can an alternator be checked while in car
If the weather is cold or your battery is old, your battery could be the issue and your alternator might be just fine. That's why you need to check the battery before checking the alternator. Here's how to do it: Turn off the car. You'll want to make sure your engine is off before attaching the voltmeter.
Check the alternator amperage Disconnect the voltmeter and connect an amperage meter (if you aren't using a multi-meter) to your battery the same way as you connected the voltmeter. Turn on all the electrical equipment in the car: lights, stereo, wipers and everything else you can. Let the engine idle at around 1200 rpm. Check your car's manual or parts manual to see what your alternator's maximum amperage should be. The amp reading on your meter should be near the maximum output.