1985 Chevy Caprice Station Wagon - alternator, battery, and starter all tested. Battery was so low it was replaced for a brand new one. starter showed fine. alternator tested on machine and said "good". BUT on the car, alternator shows as low voltage - Brand new alternator on car showed as low voltage. Anyone have any ideas what it could be and how to fix it - please and thank you
I'm not the best at electrical stuff but check grounds, check grounds, check grounds. Running you should have a battery voltage measured at the posts of about 14-14.5. Off you should have 12.5 - 13 or so. If the alternator checked good at the store and in the car isn't keeping the battery up and assuming the voltage regulator is good then it could be a bad positive cable on the battery or a bad ground on the alternator. I'm also assuming that the voltage regulator is separate from the alternator. The alternator should be providing 17-18 volts to the voltage regulator. If it's internal the alternator output should be right around 14 volts. Just thinking.
I had the exact same problem with my '84 Delta 88 with the 307 V8. Maybe they're the same engine. Changed the alternator and battery and still low battery and I was getting stranded all over the place. It turned out to be a bad belt off the main crank pulley. It was slipping. There are two belts and you have to remove the alternator belt to change the main crank belt. I also think it was a worn pulley on the crank. The belt also squealed when it went bad when you rev the engine. I had to change the belt every few months because there was no tension adjustment. I think that belt drove the water pump and power steering. Then the alternator was driven from the water pump. Check it out, its a cheap fix if you can do it yourself.
I have been told the belts and the tension on them are all good. I'm gonna look into the regulator and the ground wiring. Thanks.
The local parts store is NOT the place to get anything checked out. Look in your yellow pages for Automobile Electrical and find a place that fixes things as a professional specialty, rather than one that sells parts. They can go in and wiggle the wires and diagnose the problem properly. We can only shout ideas and opinions, but if you don't have the any experience there can be a steep learning curve when it comes to automotive electronics. StorminNorman and I took his alternator to a parts store to be tested and it failed. Then took it to a real shop, and it passed fine, was not the problem, $175 saved.
