Hi Guys,

I had the A/C unit running fine today... then all of a sudden my thermostat went blank... It was raining on and off today here in Plano, Texas...

It is a Carrier A/C furnace unit, controlled by a Honeywell Thermostat... This thermostat gets its power from the unit itself... In the past, last year when I had similar problem, it was the auto-shut off the switch I had up in the attic, near the unit. I also had to replace the fuse on the board in the unit last year...

FYI... I had to replace the overheating Fan Motor and Capacitor on the condensing unit 10 days ago... But it was running fine all last week with the new fan motor and capacitor... so that may not be the issue...

Now, how do I know what the issue is? It is not the circuit breaker and it is not the switch upstairs either... I checked the fuse in the board, it looks good on surface... I don't know how I can check it out... How do I check if I need to replace the fuse? What else do I need to check? ANy help will be greatly appreciated... Thanks,

Arvi.

I'd start by checking low voltage wires inside the furnace, Start with "R" and "Common", Something may have been bumped or pulled loose since you just replaced the motor.

I just replaced the fuse on the board on the furnace/ac unit... it didn't help...

Also, when they replaced the motor, tech worked just on the outside condensing unit... He didn't even go/look at the unit on the attic... Could there still be an issue with the wires? I checked the wires I can look at on the board... didn't see anything there... What else can I Check? Please let me know... Thanks.

Did the tech. remove the cover from the thermostat? Check there for any loose connections. What type of fuse is on the control board?

Do you own a voltage meter?

No I don't have a voltage meter... Also, tech didn't remove the cover of the thermostat... I just now did open the termostat, (after it went blank) and cleaned and put it back as it was... I didn't see any loose connections there... ANything else I can check?

Open the cover back up on the thermostat, disconnect the red and green wires, twist them together, Did the blower come on?