I have two a/s units and one wont come on. I turn the thermostat controller on and it clicks like it should as if the a/s is starting up.Nothing happens. I have checked the fuses and also checked if it froze over. But neither are an issue and Im in Houston so its not frozen. I dont know what else to check.

 

Does the blower work if you set the switch to run instead of auto?

 

I tried just the fan and still nothing

 

check the switch on the side of the furnace and check the breaker

 

does the condensor and fan turn on outside. If your any good with a voltmeter you can check to see if the condensor is getting power. There should be a panel were the main power line goes into it. It should connect to a box at the top( can think of its name) check to see if its getting power to the top and also the the bottom of that box.
But also can you provide more detail about what is working or not working with the unit.

 

Check the voltage on the outside unit to see if it is getting juice.

You could take a VOM, and check the 24 volt relay system at the condenser coil also. Just to see if the thermostat is sending the signal.

Here, we sometimes get fire ants in the relay contacts, believe it or not. It's kind a common problem.

 

If the fan isn't running the outside unit will not start, there's a safety interlock involved.

The thermostat should click, the fan should start, then within 15 seconds the compressor should start. If your fan isn't starting, I'd look at that part of the system first.

 

Yes, the fan is started by relays.

 

This is crazy. I didnt mess with it today. I went upstairs and turned the thermostat back on and it started right up.

Thanks for all the info. Ill keep an eye on it for now.

 

you might check the wires on the furnace/air handler where the thermostat wires hook up. usually this is small gauge bell wire that cracks from vibration where the insulation was stripped and the wire gets knicked. ive found this on friends furnaces. last summer my ac would not come on. got the meter out and started checking for power. turns out the emergency switch on the side of the furnace, that is never used, must have gotten butchered up on install. the plastic was cracked because the ears on the switch were bent back. this had been like that for 10 years. repalced the switch and it was good.