My AC is not working. I tried switching the breaker and tried replacing the fuses on the outside box. The key to all of this is that the thermostat refuses to even turn on. It is digital, not batter powered, and it does not have a read out. Does this mean a simple power problem somewhere along the way?
Is there an inside unit and an outside unit? There usually is a separate plug in for systems where the inside unit is. This would power the thermostat.
May want to check that the inside unit is plugged in and that the outlet is working. Plug a lamp into the outlet to test.
Other than that, call for service...
I tried fooling with the outside unit some more. The helpful guys down at Ace hardware suggested I reset the compressor and see if that helps. I am having trouble finding the compressor reset button from the view I have now, but I am taking a break for a bit (I live in AZ and it's crazy hot outside, espescially right in the sun) and will remove another panel of the unit so I can see what's going on.
My next thought is to go buy a ladder and go into the attic and check the power. But I don't know what would make it stop working suddenly if it is merely a power problem. I'm betting on the compressor, but don't know why the thermostat would not have power, then.
If this reset doesn't work, I'm going to see if I can replace the thermostat for cheap. Good luck, right?
The thermostat runs off the 24vac transformer, usually in or near the air handler.
Could it be a bad breaker then? I tried replacing the fuses, which did not work. I checked the old fuses at ACE when i returned the new ones and they said they are working fine. The only easy-to-fix thing I can imagine is the breaker. But when the AC first shut down, we checked the breaker and the AC breaker was not tripped. We reset it anyway, and that did nothing. So we did all these things. I'm out of ideas, but hate to have to wait two or three days so an AC guy out here can charge me a couple of hundred - the peak season rate, of course - to fix what seems to be a simple problem.
It does indicate a power problem but it could be any one of several things. even a bad Tstat.
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If the the thermostat was working, and now it does not have a display, that seems to indicate that the thermostat is not getting power.
As others have indicated, the thermostat usually runs off of
24 volts AC, which usually comes from a line voltage-to-24v transformer in the air conditioning unit.If the thermostat has power coming in, but doesn't light up, I would suspect the thermostat. If there is no power to the thermostat, the problem is further upstream.
Could be a broken or bad connection from the transformer to the thermostat, or a transformer failure.
If you're not comfortable reading schematics, using a volt- meter, and poking around electricity, it's time to call in a professional.
Jerry
Only do what is outlined below, if you are certain you can work around
240- volts safely! If not find someone that has a lot of experience working o electrical circuits! Buy a multitester, "Set it at 250-volts AC" and check for 220 to 240-Volts on the control contactor in the condenser.If there is 220 to 240-volts AC there, leave the tester set at 250-volts until you know you are on low voltage then set it to a lower AC voltage. Then check for 24-volt there and at the furnace. If there is NO
24-volts there, it could be a manual reset cutout open in the 24-volt circuit open. Turn the beaker off and on, on the condensing unit too. Some units have two Transformers, and there and one at the furnace.Do NOT take any chances, 115-volt circuits can kill you deader than a hammer! - Darrell
Are you _sure_ it's not battery powered? If so, then it's almost certainly powered by a 24V transformer somewhere. Find that transformer and confirm _it_ is getting power, and that it is outputting 24V to the low voltage circuitry. It is probably on a different circuit from the AC compressor itself, so will be associated with a different breaker.
Assuming you have the manual for the thermostat, you might be able to figure out which wires control the AC and see whether the AC starts if you short them together. That would clearly point to the thermostat as the culprit. But don't proceed unless you're sure you've got the right wires. :-)
Go buy a volt meter. Open the air handler and see if there is 120 volts coming into the transformer, if there is then check other side of transformer for 24 volts, if no voltage (24m) then replace transformer, if you get 24 volts then look for a 3 to 5 amp automobile type fuse in the circuit board, if it is blown then replace it. If it blows again then there is a short somewhere in the 24 volt circuit, most likely in the transformer or the two wires that come off of the circuit board and go to the contactor on the outside unit.
It never has a read out? Or it usually has one and doesn't have one now?
If the latter, maybe. Nothing from ##### down is relevant unles the problem is the latter.
Do you have a furnace too, in the same unit? Try turning your furnace on.
As to the AC, try changing the temp that the AC is set for. First down, then up, then down again. (I would suggest different things if you seemed to be used to using a meter, etc.)
If you have the manual for the AC or the thermostat, or you search the archives of this group, it will say what the colors of the wires to the thermostat are. Out of several, you connect two, and the AC should go on.
####### If the AC thermostat depends on power from the AC, I had that 2 months after I moved in. No AC, no 24 volts. The 24 volt transformer was built into the end of the controller box (the unit is now 27 years old. It was 4 years old then.) and they wanted iirc more than 200 dollars for the controller box. At the AC supply store, I asked if they had just the transformer, and he didn't have one as small as mine, but he did have one that was bigger. Maybe 20 dollars. But I don't know if your controller is made like mine, and if it is, you have to be able to find the transformer, find the output places on the circuit board, use a meter to verify that the 24 volts isn't there (while the AC is on, but not a risk if you don't cut into the 110volt wire that is on the other side of the transformer ),
Stop here. You have to verify that their is 110 to the input of the transformer and no voltage out. If both of those aren't true, it's probably not the transformer. I only have one house, and in my limited experience, that's the only part that you can replace that might be the problem. But if it's not the problem, replacing it is a waste of time and money. Get a digital volt-ohmmeter (multimeter) maybe at Radio Shack. Don't get the once that are especially small. Get the one that costs between 15 and 20 dollars iirc.
.... then buy a 110volt to 24 volt transformer of sufficent size, turn off the power, mark all the wires by color and location, remove the control unit, remove the old transformer, mount the new transformer somewhere in the AC box, and run two pairs of wires from the new transfromer to the places where the old transformer was connected. 2 wires with 110 volts and 2 wires that get connected to the circuit board where the old transformer had its output wires connected. make sure you don't connect the transformer backwards, that you have the
110 volt side connected to 110 volts.I used the last one's advice and it totally worked. Replaced the transformer and it's back on! Thank god, it was getting hot in Tucson this week. No idea why it did that or what happened, but this house is something like ten years old and the outside unit was replaced last summer, but the transformer was our old one, so it's probably something to do with that.
Thanks everyone -- awesome group!
First, you should post this on alt.hvac, the guys on that group can give you what you need.
Second, replace the thermostat sounds like exactly the right thing to do. Be sure to ask for help on color codes for the wiring.
From your several posts, you don't have the skills to troubleshoot and diagnose. An AC guy may be your only answr. Or go to Walmart and buy a couple window units.
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Strange electrical system with BOTH fuses and breakers!!!!
Contactor in compressor could be bad. In mine, the original installer had left a pair of of pliers inside the contactor compartment. 10 years later, something bumped the cabinet and the pliers fell onto the contacts.
Lots of reasons why no cold air. If fan doesn't start and compressor doesn't start, its 24vac for thermostat and contactor coil, or a bad thermostat.
If compressor runs and fan doesn't, then bad thermostat. If fan runs but compressor doesn't, less clear whether that is thermostat or something outside in the compressor case.
Nope, not so strange. In my experience, there is usually a manual disconnect near the AC unit with cartridge fuses inside.
Jerry
Here we have manual disconnect only, no fuses
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