it's more "I hate tracing wires" than don't know electrical 
the regulator is part of the alternator so I'm on my third at this point - the terminal goes back into the engine (I think to the starter - I've been reluctant to pull the wiring diagrams, see above about tracing 13 year old wiring - I guess I'm going to have to do it. I'll trace that wire down and see about cleaning/resetting those connections though - can't hurt that's for sure. |
| Heavy cable off the alt may well go to the starter its a common + source for many manufacturers, remove and clean all terminals from alternator to battery and resecure tightly, also clean all major grounds. I don't have my Ranger or manuals anymore, but there's probably some fusible links coming off the + at the starter or battery feeding the cab and possibly some high draw underhood components, its not uncommon for them to fail when batteries and alternators do, may lead to charging problems, often lead to obnoxious things like batt lights etc, sometimes they do not burn in two but enough to allow some amperage, which doesn't cause all out failures which are easier to diagnose. Get to checking resistance and voltage drops with your multimeter. |
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the large black/orange wire and the yellow/white circuit A wire shows to go to the battery junction box and should go through some fusible links but they should have power to them at all times.
if the battery light is still on with engine running sounds like its probably a bad alternator most likely, or the light green/red wire circuit S coming from the indicator light is shorted to ground should have voltage at this wire with key on only. |
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Thanks for the info and ideas guys
I went out today with the wiring diagram and traced wires for a couple hours. All my grounds checked out good. Heavy cable off the alternator (black/orange) was good - continuity between the + battery cable and it. The white/black jumper was good and I know that the green/red one was good because the light on my dash comes on - that left yellow/white which goes to the power distro box. No continuity with it - pulled the wires apart and it was fine going into the top of the engine block. Found on the other side though it was completely corroded through. Pulled it apart (only hanging together by the insulation) and tested from there to the distro box - good (the fusable link was good then). Dug through the corrosion and tested back to the alternator plug and it was good. Quick trip to Autozone got me some 12ga wire, butt connectors and wire loom. Put together a jumper that passes the engine and it works just fine now. If you're having an electrical problem check your wires! |