AC broke... any ideas what to check?

[hairy_apple]

Figures... it starts hitting 90 and the AC fails me. It first did something weird a couple weeks ago, turned on the AC and nothing happened. The thermostat clicked but the AC never started blowing. After an hour or so it did however and worked normally after that.

Then fast forward to this week... it's just stopped working all together. Both the heater and the AC the thermostat clicks, but doesn't actually come on. So we replaced the thermostat yesterday... and it is still doing the same thing.

Now, sometimes it does come on (after being switched on hours before) and when it does, it works fine... until it cycles back off and then it never starts up again. Last night at 2am it came on and was blowing cold and the compressor sounded and seemed normal.

I'm am new to this home ownership thing, never worked on HVAC and know almost nothing about it... any idea what might be wrong with it. I really don't want to call someone if can avoid it, I'm pretty poor right now but also not too excited about going through summer without it either.

 

[LAMBCRUSHER]

okay, sounds like a possible pressure issue...which means call a good AC guy. if there is not enough or too much refrigerant pressure, the condenser/fan won't come on. it *could be a phooey contactor coil or even loose wire...shut off breaker and disconnect and open terminal box and give it a good once over...ohm across the coil of the contactor...it should have some resistance and be a fairly stable value. of course, check for loose wire terminals...if any wires are connected with wire nuts, might crack em open to make sure the conductors are making good contact and that the nuts are on good.....look for an extra box on or near the AC unit or disconnect....in calistanifornia, the utilities have a special time/usage box that serves as a disconnect for the AC. people signed up to get a better KWH rate to have these types of headaches installed on their cooling gear....they open the control circuit based upon time of day/ rate of usage of the surrounding grid...


NOW, if you check out the terminal box, and it all looks good, and there is no "extra" boxes attached, you should have an AC guy out to check your pressures and the rest of the circuit. if you're not comfy with things like ohm meters and contactor coils, you should have an AC guy out to start there...if you have an extra control box, call your utility company...

in addition...there should be some sort of transformer to take line voltage down to 24VAC to take to your Tstat...that transformer could be going south or have a bad connection...to rule that out, you'd set your t stat to on, and read voltages at the AC to make certain it is indeed getting triggered to do anything. this is deadly dangerous as the circuit will have to be on to verify this as well as the termination box open, and your fingers in it...best to cal an AC guy.

short of a bad board/ compressor motor, a good guy should have it figured out and fixed fairly quickly.