If you have arrived here, the breaker to your air handler is tripping. There are a couple different things that can cause this. To troubleshoot, you can try to reset the breaker; if the breaker immediately trips you should not reset it again. 

Here are some common problems associated with tripping breakers:

- You could have a burnt wire or burnt component somewhere in your air handler that is touching the cabinent of the unit, causing it to trip.

 - If your air handler has a heat strip, it could be shorted or grounded.

 - Sometimes wires in the service disconnect or the whip going to the air handler short, causing the breaker to trip.

 - There could be a component in your air handler pulling high amp draws over a period of time, causing the breaker to trip.

 - The breaker itself could be going bad if it trips after running for a period of time. This is less likely to be the problem in a situation where your breaker is immediately tripping after being reset.

In all cases, a service tech should be called to diagnose what is causing the breaker to trip.

The below image is an example of a Square D breaker that has started to go bad.