voltage drop


Old 03-21-03, 03:51 PM
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voltage drop

This one will be fish in a barrel for you guys...
On my '84 Cutlass, 307, auto: things run fine until I turn on the defroster, then the juice just drains out, and stalls the car.
The problem is there when I use the radio; as well. It just doesn't drain the battery as fast. (minutes, as opposed to seconds, with the defroster)
I got it started back up, and revved it up awhile to get the volts back up, but by then a storm was coming through and I had to quit.
I haven't tried the AC yet, so I don't know if that's a factor.
Belts are fine, I don't think the battery is 'enough' for the car, though. (small-I don't see any cranking amp or anything written)
Also, The wipers don't work. I haven't checked the fuses, yet.
Do I need an alternator; battery; both? Can I do the "pull the pos. battery terminal" test, without doing any damage?
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Old 03-21-03, 09:22 PM
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Sounds like it could be the alternator not charging your battery sufficiently...so I'd check the alternator. You can simply go to any autoparts "chain" like schucks/kragen/checkers, autozone, napa, etc and ask them to test it (you have to take it out of the car first!).

You can also check the voltage across the alternator when the car is running. It should be at 14V...anything less *could* be the voltage regulator.

Now several concessions here: Is your engine bay dirty? sufficient oils/fluids/etc could be affecting your alternator. What about the wiring? Are all the ground wires good? Are the connectors for the ground wires good? Any rusty connectors for ground wires should be replaced.

BTW- If it is a bad alternator and your battery has been undercharged for a significant length of time your battery might be ready for replacement soon as well. You don't have a severe lack of power do you (on the engine)?
Old 03-22-03, 01:43 AM
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I agree and, WELCOME patryuji!!!!!!!!
Old 03-22-03, 06:21 AM
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The alternator is likely wasted, replace it with a good AC Delco rebuilt, or have someone competent completely rebuild your original.

If the battery is more than four years old, it's likely wasted too. Replace it with a Delco as well.

You can do an alternator output test as noted in my "The Basics" below.

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