Why won't the main fan motor shut off or change speed?

Has the breaker been replaced? Is the breaker the correct amp rating?

Check the emergency shut off that is outside the house next to the condensing unit.

You are tripping that outlet's breaker. Either too much is on that breaker and circuit or that circuit is not big enough, enough current to power that unit.

Replace the capacitor inside the control panel on the outside unit. The top of the capacitor may be puffed up.
The fan motor may also be going bad. Change the capacitor first. It will have to be changed anyway if the motor is bad.

The indoor fan or the outdoor fan? If it is the indoor fan the thermostat may be wired incorrectly or shorted. If the red wire and green wire in your thermostat maintain contact, the indoor fan will run all the time.

You have a direct short in the A/C unit probably at the compressor or your condenser fan motor. You can disconnect one component at a time to identify where it is shorting. turn power off unwire condenser fan motor secure wires so they dont touch anything plug unit in if it still pops breaker your compressor is probably bad.

Hello, usually this happens when the pressure switch remains open, this could be due to a blocked flue pipe, water inside the tube between inducer motor and pressure switch, or the switch itself is going bad. Condensation can form and leak back to the pressure switch through the tubing and causing an intermittent problem with the inducer motor running continuously

Hi, here is the theory on the reset button on Air Conditioners. They reset via the breaker panel box in your house. Check that first before anything else. However if your unit is popping breakers, it is because the rating for the breaker is incorrect, or there is something that needs servicing usually in the outside unit called the condenser. That piece contains the compressor. A faulty compressor and pop the breaker. Or If the condenser fan that blows over the coils of the outside unit stops (common failure) The compressor will overheat and shut down. That may not trip the breaker but the house will get hot anyway. Usual action for this is to replace the condenser fan motor and starting capacitor. Make sure the speed rating and directional rotation for the replacement motor is the same as the motor removed.
There are other reasons why the system won't come one fully. If the wall thermostat is digital and does nothing. including turning on the fan. There will be a small fuse located on the circuit board of the air handler (part of Air Conditioner mounted inside the house. It houses the circulation fan). That fuse could be blown. That one shuts down just about everything.
On air handlers mounted up into the attic crawl space there is an overflow pan. This pan is mounted directly below the air handler. This pan can fill with water when the drain pain contained inside the air handler starts to overflow because the drain system to that is clogged.
There is a "float switch" mounted in the overflow pan wired to the system in such as way as to shut down the entire AC system if that pan fills.
The handling is to clear the obstruction in the Drip Pan inside the air handler. Then remove enough water from the overflow pan and the AC will run as though nothing has happened.
If you have more questions, write to me on this site.
One thing more. The capacitor alone in the Outside condenser unit can fail and that will stop the condenser completely if it is of a "split" design and used for both the compressor and fan. When replacing this unit alone, ALWAYS find the same specification part.
I hope this helps,
Have a Happy New Year,
Mark

Does the fan turn freely? Some oil might help but it sounds like you need a new fan motor.

hello elanalex,
When your heater shuts off it trips your main breaker and that is usually associated with the interupt capacity of the breaker ( which means that while your heater is drawing current, if the thermostat says stop.. you are interupting that current demand abruptly and your getting a surge back to your breaker, You may be able to add a surge arrestor to that power feed to suppress that problem. You may also be able to repsecify your main breaker with one that has a higher interupt capacity.. Check with a local electrical supply house..explain the problem and they should be able to provide a hardware solution. Make sure you provide details on your circuit breaker brand so they can provide the proper solution.. GoodLuck
Regards,
Rick