My friend has a 01 Mazda B-2500 that when he's siting in traffic or idle the battery voltage drops like it wants to die but when he starts moving again it goes back up. He took it to the dealer ship and they tested his alternator and they said it was good his battery is new and we can't figure out what is causing this to happen. Do ya'll have any ideas? Any information would be helpful thanks.

 

Has anything been changed on the belt pulleys. If he has changed any of the sizes it might slow the alternator down to were it does not charge at idle.

 

i don't think they have been changed but I'll ask him and get back to you.

 

I would take off the alt and take it into autozone, have them test it for free. Don't trust dealerships.

I think the alternator/voltage regulator is in the process of failing.
It can test good one minute and be bad the next.

side note. My buddys f150 has a charging problem its because the bus bars in engines electrical distribution box wont make contact unless you have it tweaked just right. it either ate up three alts. or we got extremely unlucky and received 3 faulty alts.

 

i told hi to tack it to auto zone last night but don't know if he did it or not.