The car stalls when I turn on the heater

SHAKIMALENISE

MEMBER
2002 MAZDA TRIBUTE
0.6L
6 CYL
4WD
AUTOMATIC
100,000 MILES

Approximately 8 months ago I had the alternator replaced and purchased a used battery in great condition. Car runs great for about two days and then it just won’t start. I got a jump it started up fine and took it back to have the battery replaced. He checked to see if the alternator was charging the battery and it was until I turned the headlights on. He changed the battery again and said until I can get a new alternator don’t run anything else on the battery. As soon as I turn the heater on the car stalls and as quickly as it tries to stall it will rev back up when I turn the heater off. Going back I had the alternator replaced about a year before and completely forgot. What is going on?

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,716 POSTS

Hi,

You know, it does sound like a weak alternator. I need you to do a simple check. Follow this link for checking an alternator. I want you to have a helper in the vehicle while checking to see what the voltage at the battery does when you turn the heater on.

One other thought. On vehicles, if you have the defroster on, the AC compressor will turn on to help dehumidify the air entering the vehicle. It's even possible the compressor is locking up and stalling the engine. That is only a theory at this point. But to be honest, the heater in and of itself, does nothing other than the blower motor drawing power. That's why I'm thinking it is a weak connection at some point. Does the blower actually turn on?

https://www.2carpros.com/articles/how-to-check-a-car-alternator

https://www.2carpros.com/articles/how-to-use-a-voltmeter

One more thought. If you have a weak connection at the battery or the main ground, that too can cause an issue, so check those things as well.

Let me know what you find or if you have other questions.

Joe