flashing battery light

well, today i went to pass a car, and when the rpm's went higher, the battery light started to flash, and the headlights started dimming.. i cannot even begin to imagine what is wrong with the truck.. i took it to advance, and they tested the battery and said it was fine, and the alternator also was fine.. have any clues of what it could be?

Can you duplicate the symptoms by just reving up the engine while statonary?

Mark

i dont believe i can, it only seems to happen when im driving the vehicle

Check all the wiring, check for a short or open. Check to see if any of the harnesses are rusted out, and check if the pins in the harnesses connect properly and stay that way. Is there a check engine light?

As you put more load on the engine, it will tend to twist more on the engine mounts. This will pull wires and may casue a chaffed wire to short or a poor connection to become open circuit.


Mark

no check engine light..

Get a wiring diagram. Check power to and from the alternator and battery.

the guy from both advance and auto zone, said that it seems llike my alternator is starting to go bad, could this be something too.?

Yes that is a possiblity. But id still check all the wiring just to make sure. You can never be too sure and go without testing something. Because what happens if you buy a new alternator, and it wasnt that, but a simple peice of wiring.

96 so is the belt slipping at high rpm - stretched or the tensioner worn out? Just a thought due to the rpm cause.

I thought that but if he can't simulate the effect by reving the engine when stationary I started to think of other reasons. I have the seen the engine torque effect on chaffed wiring before. I had a Vauxhall Viva HC in the UK. A wiring harness passed under and was clipped to the oil pan (yes a great idea). Eventually this harenss would chaffe through. There were two wires in this bundle. The oil pressure light and the points to coil connection. Driving home one night my oil light started to glow. I could make the light glow brigher by accelerating as the engine twisted on tne engine mounts and as I lifted my foot off the gas the light dimmed and went out. My girlfriend had the same trouble but this time it was the points wire shorting, so as she accelerated the engine would cut out. Easy when you knew where to look but those cars were so much simpler and easier to work on. Of course they needed constant attention to keep them running efficiently.


Mark - the old timer

i revved the engine while stationary, and the light did come on.. it didnt flash like before, it just came on until the engine calmed down..

Did you measure the voltage on the battery? I have seen a faulty alternator be OK at low revs but bring on the battery light at higher revs. I would still look for a wiring problem as suggested amd also slipping belt. Is it better or worse with the lights on.

Do some more checking. Hate to waste money on an alternator and find that you still have the problem.

Mark

I would bet money on the alternator brushes. They can be inspected.