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91 explorer sport 400,000 kms 4.0L new alternator 4 months ago charged perfectly til now. it just totally quit charging this morning, it used to do this randomly for several years then we put the new alternator on and thought we had it beat. is there any place where the power source for the field has issues or any other ideas why this beast keeps on having this reocurring problem. all the battery cables are clean and tight as well as the 3 connections on the alt itself
Before you condemn the alternator, use a VOM and check for relevant readings at the 4 wire connector (known to crack and deteriorate) and at all the main wires connectd at the battery (known to corrode inside the insulation)
well when we pulled the old alternator the brushes and comm rings were pretty total fubar, so we figured that was the issue.it ran perfectly since replacement up til now
Does your replacement alternator have a good warranty? If it does you should be able to get it replaced for free if it's faulty. I had one go bad only a couple of days after I put it on, but it was exchanged for another one and no trouble for more than two years now. Some times it's just the way they are. And that's why they have a warranty. Do the other checks like has been suggested to make sure other parts are ok though. Let us know how it goes.
12.6 with battery freshly charged, obviously the connection to battery is good but the alt is not putting out.is the new alt no good or there something screwy with the wiring
There is a hole in the back of the case, when you insert a nail/small screwdriver it shorts out the regulator, should give full output 15/18vdc. if it does the regulator is dead, if not the brushes/stator/exciter circuit is faulty.
you should see 14.2(+-) with a good battery/alternator.
yeah i found the spot on the back of the reg. after i took the alt off. we tried the alt off his f150 it works perfectly so i guess it was the alt after all. thanks guys