I have a '91 Integra LS hatchback with 157k miles. The battery light has been on for a few days. The battery is only 6 months old. I’ve only driven her around the corner to the store a few times. I’ve been measuring the battery voltage with a digital multimeter. It started out around 12.25V and is now down to 12.05V. I checked both the battery and alternator fuses and they are ok. I think the problem is either the alternator, the alternator belt, or the battery. What can I do to isolate the alternator and tell if it is the problem (vs the battery or belt)? Also, what is the minimum battery voltage required to be able to start the car?
take voltage reading with the car off the start it and check it again. With the engine off you should read around 12.1-12.5v. With the engine running it should be around 13.8-14.4v. If you are getting the same readings with the car on that means your alternator is toast. Check your belt slack by grabbing the belt and tug on it a little to see the deflection. You should have about 1/2in deflection if i remember rite. Im almost certain that you alternator is gone. Most 90-91 integra’s with around 120-150k miles are when the alternator decides its done for.
i once paid $150 just for labor to have it replace at the shop. after it was done i started experiencing dimming of my lights when i went past 4k rpm but never went back to complain cause it was done out of town. the darn alternator lasted only about 3 yrs and went out. so i got it replacement free of charge and this time i opted to put it in myself. taking it out took me a good 1-2 hrs but putting it back in only took about 30mins. i did everything from the inside of the hood so i didnt have to jack the car up or take off any wheels/axles. you will have to loosen your brake master cylinder and a few brake lines. if decide to do it yourself and want more details on taking that sucker out and putting it back in, let me know.