2003 Ford F-150 Alternator overcharging

ALECS

MEMBER
2003 FORD F-150

Electrical problem
2003 Ford F150 6 cyl Two Wheel Drive Automatic

My mother drives a 2003 Ford F-150. Lately it has been having trouble starting. I used a volt meter on the battery while the truck was running and saw that it was 18 volts. It is 15 volts when the truck is off. So I checked the alternator and it was putting out 18 volts. The first thing that came to my mind was the voltage regulator, I am pretty sure it is in the alternator on this vehicle. So, I replaced the alternator and the batter just for good measure, but it is still running at 18 volts. Any ideas?

2 Replies

MHPAUTOS

MECHANIC
31,938 POSTS

Hi there i found this test, try it and see what you come up with.

Mark (mhpautos)

Was this

answer

helpful?

Yes

No

Friday, October 10th, 2008 AT 5:45 AM

ALECS

MEMBER
2 POSTS

I completed the fiirst test and my results were.4 volts. The alternator is grounded on the engine itself and the regulator is integrated in the alternator. I believe on this model the regulator ground is controlled by the ECM/PCM. I am not sure on this. I am pushing toward a ECM/PCM replacement, but that can be very expensive. Do you have the specs for what the ground levels should be at on the regulator harness? OR actually the ground testing procedures for testing the regulator?