'99 Explorer Charging System Problem

[Aupl8ed]

replaced alternator (salvage yard), replaced Battery. For three weeks the truck started fine..but as time went by you could tell it was getting weaker. You can watch the volt meter in the dash and see that it's charging sometimes and sometimes it isnt. I put a brand new volt meter to everything and I cannot find in reduction in voltage anywhere and I tested everything from a common ground. I guess my next step will be to replace the belt. Perhaps the fact that it's charging at time and not others is becuase the belt is slipping, though it seems plenty tight and there is NO noise comming from it no matter the RPM's. If you 'goose' it a bit from a dead stop, the volt meter in the dash will move up as though its charging, but as soon as you hit the next gear and the RPM's drop, the needle will drop significantly...nearly all the way down. However, even at 'dead' (no clicking, no attempt to turn over...nothing) windows and cd player, locks etc...still work and the very second I put cables on it to jump it..it will start...there is no 'charging time'..it starts immediately and will run for as long as you like. Turn it off and it may start again...it may not. There IS NO METHOD TO THE MADNESS! It's driving me nuts. Does ANYONE have a clue where to look next?

 

[aldive]

Have you measured the voltage ( with a VOM ) at the B+ terminal on the alternator and at the battery?

If so what was the voltage reading?

 

[Papa]

Your dash-mounted voltmeter should NOT be jumping all over the place. The DC output voltage should be roughly 13.5 to 14.7 volts. A lot of places will check/test your battery and alternator for free maybe even the place you bought the used alternator from. You may also have to look for a fusible link in the positive wire coming off the alternator.

 

[Aupl8ed]

Have you measured the voltage ( with a VOM ) at the B+ terminal on the alternator and at the battery?

If so what was the voltage reading?

I did test with a brand new VOM however I cannot recall then what the reading was. I can tell you as I mentioned in the post that I did not find a loss of voltage anywhere (ex. 12.4 at the battery, 12.4 at the wires, 12.4 all the way to the starter) 14 plus coming back off of the alternator.

 

[Aupl8ed]

Your dash-mounted voltmeter should NOT be jumping all over the place. The DC output voltage should be roughly 13.5 to 14.7 volts. A lot of places will check/test your battery and alternator for free maybe even the place you bought the used alternator from. You may also have to look for a fusible link in the positive wire coming off the alternator.

I had both the battery AND alternator tested at Autozone..they both tested good. I finally concluded that perhaps my battery was sulfated and swaped it out for a new one. Truck started like a champ for a couple of weeks, then nothing. I have checked all of the obvious things like lights being left on overnight etc....When I originally tested all three components, I pulled the starter out, pulled the positive cable all the way out, reconnected everything and tesed...I did not see any fuseable link in the positiven wire. Unless you are talking about the giant fust that the cable splits off and runs to from the battery post...I tested the voltage there as well and there was no reduction in voltage.

 

[410Fortune]

You are missing one component of your charging system, the wiring.

I suspect you need to replace the battery cables, both the + feeds to the starter solenoid (where they meet up with the alternator + charging wires) and the ground wire to the frame and engine.

At least do a thurough checking of the wiring and terminals.
You can completely remove the alternator harness from the truck and check it out, then remove the battery and start working backwards from there on the battery cables....

Check all attaching points for the ground leads, the cables can corrode from the inside out.

 

[CDW6212R]

You have checked just about everything. FYI, the voltage while running should be way over 13.0 volts, no matter what is operating. If you don't have that much, go straight to the alternator. My 91 Explorer with a stock 2000 alternator runs over 14 volts, under absolutely all conditions. The later alternators are much better than the old ones.

I agree that you should look hard at all of the cable connections, especially the battery terminals. BTW, tell us that you do not have any bolt on replacement battery terminals. Those are absolute garbage, they have caused far more trouble than any other part in the charging system. If anyone has them or considers them, don't. Only use one piece battery cables. Get them from Ford, or have them custom made. Good luck,

 

[Papa]

The 14 + off the back of the alternator should be the same on top of the battery not 12.4 VDC indicating you have a bad or broken electrical connection/wire in the negative or positive wiring. Example if you take a DCV reading from the alternator B+ and put your other lead on the battery + the DCV reading should be 0 VDC you are going to get a reading of about 2 to 2.5 VDC. Do not forget to check you negative connections where they bolt to the block. At least you know your alternator is working.