5.0L (1979-1995) MustangTechnical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.
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Started, drove down the streat to a gas station to grab a coke on my way out to have an estimate done on getting a new paint job on it, and it is DEAD. Jumped it, drove it out to have this guy give me the estimate, had to jump it again, drove to auto parts store, they said bat was fine and alternator was screwed. Was charging 52 amps instead of 75. I know little about alternators. Does that sound right? The idiot guage showed it was charging normal, but if I shut the car off and then tried to restart it, it was hyst dead. IMMEDIATLY was dead......
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take a dvom to the batt. with the car running you sould see 14.xxx volts.. if not the alt is probibly bad as for amps it depends how they tested it and what was on in the car during the test (lights radio heat wipers) keep in mind the auto parts store testers can be misleading especially if you get the FNG who almost always gets sent out for batt. tests
1992gt 5 speed stock bottom end with an E303 cam, aluminum gt40x heads, tubular intake, plenum spacer,19# injectors, 70mm bbk throttle body, bbk CAI, bbk 76mm maf , shorty headers, flowmasters, accel coil, and 4.10 gears
A 75 amp alt doesn't charge 75 all the time. That is the peak charge. Check connections. At the batt, the starter, the solenoid, everywhere. Corrosion can easily build up between the clamps and posts. Gauges can be misleading so do as ben said and check voltage while running.
Sometimes when a battery goes bad it happens suddenly with no warning. I just had one replaced in my moms Lincoln for her under warranty because it just suddenly stopped taking a charge. generally I wouldn't expect the altenator to be putting out no more than 20 or 30 amps with only the car idleing and the radio on if the battery is charged. Probly up to about 40 or 50 amps if the battery is dead and its working hard to keep it charged. I would have the battery tested with a load meter to see what it pulls down to. I bet that battery under load drops to 0 volts in less than a second.
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