A weak car battery can cause your auto air conditioner to function poorly or not at all. Car batteries need to have enough voltage to trigger the AC compressor, and while it may be strong enough to run the rest of your car, it may still be too weak to run your car’s air conditioning. Bacteria Build-up.Click to see full answer. In respect to this, can your AC drain your car battery?The simple answer is that if your engine is running, and your cars electrical system is functioning properly, then “no,” air conditioning does put an additional load on your battery. Your battery will drain, as the alternator isn’t spinning (producing electricity), and therefore the regulator has nothing to manage.Additionally, how long can a car battery run an air conditioner? This means that a car battery can run an air conditioner (assuming an inverter is used), but it would like only run less than 10 minutes. Additionally, why is my car AC so weak? Very often a low air flow and weak a/c ac is caused by old cabin filter that does not allow enough air to go through it and that way the a/c will feel weak. Most of the cars have cabin air filter so always check that first if you have weak a/c, it takes a few minutes only.Can the alternator affect the AC?If your alternator is failing, this can cause many electronics in your vehicle to quit working. This includes the engine, the air conditioning, the radio, the windows, etc. Once the alternator has been replaced, the air conditioning is likely to work again.