[mrsA]

My thermostat was reading low battery this am. New batteries were placed and now the air conditioner does not go on. My husband went and bought a new thermostat and it still does not go on as well as the heat does not work either. The fan from the furnace will not kick on. What could be the problem?

[stanfortyman]

Bad control transformer?

[mrsA]

What is a control transformer?

[stanfortyman]

The HVAC tech that you call can tell you.

[westnlas]

Check the circuit breaker to the HVAC. The transformer may be bad. It is the component that reduces the voltage to dc that goes to the thermostat. Usually located in the attic. Perhaps, since your husband was able to install the new t-stat, he could check the voltage at the wires going into it ? No voltage with the breaker on would point to a broken wire or bad transformer.

Calling a service tech is expensive and may not solve the problem. Techs do not benefit when things work, only if they break. I had to get 2 different companies to fix my AC this year because the first guy was an idiot, and I was afraid of damaging the compressor motor.

[stanfortyman]

Usually located in the attic.

Not at all. It is usually located IN or on the unit.

Perhaps, since your husband was able to install the new t-stat, he could check the voltage at the wires going into it ?

Since a t-stat is simply a switch, WHERE is he going to check for voltage? You do not have both sides of the transformer secondary at the t-stat. He would need to check for voltage AT the control transformer.

Calling a service tech is expensive and may not solve the problem. Techs do not benefit when things work, only if they break.

Are you serious?? This is simply your opinion from your own one bad experience.
OBVIOUSLY something IS broken, or they would not be posting this problem here.



The thermostat has been replaced. Still no worky. It's time to call in a pro.
If you're afraid of getting screwed then call some friends and relatives and get some recommendations.