nanjemoycat

This week-end I had to turn on the AC. It ran fine but would not cut off once the set temp was reached, I had to turn off the breaker once it got cold and turn on when needed. This morning I woke up in a oven, AC running but blowing hot air. Turned off the unit and let it sit a couple hours and turned it back on. It blew cold air for 30 minutes and then cooled off to the point of blowing hot air again. I went out and bought then installed a new thermostat. No change in operation, 30 minutes of cold air than hot. It's an outside unit AC/propane heat all in one about 17 yrs. old. Any ideas?

tbouknight

sounds to e like the condenser fan aybe overheating after run time.. very commom problem .

baypro21

Have you gone outside to look at the unit once it starts to blow hot air? Is the condenser fan motor still running? Is the furnace firing generating your heat? Your original problem was the a/c would not cut off and the house got too cold til turned off at the breaker? But now it puts off heat after 30 minutes? The way you are decribing it, it sounds like 2 differant problems. Time to call a pro.

Justaguy2025

Check to see if the coils on the air handler are dirty. That is the inside unit either in the attic or closet. I bet they are freezing up. Either they are dirty or you may be low on gas.

HardLivin

Had the same problem last Saturday. The air handler (inside unit) was freezing up. I discovered this on Sunday morning. I let the unit completely thaw out. About 2:00 PM we hooked up the tank of R22, turned my unit on and set the temp around 60. The unit took a big drink of R22 and now I have cold air again. I've got a leak we haven't found yet, I bet you do to.

nanjemoycat

Problem solved. I ran the unit again to see if the condenser was freezing up. When I went outside to look, I noticed a thermostat wire that ran from the heat unit to the A/C unit on the exterior had been mangled, stripped and mashed together. Best guess a weedeater from Sundays grass cutting. Thanks for the suggestions all.

s_ebels

Could be low on refrigerant........... restricted air flow will also cause the symptom you are describing. Both will cause the evaporator coil in the furnace or air handler to ice over.If the refrigerant flow metering device is a thermostatic expansion valve rather than a fixed orifice that could be sticking. If you have a heat pump instead of straight A/C only you may also have a problem with the reversing valve.