Battery light

mercury
sable

#1

2000 Mercury Sable wagon, 3.1 DOHC engine with 140,000 miles. Battery light came on, mechanic said that it was the alternator. Replaced the alternator, and now the battery light comes on intermittently, especially when loading the engine (going up a hill). Mechanic checked the output of the alternator and said that it was putting out correct voltage. What could be causing the intermittent battery light?


#2

The serpentine belt could be slipping. Belt dressing could be used to test for this.

The battery cables could be loose or corroded.


#3

Thank you… I had the mechanic clean and tighten the cables. Waiting to see if the light comes back on.


#4

The battery light did not come on for two days. Yesterday it came on three times in 5 minutes. This time in normal driving conditions, not loading the engine as in going up a hill. No noise from the belt slipping. Any other ideas???


#5

Your replacement alternator could be bad.
It could be the wiring to the alternator.
It could be the ground strap to the engine.
It could be the PCM (probably not, but possible).
It could be wiring under the dash.
It could be an issue with the instrument cluster.
It could be the battery internally shorting (unlikely).
(This assumes that the battery cables are okay and the belt and tensioner are okay.)