I have a trane a/c unit outside. I had switched the thermostat from cooling to heat. After awhile it started blowing out warm air. I just went to the unit and saw frost on the outside coils and the motor? What can I do to fix the problem so that we can have hot air blowing into the house?

I have a trane a/c unit outside. I had switched the thermostat from cooling to heat. After awhile it started blowing out warm air. I just went to the unit and saw frost on the outside coils and the motor? What can I do to fix the problem so that we can have hot air blowing into the house?
Sounds like you have a heat pump and it is working like it should.

Sounds like you have a heat pump and it is working like it should.
Yes I have a heat pump, but what should I do fix the problem. It's blowing out warm to cool air but it's not heating the house.

What is the temperature rise (supply air temp' minus the return air temp) and the outdoor temperature. Should be about 18 degree rise at 40-45 degree outdoor temp

The air coming out of the heater should be somewhere around 100 degrees to heat the house.

Have freon level checked. Compressor should not be frosting...

As Northern said, get a temperature reading at both a return and supply outlet and post it for him.