Hi I have a 1998 Explorer with the AWD and the 5.0 and the battery keeps going dead.It has a new battery and today It died on me again so I started checking the alternator out but I just want to confirm my suspicions before I drop 175 bucks.With the truck idling if I read the output on the alt to ground or battery neg I get 13 volts,turn on the headlights it drops to 12.6 volts some times it goes up to13.5 then back to 13.I got a jump and drove it home with no problems but 13 charging seems too low I assume the regulator is internal also? Anyhow thanks for any thoughts. Jason

 

I had a problem with my new battery going dead after sitting more than 3-4 days. My mechanic tested for a voltage draw and found the aftermarket alarm with a direct ground, I removed this alarm and reconnected the factory Ford alarm. No problems since. I watch him set up a volt meter to check for voltage drop but can't remember how he did it. Hopefully someone will chime in on the procedure. Good Luck.

Marty

 

Looks like it's not charging, should read around 14 volts at the battery with engine running.

I dont have wiring diagrams for a 98, but on a 97 the fuse to check is mini fuse 6 "generator/voltage regulator" It's under the hood in the power distribution box.

Probably the same on your 98, but check the fuse list in your owners manual.

 

Normally when running, you should get 14-15 volts. If you are sure you are using a good voltmeter and you don't have any fuse issues, then it sounds like you need an alternator. HOw many miles are on the truck?

 

Thanks for the replies I dont know what the heck is going on.I got it home and shut it off and it started right up.I checked it a while later and it was down to 9.5 volts and when I opened the tailgate for something all the locks started going crazy.I have it charging now and I guess once the battery is fully charged I will have to check for anything draining the battery and of course the alt. Thanks Jason

 

Don't forget to disconnect the hood light when checking for a drain.