1998 Ford F-150 Electrical Warning Light

GEORGE499

MEMBER
1998 FORD F-150
6 CYL
2WD
AUTOMATIC
145,000 MILES

I was travelling on the freeway at 70 mph and the battery warning light started to flicker. I dropped my speed down to 60 and the light went away. All appeared fine for the next 30 miles.

The next day, doing some in town driving (30 mph), the battery warning light was on constantly for 20 miles. On my return home, I noticed that to voltmeter dropped to just below half way (8 - 18.) And when I arrived home after 5 miles, the meter was reading 8 volts.

All electrical connections are clean and tight. The serp belt looks fine.

Could this be worn out brushes in the alternator or a faulty regulator?

I appreciate your help.

2 Replies

FLEXY5

MECHANIC
512 POSTS

It is most likely the alternator. You can pull it and have it tested. I would suggest testing the battery at the same time. The voltage regulator is integrated into the main computer, so it's not likely that is the problem, but we need to check the other two things first.

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Monday, February 11th, 2008 AT 10:51 PM

GEORGE499

MEMBER
2 POSTS

I pulled the alternator out and gave rotor a spin and it produced a raspy sound. I took it down to the local alternator / starter shop and had it bench tested. Sure enough it was pretty much spent.

Apparently the copper bushing where the brushes make contact is notorious for wearing out.

An hour and a half and $95 later I had the alternator rebuilt.

Problem solved. Thanks for the help!

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Sunday, February 17th, 2008 AT 8:44 PM