alternator troubles??
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Mountain Pass
Joined: Feb 2002
Posts: 229
Likes: 0
From: Canada
alternator troubles??
(92 F250) Today my truck started acting up. When I start the engine my alternator belt squeals for a second or two then quiets. Voltmeter shows low, then after a few seconds swings up to where it normally runs (closer to the high end of the guage), as engine RPMs come up. After the engine is running for a few seconds and I'm driving, everything seems fine, until I shut it off and start it again. Is my alternator about to die, or is it just a regulator or something? Any help? Thanks in advance.
Postmaster
Joined: Mar 2001
Posts: 4,968
Likes: 3
From: So Cal
alternator troubles??
Could be a slipping belt. Check the belt for condition and or clean the belt and pulleys and adjust the tension(if there is an adjustment).
While the belt is off, turn the alternator by hand. It should turn smoothly and with light to moderate amount of resistance. New bearing may make the resistance modeerate. Older bearing will turn much easier. If you hear a grinding noise while turning, the bearings may be letting go.
I don't think a bad regulator would allow the voltage to vary the way I think you are saying.
What voltage are you seeing at startup and running and high idle?
I would expect to see about 12 volts right at the moment of starting and it should quickly climb to about 14 to maybe 17 volts just for a minute or two as the battery recovers it's charge which was depleted during cranking. Once things settle down you should see about 13 to 14 volts or so. When you turn the engine off you should see about 13 volts just from the battery. These figures are approximate so don't go wild if yours are somewhat different. You do not want to see less than say 12 volts or higher than 18 volts at any time longer than a few seconds.
Good Luck,
Jim Henderson
While the belt is off, turn the alternator by hand. It should turn smoothly and with light to moderate amount of resistance. New bearing may make the resistance modeerate. Older bearing will turn much easier. If you hear a grinding noise while turning, the bearings may be letting go.
I don't think a bad regulator would allow the voltage to vary the way I think you are saying.
What voltage are you seeing at startup and running and high idle?
I would expect to see about 12 volts right at the moment of starting and it should quickly climb to about 14 to maybe 17 volts just for a minute or two as the battery recovers it's charge which was depleted during cranking. Once things settle down you should see about 13 to 14 volts or so. When you turn the engine off you should see about 13 volts just from the battery. These figures are approximate so don't go wild if yours are somewhat different. You do not want to see less than say 12 volts or higher than 18 volts at any time longer than a few seconds.
Good Luck,
Jim Henderson
Junior User
Joined: Apr 2003
Posts: 91
Likes: 0
alternator troubles??
I had the same problem on my 1994 E150 with 5.0 just last week.
Check the belt tensioner. My snapped off. The bolt that holds them into the alternator/airpump frame can freeze up and then the tensioner can't function properly. Good luck.
Check the belt tensioner. My snapped off. The bolt that holds them into the alternator/airpump frame can freeze up and then the tensioner can't function properly. Good luck.
