I came home from vacation to find 110deg weather and a broken A/C. The thermostat kicks off the inside fan at the right temp, but the outside fan and compressor do not respond. The condenser test okay with amp meter (60+5) and was replaced two years ago. The contactor is good. The fuses are good. I installed a new thermostat a few weeks ago. To rule that out, I swapped in the old one but still no success.
I don't know where to go from here. I've contacted every heating and cooling company in town but have yet to get a reply (perhaps they aren't working weekends). If you can help me, please advise of next step. It's 109 today and at 10:30am, the house is already 95degrees.
Sounds like you have checked most of what I could think of....you have verified you are getting voltage out to the condenser, right? Is there a signal wire that runs out to the condenser to turn it on? Check that the signal is reaching the condenser to turn it on if there is, there should be a small wire that turns it on....from what I remember anyhow.
What brand and model c> I came home from vacation to find 110deg weather and a broken A/C. The
Sorry, I did mean capacitor (heat is getting to me). The guy at the appliance part store checked the capacitor measuring Ohms using multi-meter. The contactor is engaging when the thermostat kicks on the cooling process.
There are two wires coming into the air conditioning unit from the house (one red and one white). The white one shows 24V but the red wire shows zero volts. Should that have power?
No need to apologize. Condenser is another word for capacitor, but some people use that term for the compressor, which is why I asked. It can get confusing.
What the appliance store guy did is not a conclusive test by any stretch of the imagination. That said, the fact that he didn't try to sell you a replacement is a pretty good indication that he was convinced it was good.
So does the compressor hum when that happens? If it does, then the compressor is getting power. If it doesn't, then you have a circuit breaker tripped or something else wrong upstream.
Realize that there are several circuit breakers (or fuses) implicated. There's the side that protects the control circuitry and blower; that you have 24V at the contactor means that one is ok. The second (pair of, in most cases) breaker(s) in the main panel protects the compressor circuit. In some cases, there's a third set, in a sub-panel close to the compressor.
It would not surprise me if that second (or third) pair of breakers/fuses is tripped/blown.
That's the low voltage control that turns on the contactor. 24V is as expected when energized.
By testing ok with an ammeter, what do you mean? Did you actually measure amps, or was it volts or ohms? To measure amps you would need to take a wire off and put your ammeter in between the wire and where it was connected. I wouldn't do that.
I don't know specifically about in air conditioners, but in general it is insufficient to test a capacitor with just an ammeter, even if one could do so. You need to measure if the condensor is open and if it is shorted. I don't think your condensor is likely to be shorted.
What I would do is test the condensor in other ways (although I would do this after the parts below). With both circuit breakers off, (but I don't think you have to disconnect any wires from the cap) I would discharge the capacitor (same thing as condensor, you've said) with a screwdriver shank, from one lead to the other**. If you see a spark, it was charged and it is good.
If there is no spark, that doesn't mean it is bad, only that it wasn't charged. Then I would use a voltmeter to make sure it is fullly discharged. (If there was a spark but you still want to discharge it, apply the screwdriver a second time. It may well spark again.) After you think it is discharged, measure with a voltmeter (the voltmeter part of a multimeter usually) starting with some range that is 240 volts or higher, and going to lower ranges until the meter shows under
9 volts. Never use an ohmmeter until you have used a voltmeter first to make sure that no voltage is present which will damage the ohmmeter (even if it is the same meter with a switch that has been turned)
When the voltage is close to zero, you can then apply an ohmmeter to the same two contacts. With a meter that uses a meter, one can watch the ohmmeter fill the cap, so the resistance shows up as near zero at first and gradually climbs as the voltage in the cap pushes against the usually 9 volt battery that is in the meter. This is clear with a meter that uses a needle. The needle goes all the way to the right, then gradually back to the left again (high resistance). With a digital meter and a small capacitor, it's hard to see this happen, but with a big AC cap, you probably will be able to.
