2002 - Intermittent Battery Light - Alternator and Battery New | Ford Thunderbird club group 1955-2005 T-Bird models

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2002 - Intermittent Battery Light - Alternator and Battery New

R

Racer27

Bronze Member
Reaction score
7
Thunderbird Year
2002
Shop replaced the Alternator as it tested as defective (Red Battery Light). After a couple days the Red light came back, so I tested the battery and it was marginal (65%). Since it was 3-4 years old replaced it with a new Motorcraft 750 Group 66 vented battery. 1st drive this morning, Red light came on again, only to off after a 1/2 mile. Car only has 13,000 Miles, don't see any signs of corrosion. I have an appointment to bring car into shop that installed the alternator. Any suggestions as to possible cases/fixes?

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You would need to put a voltmeter on the battery with the engine running to see what the alternator is putting out. It should be at least 13.5 volts. The alternator circuit is pretty simple. If it's not a wiring issue then it's possible the replacement alternator is faulty. Did the original alternator really test bad or did they just go by the dash light. The alternator should be tested off the car to make sure it's defective. Many shops are just parts changers because it's faster. Alternators don't usually go bad with that little miles.
 
Totally agree with most shops being parts changers. They said they tested it, on the car, and said output was low. When I tested the old battery before replacing it yesterday, it was marginal, the one test if failed outright with a voltage of 11.9, was engine off after lights were on for 2 minutes. Battery was at end of life anyway, so no issue with its replacement. Shop said belts were fine, no slippage, and have to assume everything was reconnected/installed properly.
 
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