electrical problem
#1
07-02-2003, 04:54 PM
Join Date: Jul 2003
Location: Durand, Michigan
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electrical problem
I have a 97 f-150 with a 5.4 liter that I have been having a problem with the charging system. I have replaced the original alternator with a NAPA 95 amp alternator (twice). I have taken it of and had it checked twice and both times it checks out to be putting out 14 amps. I have also put a full charge in the battery and had it tested which checked out fine. The problem I am having is when I start the truck the amp gage will read 13-14 amps, but after driving the vehicle for a short time it starts to fall off, down to 9-10. this is without running anything extra. If I turn on the blower and the lights it falls down to 9 right away. If I turn them off it will recover slightly, but eventually the fully charged battery is drained and I am sitting on the side of the road. My first guess was the alternator but the NAPA salesman doesn't think so. I have went thru and checked and cleaned every wire connection that has anything to do with the charging system. Does anyone have any Ideas? Thanks Bill
#2
07-02-2003, 06:24 PM
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Join Date: May 2002
Location: New Brunswick, Canada
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Well first of all to let you know the gauge on the dash is a volt meter not amps. If you are only getting 9 volts and the alternator is good then you must still have a bad connection somewhere. I'm guessing a bad ground. It sounds like the regulator in the alternator is going flaky. Unfortueatly it's one of those problems that will drag you in circles until you finally find it. Good luck.
#3
07-03-2003, 08:40 AM
I had the same problem with a 89 ford and all connections were good and the new alternator would charge as soon as I installed it then the second time I would start the truck it would quit charging. It turned out to be a loose connection in the dash wiring. There is a resistor across the alternator idiot light that is required to excite the field of the alternator and it wasnt making connection. There is a hole in the back of the Alternator that says "short here to test" When a wire is stuck in this hole and shorted to ground the alternator should start charging. If it charges when this connection is shorted then check all your wire connections as well as the dash connections . It took me a while to figure that one out.