01 Explorer Sport Trac Overcharging

[Kevin1968]

My Explorer is driving me crazy. My alternator went out on me. I replaced it and the battery. Now its charging at 18 volts. I took the alternator off and had it tested. Its in specs and charging perfect. I re installed it back on the truck and it is now charging at 18.9 volts. Both the alternator and battery are new and I have had the alternator checked twice ( after I removed it ). Off the truck it is working properly, on the truck it is overcharging. I had the battery tested and its ok . Im lost as why its overcharging. HELP!!

 

[koda2000]

If it's really overcharging the only thing it can be is the voltage regulator on the back of the alternator (or maybe your wiring, but IDK how). Are you confident your voltage tester is accurate? is the gauge on your dash also pegged?

At 18.5v your battery should be getting hot and will eventually start smelling like rotten eggs.

 

[Kevin1968]

It is definitely overcharging. 2 different testers and dashboard light confirms it. The wiring cant only be installed 1 way. I just cant figure why its charging fine on the counter at autozone, And overcharging installed on the vehicle.

 

[koda2000]

It is definitely overcharging. 2 different testers and dashboard light confirms it. The wiring cant only be installed 1 way. I just cant figure why its charging fine on the counter at autozone, And overcharging installed on the vehicle.

Have you tried examining and wiggling the various plugs on the alternator? Maybe you have a bad connection somewhere and the voltage regulator isn't seeing the state of charge of the battery. In addition there are fusible links (several IIRC) that may be burnt out. Was there any drama experienced that preceded this situation that you haven't mentioned?

If it were me I think I'd try a different alternator, regardless of what the Autozone's machine is saying. Almost 19V is awfully high no matter what.

 

[hondaslave1342]

Interesting..keep us posted

 

[boominXplorer]

Exchange it or return it and go to napa. I've had problems with every chain store alt and starter brand new but auto zone and advance take the lead in brand new pos' out the box.

Forgot to add the voltage regulator is in the alt and the pcm monitors it but won't ask it to charge at 18v.

 

[Sport100]

Check the ground circuit in the Alternator & Battery wiring harness.

 

[delexploder]

Did you check the pully diameter?

 

[koda2000]

Did you check the pully diameter?

I don't believe that an over-sized or under-sized alt pulley would cause overcharging. The charging rate is up to the voltage regulator. Anyway this thread is 4 months old now, so I guess the OP figured something out.

 

[delexploder]

I've seen them over charge when ran constantly over driven like it kills the regulator but it also just points to low quality store brand junk