Carrier thermostat went blank, not working. No battery to replace. Checked fuse in air handler and it is OK. What could be the problem?

Carrier thermostat went blank, is not working. No batteries to change. Checked fuse in the air handler and it is OK. What could be the problem?

Check to be sure 24 volts is available at the thermostat.

Not sure how to do that.

Not sure how to do that.

I hate to say this but if you do not know how to test electrical circuits you might be better off contacting a local professional to look into your problem unit with a visit to your home. I am afraid if I tried to explain to you how to use an electric meter to do the testing here I could not be complete enough to prevent you from damaging the meter or yourself during the test procedure.

How did you test the fuse? OR did you just look at it?

Thank you... I am trying to get pro out here. Been all weekend with no air. Thank you again

I have a carrier non programmable thermostat. Do you know what other therm might be a compatible replacement?

I have my carrier thermostat set at 79 for cooling. A couple of days ago the thermostat showed it was 83 in house and AC kept running and temp stayed at 83 even though it is set to 79. Now it won't go below 81 and never shuts off unless I set temp to 82. Any help would be appreciated.