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Need help diagnosing volvo

I have a 93 volvo 240. It runs fine around town, but when i run the headlights and/or accessories, lights start to dim and abs, srs, and a light i have no idea what it is comes on, then i lose power. same thing happens when i drive on freeway, even with no accessories on, until i lose power and have to pull over and let charge. do i need to replace alternator? any help is greatly appreciated.

Lose power as in the motor can’t keep the car going? Or lose power as in no electrical power? The alternator is what charges the battery. When charging issues occur the alternator can be the problem, but there are diodes in the alternator that can go bad, and a voltage regulator (sometimes the regulator is a separate unit, and other times it is integrated into the alternator), sometimes it is a loose drive belt, sometimes a battery going bad will not hold a charge and pulls a lot of current from the alternator.

Your problems could simply be a loose drive belt, so start with checking that. Then get the battery load tested. Finally check the alternator. Some auto parts stores will do the checks for free.