My thermostat keep shutting off altogether. No reading or anything. After a day of so, it will click back on by itself. Usually when I've had the controls in the off position rather than cool or heat. Once it comes back to life I can turn the ac on but it normally goes out again within a few minutes. The ac is working fine when the thermostat does.

Any suggestions?

If it has batteries, try replacing them. If it has a B or C terminal, make sure it is properly connected to the B or C terminal at the furnace. Also make sure the red wire is supplying 24 volts to the R or RC and RH terminals.

If you have good batteries and good connections, the thermostat may be bad.

Okay, I used my tester and it doesn't appear I'm getting 24 volts to the thermostat from the red wire.

The red and blue wires should connect to a transformer in the furnace. Usually they connect to R and B or C terminals at the furnace. Sometimes the transformer is protected by a fuse in line or on the circuit board. If it has power to the AC feed from the house, and isn't giving the 24 volts, replace it. Should have no trouble finding one, hardwares, home centers, or even Radio shack has them. Just get as high or higher rating, amps, watts, or VA.

Thanks, I appreciate all your input. I'll check the unit connections. I live in Florida and have a Trane ac.

I am having the same problem. We had power outage which blew the fuse in the furnace. Replaced the fuse and the thermostat turns on, but every time I switch it to Heat or Cool it cuts off. It will run when I switch it to Emergency Heat.

I'm thinking it's the T-stat because of the power outage. I was wondering what BMartin had to do to fix his problem/

Thanks.

If you have a furnace, you can do a quick check by connecting the red and white wires. The furnace should immediately start its heat cycle and run until you disconnect them. If it does, the problem is with the thermostat. With a heat pump, it would be more complicated. See the sticky at https://www.askmehelpdesk.com/heatin...ons-58313.html

Thanks for having the confidence to send me an email, but Ttop and Acetc can give better answers than I can. I cut back when Northern Heat joined a year ago, but haven't seem much of him lately. At least we still have the great sticky he put together.

Labman thanks for responding.

Friday night I went under the house to look at the wiring and see if I could figure it out. Well everything looked good, so while under the house I flipped on the disconnect and waited to see if the heat pump would start back up. I sat there for a second waiting then BAM!! A big white light jumped after me. Needless to say it scared the sh*t out of me and I nearly knocked the house off it foundation trying to flip off the disconnect again. Well after I regained my composure, I noticed the flash and bam came from the heat pump's transformer. Knowing that I was now in over my head I called a HVAC pro the next day.

He looked at it, replaced the blown transformer but couldn't find out why it blew. When he first tested the wires the Green on was showing a short in the wire. He cut off the end, reskined and wrapped and the short seemed to go away.

Right now everything is running fine. It just makes me nervous that he couldn't tell me what cause it.

My robert shaw thermostat is stuck on emergency heat and I can't get the a/c to come on. It just stays in emergency heat.