AC malfunction

[pcgondreau]

I have a Rheem central air conditionor in the model series AKA (full model# is RAKA-042JAZ). I operate it by turning the thermostat up when I want it off, and down and when I want it on. Lately, there has been a delay of up to several hours or even a few days between turning the thermostat down and the unit turning on. There other day, for instance, I heard it kick in and turn on at midnight after I had turned the thermostat down two days before. Last night I turned the thermostat down so the unit would run over night, but it's yet to kick in.

Any ideas?

Thanks in advance for any possible help you might provide me with.

[JWWebster]

new thermostat needed is my first thought.

[pcgondreau]

New thermostat for inside the house, or new thermostat on the air conditioner somewhere? If for the house, any ideas how I'd go about doing that?

Thanks.

[Repair-man]

The wall thermostat pretty much determines when the unit comes on. Replacement thermostats are at any Home Depot, Lowes or better supply houses, and they all have instructions in the package.

[JWWebster]

There is nothing but your wall thermostat controling that big old monster ac you have. It is done by low voltage such as a doorbell would run on. The delicate controls that determine the temperature are never subjected to the rough and ready power that drives that puppy. Change your thermostat.

[RegUS_PatOff]

or you could do a voltage check to see if your thermostat is closing the circuit, or you could just try shorting the correct wires together to test if the unit turns on.

[JWWebster]

Touch wires together: ruin heat anticipater...not good.

[pcgondreau]

I would I do the voltage check?

[Repair-man]

Let's go back to your original complaint, the unit not coming on. When you say unit, does this also include the inside blower that is supposed to come on along with the condenser outside?

If both the blower and the condenser do not respond, you have low-voltage issues involving the thermostat circuit. The thermostat voltage is supplied at the furnace by means of a transformer. Generally there is a small fuse on the newer systems which protect the circuit from overload, so look inside your air handler for this and examine the low-voltage connections at the furnace.

You can test the thermostat voltage at the furnace where it all connects together. The red wire from the transformer is your 24 volt source to the wall thermostat. This must be measured against the common terminal on the transformer to properly ascertain the voltage. At the wall thermostat, you can also check for 24 volts between R and G, for instance. This will use the common side of the fan relay as "ground" for the test. Do you have a fancy digital programmable wall thermostat, or is it the plain no-frills design?

[pcgondreau]

The inside blower works without any issues. Does that change what you say about the voltage?

I have the older no-frills thermostat, but I got a new digital one as per J.W.'s recommendation. I have yet to change it, though.

[Repair-man]

Every detail you provide not only speeds things up for you but at the same time keeps this forum topic from becoming a bit chatty and drawn out  .


The problem will be somewhere outside, most likely. The LV wires to the condenser are often cut by trimmers, chewed by dogs and rodents, etc. Go out there and carefully examine the wires to the unit (LV) all the way into the control panel to the contactor. A single loose connection under a wire nut somewhere can ruin your day. Check the contactor for signs of fire ant infestation and/or burned contacts while you're at it.

You can also attach your voltmeter leads across the 2 LV wires out there and go inside to set the thermostat to "cool". The reading should be 24 0r 25 volts to the wires at the unit. If voltage is present, replace the contactor. If no voltage is there, the thermostat may be at fault. Pay attention to the new thermostat wiring instructions when you get ready to replace it. Sometimes they need a jumper here or there, and they are all different in setup.

[RegUS_PatOff]

just for clarification, that's 24v or 25v AC

[pcgondreau]

I forgot to update you on my situation. I changed the thermostat as J.W. suggested, and that solved the trick. J.W., you the man! You helped me fix my washing machine in the winter. I can't begin to estimate the oodles of $ you saved my from dishing out to repairmen for both jobs! Thanks a million!