I have a S70 T5 (130K miles) with an unusual problem. Just recently, the battery light comes on under full acceleration only. When accelerating slowly, it remains off. I just installed a NEW battery (old one was about 4 years anyway), and the problem remains. Could the alternator be "going bad"? Anyone heard of this type of problem? Thoughts? If I need to get a new alternator, any suggestions? PepBoys have an alternator for this car?

Thanks. Jim B.

That is about the exact opposite of what usually happens. Did you replace your battery because it died, or because of the light? When you did so, did the battery seem swollen? The reason I ask is this. At idle, the alternator is spinning at a slower rate than it is when you are zipping down the highway. This is why a LOW voltage happens at idle. So usually, the light comes on at low rpms. Yours is coming on at high rpms, indicating a normal charge when you are idling, and most likely an overcharge when you are accelerating. This will boil the battery. Generally, as in about 90% of the time, an overcharging problem can be corrected by replacing the voltage regulator in the alternator. However, in the undercharging arena, replacing the voltage regulator has always failed for me. So check your charging system and go from there.

I wouldn't buy an alternator from PepBoys. I'd stick with a Bosch alternator, or I'd have your current one rebuilt by a local auto electric facility that stands behind their work.

Chris

Probably not the alternator light. I bet it is the brake fluid
or coolant light. When they get a bit low, and you accelerate,
the dash light can trigger for a second. Well, it does if you
have a turbo model :)

Based on my experience, I'm placing my bet on slightly low coolant.

Good Call!!! You are corrrect. Mama "thought" it was the battery light. It was actually the low coolant light. Doh. We bought a battery that we probably didn't need. Oh well, the other battery was 4 years old anyway.

Just put in more coolant and water and the light went out. That's what I get for listning to mama without testing the car myself. Sigh...

Thanks all for the help!

Jim B.