I have a carrier weathermaker 8000. It is about 3 yrs old and yesterday I came home and the thermostat was completely off. I check to see if the breaker had been tripped. It had not. We tried a new thermostat and the ac still does't come on. What can I try next?

Thanks,
Cindy:)

Check your furnace,, breaker,and,fuse in furnace on the controle /circut board. The power to your tstat either comes from your furnace or a battery that has gone bad (inside the tstat)

Cindy,
Depending on your level of comfort with electricity, you may want some help with the procedure below. Refer to the attached drawing (which might not be exactly like yours).
The board is behind the blower cover.

1. Make sure the thermostat wires are all attached securely
   Secure - continue (you may have to open another metal cover, and now the danger level increases)
2. Is there 115 volts AC between L1 and L2?
   No - check power connections, since you said breaker wasn't tripped
   Yes - continue
3. Is there 24 volts AC between SEC-1 and SEC-2?
   No - the transformer could be bad (service call)
   Yes - continue
4. Check the 3 amp fuse
   Blown - replace with a 3 amp automotive-type fuse (take it with you)
   OK - continue
5. Is the (blower cover) door switch closed?
   No - close it
   Yes - How did you test the items above? :p

And before you do any of this, I would go the circuit breaker for the furnace and flip it off and back on, just to make sure it is reset. That might be all you need!

Best of luck, and be extremely careful.
WallyH