Air handler not working

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  #1  
Old 06-15-08, 08:39 PM
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Air handler not working

Hey everyone, hoping someone can help me diagnose why my blower ain't blowin!. I have a Carrier FK4CNF003 variable speed air handler unit that made a funny pop and stopped very quickly last night.

I have been having a few problems with the whole system recently and had the motor capacitor on the outside unit replaced last week. The system seems to have been running erratically (condenser fan running but not the compressor sometimes, sometimes fine) and I was going to call the service guy back but hadn't yet.

The air handler tripped its breaker twice in the past few days. These problems have been occurring only when it's really hot out. I'm in SE, VA and it's been pretty hot. So I reset the breaker and it would come back on until the pop sound happened. This time it did not trip the breaker, it just quit working. Nothing will run, not even the outside unit. No matter where I set the thermostat (cool or heat) I get nothing. Fan to ON does nothing. I even pulled off the thermostat and jumped the power to fan lead, still nothing. So I figured I'd take a look inside the air handler. Here's the rub, the air handler is under the house, the crawl space is about 24-28" high. The air handler sits on a few paver blocks. Yeah it's lame. I didn't do it, but I'd like to find the guy who did. Never the less, it is very difficult to get to and very difficult to service. It's in a very cramped space with a bunch of plumbing in the way. But, I got the cover off and looked inside. There's not too much in there really, a small pc board, a 24v transformer, and some heater strip parts, the blower assembly is separated by a metal plate. And a BUNCH of wires. There's a 5A fuse that's still good. And around 10 of the wires into two plugs that go to the motor. The motor is GE 230v 1/2hp.

So the big question is, how do I diagnose this thing? I'd sure like to take a crack at it myself (with some of your generous help, of course) because, heck - I don't think my A/C guy could even get under there! And I can't imagine what someone would charge for such filthy duty if they could fit. So where should I start? Should I focus on trying to test the board, the motor?, or the wiring? Is any of this test-able?

I pulled the blower unit out (its heavy) and the wheel only turned around once when I spun it. I would have thought it would spin a while if I gave it a good Wheel of Fortune type shove. I guess this might be an obvious thing but I don't really know, that's why I'm posting here. I sure hope it's not the whole motor because I looked it up online and it's almost $600 for the part. The pc board is nearly $200. And did I mention it's a ***** to get to? Anyway, that's it so far. I did take pictures of everything while I was under there so I do have some reference if that helps.

Any insight or guidance anyone can provide would be very much appreciated. The forecast is 92 degrees tomorrow. So thanks in advance!
 
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  #2  
Old 06-16-08, 05:29 PM
Jarredsdad's Avatar
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Location: Troy, VA
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Hey SE VA, I was in VaBch from 84 to 05.

What you have there in your Variable speed blower is really a 3 phase DC motor.

Since the fuse in the unit is good you can probably rule out the low voltage side.

The fact that the motor will only spin once isn't very good.

You need to have this tested by someone with the proper test equipment. Crotec (google that) electronics makes a great tester for both the motors and the control board. It's $200 - 250 from them or $600 from York.

Bottom line is someone has to get under there and test the motor.

Good news is, that if it is the control module (black, back part of the "motor") you can just change that and not the whole thing.
 
  #3  
Old 06-17-08, 01:33 PM
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Air handler

Thanks for the insight. After talking it over with a few local A/C guys (neither of which we're willing to work under the house), it's looking like a new air handler is the right way to go. And putting it IN the house not under. It will cost a few bucks and I'll lose a hall closet, but the best thing to do in the long run. Turns out the handler I have is not really a good match for the condenser unit I have anyway, hate to put any money into it.

Hopefully it won't take too long to get the new unit installed. Was mighty hot in the house yesterday. Thanks for taking the time to reply. I appreciate the cautions as well.
 
  #4  
Old 06-17-08, 02:14 PM
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That's why we stop by here Shipmate, glad to help.
 
  #5  
Old 06-17-08, 04:54 PM
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By the way, I'm a heating and cooling service tech, and as much as I might loathe accessing equipment, I see it as my job unless there's danger to it. And I don't charge more for a situation like yours. If I can't fir into the space, that's a different matter.

That said, putting the new system in the house instead of under, may have more benefit than you might realize. You might get better service. If there's an air filter at the air handler unit (as opposed to the return grille(s)) it will be much easier to replace when needed, which is important. And if you want to figure out things in the future, much easier and better access. If this was all obvious to you, sorry for wasting your time.
 
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