Volkswagen Repair: 1984 Rabbit battery not charging, pepsi coke, v belts

Question
1984 Rabbit.

Two problems which I think might be related. For the last couple weeks it has been making a screeching sound like a belt is slipping, but only when it is in gear and it stops after I put the clutch in. I can rev the engine in neutral and it doesn't screech.

In the last week, the battery has not been charging. There isn't enough juice to turn the starter. Last night, I jump started it, then drove for 10 minutes, and parked it for a couple hours. After that, it started, I drove it for a half hour, parked, and tried to start it immediately, and it wouldn't start. While I was driving, the radio was intermittently going out.

So my theory is that the v-belt is slipping, and not turning the alternator, which is causing the screeching and the dead battery. Does this make sense? Is there a good way to test this out? The v-belt doesn't seem too worn--it still has good "teeth", but it may be somewhat loose. There is around 3/4" of play.

Thanks a lot.

Answer
Jonathan, thank you for your question.  By what you are describing, it does sound like the belt is loose.  The typical play in a v-belt is usually about 1/8” – 3/16” of an inch.  At the same time, check the connections on the battery for any corrosion.  You can clean the corrosion with baking soda (Arm and Hammer type) or with a Coke or Pepsi (coke for some reason is better to remove crystallized battery acid.)  After cleaning off the acid then clean off the terminals (both the post and the terminal).   If you have a side post battery you will still need to verify that there is no corrosion.   There is a possibility that the alternator is beginning to fail.  The only way to test this is to take the alternator off and take it to an auto parts store that has an alternator tester. Usually v-belts are good for 18 to 24 months, so if your belt falls within this timeframe, you may want to replace it before it breaks on a deserted highway. Damaged v-belts are very hard to tell if they are good or bad. Many years ago (over 25 years ago) one could just check for cracks but that is no longer a good indicator.
Hope that helps