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Ok. This is a somewhat strange problem but I will try to include all the details. The battery light on my 1991 Saab CD turbo (automatic) is coming on very easily. It comes on during acceleration, stops around 45 mph when it shifts into 3rd gear, but always comes back on around 55-65 mph. When I accelerate very lightly it still comes on, and of coarse comes on when
. When accelerating moderately the light only comes on briefly right before gear shifts. I don't belive it is a fault in the battery light itself because when it's on, the headlights dim, and the console dims. I've noticed recently that there is a squeaking noise that comes from the engine compartment as the car is being started and as it idles. When it hits about 55 mph and the battery light comes on, it's only fixed by releasing the pedal and letting it coast back down to 45, where the light goes right back off. Also the problem in general seems to occur less when the engine is cold, and the battery was tested and works fine.
Any suggestions are appreciated. Thanks in advance.
 

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Do you have a battery meter in the saab computer? Does it show what the battery is running at whilst driving the car? Should be 13volts or more to charge a 12v battery.
It does sound like you may have an alternator problem- squeaking could be the belt if too tight or too loose etc

hth
 

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Or if the belt is OK, try checking the state of the alternator brushes.

On a 12 year old car, they could be worn enough to be losing contact occasionally which would cause the battery warning light to flash.

Or the alternator or battery could be dying.
 

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Sounds like the belt is loose and it is slipping. If you can get your hand in there, try turning the alternator pulley with the engine off. If you can turn it, the belt is too loose and is slipping in the pulley groove. Should be able to adjust the alternator bracket to tighten
 

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I would have thought a tensioner pulley.

Correct, automatic tensioner fitted on that model. Looks like you have a dodgy alternator. Get a multi meter and connect across the battery with the engine off, you should get about 12v, start engine, you should get about 14.4 volt approx, rev engine slowly thru the rev range and monitor the voltage reading, if it keeps dropping back then increasing as you increase the revs there is a connection problem or intermittent fault on the alternator regulator. Check all connections for corrosion first.
 
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