battery light & 3500 rpm
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Junior Member
Joined: May 2003
Posts: 6
Likes: 0
battery light & 3500 rpm
I have a 2000 F150 XLT 4x4.
When I am driving and push the engine to about 3500rpm the battery light comes on.
Can anyone give me ideas on why this is happening.
Thanks
Betaman
When I am driving and push the engine to about 3500rpm the battery light comes on.
Can anyone give me ideas on why this is happening.
Thanks
Betaman
Technical Article Contributor
Joined: Apr 2003
Posts: 345
Likes: 2
From: Central NJ
sounds like a voltage regulator problem. They are on the alternator and can be replaced but the alternator needs to be removed first
hook a voltmeter to the battery, it should read somewhere around 13.5 volts at normal idle. rev the engine and if the voltage increases to OVER 15 volts, the regulator is bad.
also if this is the problem, have the battery checked out as you may have "cooked" it
good luck
hook a voltmeter to the battery, it should read somewhere around 13.5 volts at normal idle. rev the engine and if the voltage increases to OVER 15 volts, the regulator is bad.
also if this is the problem, have the battery checked out as you may have "cooked" it
good luck
Senior Member
Joined: Feb 2001
Posts: 496
Likes: 0
From: Chicago Burbs
I had a similar thing happen with a 1976 E350 with 460 and 90A alt. Every time I got the highway with the 4.10 gear and no OD it would stop charging. When I slowed down to 30 mph or so it start charging again. Near the end I had to tap the alternator with a hammer to bring it back to life.
I finally had to replace the alternator and had no further problems for the life of the truck.
I finally had to replace the alternator and had no further problems for the life of the truck.
Senior Member
Joined: May 2001
Posts: 219
Likes: 0
From: Richarson, TX
I had a car that would only charge properly at low engine speeds. The symptoms sounded like those that ChiDiver just described. Very tough to locate because the voltages indicated that the charging system was working fine but the battery would slowly loose its charge when driving. It finaly turned out to be a loose v-belt and a worn alternator pulley! It's not as likely to happen with todays serpentine (sp?) belts. Now I always check to see that the belt tension is tight enough that I can not turn the alternator pulley by hand with the belt installed.
Senior Member
Joined: Jan 2003
Posts: 357
Likes: 0
From: Festus, Missouri
i had that prob on my 00
had an 00 xlt w/ 4.6 and the bat light started coming on at high rpms, then got to where it was coming on around 2,000 rpm. they told me i had a bad altenator. if you still have some warranty, i would take it in asap, it only gets worse. looking at my reciept, it cost a total of 264.83 installed. good luck.
