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Heating / AC question (no AC)

Old 05-23-05, 10:38 PM
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Heating / AC question (no AC)

My central AC worked a week ago, then suddenly it stopped working.

My house is 18 years old, this is the original AC unit (or whatever it's called, that box outside the house). I looked at it and cleaned out a couple of mouse nests, and found an owners manual in it. In the owner's manual it mentioned that it needs to be oiled every five years... I'm pretty sure that this has never been done. I cleaned out the crud, fiddled with the wires and connections, but it still doesn't work.

If it's not that, it could be my thermostat. It's one of those older ones with a mercury vial inside, when I turn on the heat I see a spark when I fiddle with the temperature, when I turn on the AC I don't see anything.

I'll be calling a heating/AC company to come out and look at it in a few weeks when I'm working on my roof (new shingles) so I know I'll be home when they come, but in the meantime, any ideas? Can a bad thermostat cause the AC to not work?

I'm interested in changing my furnace / AC unit, but I was hoping to get another year out of it. I'm spending ~ $2,300* on my roof in June, and I just spent another $2,100 for my wife and kids to go to South America to visit her family, things are a little tight.

Thanks!

Oh, and if you own a house, open your outdoor unit sometime. There'll most likely be the owner's manual inside, you might need to have it oiled periodically...

* that includes $500 for a compressor and a Bostitch roofing nailer which I'll have after the job is done

Last edited by Heat; 05-23-05 at 10:40 PM.
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Old 05-23-05, 10:54 PM
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You're probaby looking at another $2500 and up for a new furnace and AC unit, depending on the size of your house. Is it possible to get a home equity line? That's what we used to remodel last year.
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Old 05-23-05, 10:54 PM
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Probably not a thermostat. Your unit is most likely a heat pump, unless you have a gas furnace.

Crap, scratch that. If it were, it probably wouldn't break like this. Most likely a compressor or it needs freon.

One would think that just being a little low on freon would just make it cool slower, but it doesn't. All or nothing, typically.

Does the unit outside even come on?
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Old 05-24-05, 12:01 AM
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Welcome to my world... my condenser (outside unit) blew a capacitor which caused an arc into the frame when I tried to reset the breaker (before knowing about the blown capacitor) punctured a hole in the refrigerent line.. ~ $500 to repair but it is over 11 years old so looking at replacing the whole system.... ~$5500 . Seems damn high to me, but another quote I got was ~$7200.

Does the inside unit (blower) come on ?? if it does and is not cooling check for a tripped breaker to the condenser unit.. if neither is coming on then something inside is the problem.
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Old 05-24-05, 12:09 AM
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I have a gas furnace.

When I turn the fan on through the thermostat (the blower?), it turns on, but the outside unit remains off (and remains off no matter what I do, it doesn't turn on at all).

When you say to check for a tripped breaker, where would it be? I looked in my circuit box but nothing was flipped.

My house isn't too big (~ 1,700 square feet, a bileval).
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Old 05-24-05, 12:14 AM
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Thermostats are cheap, even really nice modern programmable ones. I would try replacing it, it is a very simple job. You can spend $30 and either fix it, or rule it out as a suspect in the problem. Even if it is not the cause, you should upgrade it anyway.

Sounds like the unit is not getting power, or not getting the switch that tells it to run. First look to the most common/cheapest fix, the thermostat.
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Old 05-24-05, 01:47 AM
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Originally Posted by Heat
I have a gas furnace.

When I turn the fan on through the thermostat (the blower?), it turns on, but the outside unit remains off (and remains off no matter what I do, it doesn't turn on at all).

When you say to check for a tripped breaker, where would it be? I looked in my circuit box but nothing was flipped.

My house isn't too big (~ 1,700 square feet, a bileval).
The outside unit should NOT come on when you turn on the heat, only when you turn on the A/C.... when you turn on the A/C and turn the setting down low enough for it to come on, does the inside blower come on ?? If not then it may be the thermostat... if the inside blower comes on but not the outside condenser then it is a tripped or blown circuit. My breaker is inside the normal breaker box, but your house is a bit older so it may be somewhere else... there should also be a breaker/fuse/safety lockout somewhere near the condenser outside, don't know if that may be the problem.

At 18 years old though it probably is time for a new system... most things I have read say ~15 is average life... of course your results will vary.
It also sucked I paid $85 for the service guy to come out and tell me what I already knew.
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Old 05-24-05, 06:35 AM
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IIRC, the most common problem with AC units that exhibit these symptoms is the startup capacitor (called the ballast or booster by different AC repair dudes). When the external AC unit turns on it has to kick over and run the compressor. This is a pretty hard task for that little compressor motor, so there is a startup capacitor to give it enough juice to get it going. Capacitors just go bad, and even fail energetically (I have had 2 blow so hard they visibly dented the housing of the unit, look at what happened to greg9x). But as mentioned here it could be many other things. IF it is just the capacitor, you're probably looking at a couple hundred dollars to have a fella come out and fix it. Like greg9x said, it would probably be best to bite the bullet and replace the unit. The energy savings you would get from a newer more efficient system will help ease your financial pain, as will the cold air coming out of the vents.
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Old 05-24-05, 10:57 PM
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Originally Posted by RandyC
...First look to the most common/cheapest fix, the thermostat.
Reminds me of a time about ten years ago when I had electrical problems with my car, I took out the alternator and had it tested, it was fine, had a b**** of a time getting it back in (dang serpentine belt). Then I realized that the battery was, in fact, dead, something I should have checked first.

Anyway, I happened to have two older mercury vial style thermometers at my work, I was waiting for a mercury recyling event to drop them off. Today I took the better one (a rectangular Honeywell one) and installed it.

I have cold air again! The condensor (the outdoor box) is running, cold air coming out of the vents, things are fine. I'll replace the thermostat with a modern one in a couple of weeks once my wife leaves, and I'll also have somebody come out to do maintenance (oil only, or something else?) on my condensor. Like I said above, I just realized that the manual said to oil it every five years; it's 18 years old now and it's most likely never been oiled.
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Old 05-24-05, 11:24 PM
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Fantastic. I was actually surprised no one recommended changing your user name. That was my next suggestion.
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