Air conditioner issue

[Perd Hapley]

Early yesterday evening, we noticed that the temperature in the house had climbed to 80 degrees. The air conditioner just seems to have quit. I turned the thermostat to off, and turned the fan to on, but the fan doesn't even come on.

Possible causes? Please use small words; I don't speak HVAC.

I checked the fuse box (yes, our house has a fuse box, not a breaker panel), and none of them seem to have blown. My voltage detector chirping-beeper thing indicates that there is power coming in to the unit in the basement.

I also noticed that the condensation line was clogged, and some water had dripped down into the furnace. I cleared the line out. The line has clogged before, and we didn't have any issues.

We have the usual set-up; furnace in the basement, condenser outside.


That's about as far as I can go with my un-knowledge.

[Northwoods]

Don't know how diagnose those issues.  I just know we've a lot fixing our heat pump before finally replacing it.

[TommyGunn]

Maybe just needs a top-off of freon (or whatever PC chemical they're using as a coolant these days).

[Perd Hapley]

I had a guy check it out last year. He found it low on freon, and charged it. It could be low again, but I suspect there is a bigger problem.

[zahc]

If the unit is low on refridgerant, it won't come on. But the fan in the house should still come on. If nothing works, it makes me suspect either a fuse (but you checked that) or the thermostat circuit itself. Maybe nothing is telling it to turn on. Also, I have 2 big breakers on the furnace unit, in addition to the main breakers in the house service panel. Maybe check the unit itself for breakers.

[TommyGunn]

I had a guy check it out last year. He found it low on freon, and charged it. It could be low again, but I suspect there is a bigger problem.

Until I had a fix done my unit leaked refrigerant and had to be refilled almost yearly .... and the unit came on while low it just blew hot air.
Guess it thought it should have been a politician ........

[Jim147]

When you turn it to A/C what comes on? Inside fan? Outside fan? Nothing?

If nothing and you've checked power it might be a thermostat or low voltage wiring problem.

If just the outside fan comes on you may have a capacitor or motor problem with the inside unit.

jim

[zxcvbob]

If you have water dripping into the furnace, the evaporator may be frozen. (means low on coolant or the coils are dirty or the air filter is totally plugged up)

If the compressor is not coming on, check the disconnect box outside; it may have fuses.

It wouldn't hurt to clean the condenser coil fins.

[Perd Hapley]

When you turn it to A/C what comes on? Inside fan? Outside fan? Nothing?

Nothing. Thanks for the suggestions, folks.


And where is 280 when you need him?     

[never_retreat]

I know its 80 in the hose but does the unit produce heat it set in the heat mode?

Somewhere on the furnace there is a transformer that makes low voltage for the thermostat and is also used to trigger the relay on the outside condenser also. Hunt that down and see if it producing 24 volts I believe. You will need a actual meter for this not just a ticker.

Might be like this.



Another test you can do is open the cover up on the condenser and look for a big relay. They are usually fairly open style. Push down on the moving part with something non metallic (so you don't get zapped or short something) and see if the condenser comes to life.
If it works this means there is something wrong in the low voltage area. Ie transformer or t-stat.

Might look like this.



Is your t-stat manual or electronic? Is there a battery in the stat that could be dead?

Also depending on how old your unit is sometimes they have kill switches on the cover. Make sure you don't either a cover ajar or a bad one of these. You could bypass that if necessary.

[Jim147]

Do you have any info on the furnace you can give us? A model or a picture with the door off?

Good info from never_retreat so I'm going to repeat some of it.

If you have 120 Volts to the furnace, the problem should be low voltage. T-stat, t-stat wires, transformer pictured above or a board if it is a later model. The is also the door safety switch.

Don't forget to look for a light switch wired in beside the furnace. Maybe it got flipped off. It's there for service but never trust it to wired correctly without checking it first. 

Do you have a volt meter? If so we may be able to walk you through this without blowing up the house or killing yourself.

Maybe. 

jim

[Perd Hapley]

I haz multi-meter.

I have checked the "light switch," also.

I'll take pictures and check the transformer and relay tomorrow. Thanks much.

[280plus]

I went to a winery with the wife and in laws. So solly. Does the outside unit run and not the inside fan?

[Ron]

Will the thermostat make the furnace do anything at all? Will it turn on the fan? Will it turn on the heat?

[French G.]

The only time I played this game I had the same initial diagnosis, damn, house is hot. In my case I noticed I could trigger on both the AC compressor and the gas heat but nothing came out the hole in the floor leading to the easy diagnosis of a dead blower motor. One Grainger account that wasn't mine and a quick fix.

[MechAg94]

Mine wouldn't come on a year or two ago.  Ended up replacing the capacitor for the inside circulation fan.  I went through about 9 months of replacing capacitors on the outside fan, circ fan, and heater blower.  It is getting time to get a PM visit done.