If there was no spark and the resistance always stays near zero, it would mean the capacitor was shorted, but I don't think that is possible in your ac. I think if it were shorted the 220 volts would burn out the cap, maybe making it swell or explode, or burn out a wire going to the cap. So, in other words, if your ohmmeter shows a low resistance, you don't have to wait until the resistance climbs (I don't know how long that would take in a cap this big (electrically, not physcially. 25 micro farads is enormous compared to caps used in electronics.)
**I don't think any damage can result from discharging by shorting from one lead to another, but someonee here may have more to say on that. Some caps have three contacts, because there are two caps in one can, sharing a common "neutral". Then you should be sure to discharge both halves of the cap before applying an ohmmeter.
But I would do all of this only after I do what is below.
Because it clicked? If that is all you know, that just means that the primary winding of the contactor is good and that the the armature, or whatever is supposed to move, moves freely. And that the 24 volt control voltage is present. To be sure the contactor is good, this you have to do with all the circuit breakers on: You have to turn the thermostat so that it calls for cooling and the contactor clicks ON, and then you have to use your voltmeter set on 240 volt scale or higher to meausure the output voltage of the contactor. 240 is a lot, so be especially careful that the meter leads don't touch what you don't intend them to, or that the one inch metal part of one lead doesn't touch two separate electrical contacts at the same time.
Make sure you're not measuring the 240 or 220 input voltage (well you can measure that to make sure that is there too, but to test the contactor you want that voltage connected to the output, the wires that go directly to the compressor.) But first look two paragraphs down to see how to tell just by listening to the compressor hum, if it does. (I'm only going in this order because you brought the topics up in this order.)
Frankly, I have a hard time looking at both probes at one time, so I replace one probe with an alligator clip, so I can clip it on, with the power off if I'm scared, and then I can concentrate on the one probe that is left. If the power is on, I make sure the alligator clip is covered in a plastic cover or that I'm wearing a glove. and that my other hand isn't touching something metal. This would be a little harder outside, especially when the electrical parts of the AC face a wall and there isn't much space in between.
But A) I would test the contactor like this only after I did what is below, and B) the other poster is right that if the compressor hums when the contactor engages the contactor is working.
Open the windows and dig out your fans. Have them blow directy at you. Learn to sleep without clothes and without sheets or blankets on top of you. Or sleep on the roof or in the yard.
What the other party said about there being 2 or 3 places the power could be off is the most important and what I would check FIRST.
If you have the 24 volts, then the fuse or breaker to your furnace or at least your AC control circuit and the thermostat is working. It's ON.
Then there may be another circuit breaker or fuse in the main fuse box that goes to the compressor outside. Make sure that is ON. Then I have another small circuit breaker box right on the wall outside next to compresssor. That tripped once, and after I reset it, it didn't trip again for years if ever.
Finally, you may have signed up for a discount from the power company for letting them turn off your compressor for an hour at a time. Maybe up to 2 hours and maybe they're picking on you and they made it longer than that. There's a grey plastic box on my compressor that indicates that I did that, but I forgot, and that might be why my AC didn't work for a couple hours or more after I first turned it on, on Tuesday.
When all these things are on, maybe the AC will work again.
you say your relay is kicking in ,so, if you have 110 going in and out of each leg of the relay,id try a capacitor.if that doesnt fix it, you may have bad compressor.lucas
Thanks for your help. Turned out to be a breaker that I didn't know existed. There are two breakers (linked together) in a box next to the meter. One of the breakers was tripped and had to be reset. I feel so silly that I didn't know about that. I had checked the main breaker panel and it was okay there.
I would suggest that unless you had a lightning storm around the time the breaker tripped that it might be a harbinger of things to come. You may have a problem developing. Preventive maintenance / a checkup might be in order. You can probably wait 'til a cool spell so you can get a better deal and quicker response from your favorite AC service firm, but a little attention soon might avoid an expensive repair later.
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