Now the compressor doesn't appear to be running...

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Old 06-07-12, 07:42 PM
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Now the compressor doesn't appear to be running...

First time poster on this board. Thanks in advance for any help you can provide. Sorry for the long post. Way too much drama...

My family moved into a 24 year old house here in Austin, TX on 12/28/10. The downstairs Carrier AC/Heat pump was replaced in September 2010. Two weeks ago the inside blower motor stopped running when I wasn't home (I work in San Antonio Monday to Thursday). My wife told me the AC wasn't working and I quickly saw that the coils were frosted over as were the pipes in the compressor outside even as the fan was blowing. I turned everything off and quickly figured out the blower motor had failed.

This Carrier furnace has a Genteq X13 3 phase 1/2 hp DC motor. So when I looked for a capacitor I didn't find one. Rather, it has a control board built into the back end of the motor. The motor came with a 10 year warranty (parts only) so I called a local HVAC contractor and they told me that they had to come out and diagnose the problem even though I had already pulled the motor, tested the windings and found them fine, and figured out it was the control board and likely a blown thermistor (not accessible from the backside of the small board due to some stuff they melt into the area to keep moisture and do-it-yourselfers out). The repair guy came out while I was at work and the next thing you know they had charged me $180 to tell me the motor was backorderd for three weeks and the only quick option was to pull a motor from a new unit at their distributors. They would charge me for the trip to the distributor, pulling the motor, bringing it to my house, installing it at my house, at a later date when the motor came in they would charge me for another trip to the distributor and the time it took to install the new motor into the donor furnace. And did I forget to mention they would charge me to fill out the warranty information? Needless to say, we had no AC on the ground floor for Memorial Day weekend or that following week.

Faced with this annoying situation, I looked on Ebay and won a used Genteq X13 3 Phase 3/4 hp motor for $11.50. When I first installed it last Saturday the air was blowing backwards! I learned that I could switch two leads and the rotation would reverse which it did. Everything seemed to be working and I went out of town this week for work. I got back this evening and found the AC wasn't cooling even as the furnace blower was working fine.

I went outside and the compressor fan wasn't running. There was an electric humming noise. Sure enough, when I manually spun the fan blade the motor ran. I wasn't sure if the motor was going full speed or not. I went inside hoping that the refrigerant would flow but after 15 minutes the copper pipe still wasn't cold. Looking closely at the dual run capacitor on the compressor I didn't see any bursting or obvious defects. While trying the manual way of starting the fan I did notice a second electric hum noise, after a couple minutes of the fan blowing, that went on for a couple seconds before clicking off. And now I'm not sure what the problem is, but I am very frustrated at this latest turn of events. I'm thinking that I should go ahead and try to replace the dual run capacitor before calling in the pros once again. Whatever I do, it needs to happen tomorrow or my poor family will be without downstairs AC for another week if I don't pay another eye tooth for a service call. :-(

Any advice on what is going wrong with my 20 month old Carrier?

Thanks,
Trevor

P.S. The one piece of value add that the HVAC tech provided was sharing that the return grilles for our 3 ton unit were undersized and that is likely what caused the motor to go so quickly.
 
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Old 06-07-12, 08:21 PM
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replace the dual-run capacitor. Are the outdoor coils dirty?
 
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Old 06-11-12, 02:46 AM
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6/101/12 Update.

hvactechfw was absolutely correct that the capacitor was shot. I replaced it on Friday and now both the compressor and fan work. Unfortunately, the coils are frosting up and so are the pipes and compressor piping in the outside unit. This is happening even after I added return air volume by adding a 10" by 7" hole through a wall and directly into the return plenum.

I didn't notice the frosting over on Saturday after I switched the capacitor but that day wasn't as hot as Sunday. Basically, the unit starts no problem but quickly becomes ineffective at cooling because everything freezes over.

My thinking is that I haven't solved the root cause of the problem. I'm now thinking that the problem is that I'm low on refrigerant, there is blockage in the refrigerant lines, or there is still not enough air moving across the coils to keep them warm. With the extra air intake I can't understand why the unit isn't working properly. Cold air is coming out the registers even if it doesn't feel like a whole bunch. Is there a way to increase the motor rpms so more air blows? Right now the blue lead is on speed tap 2 and the white lead is on speed tap 4. Is it possible that the airflow after the coils has gotten blocked? The ductworks is between floors so I can't understand how it would get changed.

Thanks in advance for your continued help. This ordeal is wearing on me.

Regards,
Trevor

P.S. On the bright side after repeatedly calmly explaining my frustration in the solution offered by contractor#1 he has contacted the local Robert Madden distributor and somehow found a Genteq X13 motor that I can go and swap out myself so I don't have to pay a bunch more in labor fees.



Is it time to have another contractor out to check the refrigerant level and
 
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Old 06-23-12, 03:27 AM
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Eureka. I figured out the problem. The condensation drain line was mostly clogged. The unit has a kill switch that only turns off the blower motor. Thereafter, the compressor would continue running until everything froze up. I'm pretty sure that my wife would likely turn down the thermostat farther at first rather than realize something was broken. We have a zoned system, so the upstairs unit would keep it from getting crazy hot downstairs.

Presumably, with the system frozen up, each evening as the temperatures dropped everything would melt and the condensation would eventually thaw and drain and the AC would be ready to try again, and eventually seize up again. This must have played out for a few days in a row to the point where the blower motor and then the outdoor capacitor failed. Once, it got hot enough outdoors for long enough, it became apparent what was going on. And this explains why replacing the blower motor alone wasn't enough to make everything work properly when the next hot day came along.

The good news is that everything is working now that I have cleared the drain line sufficiently. Thanks for all the assistance from this forum.

Regards and feeling cooler,
Trevor in Austin, TX
 
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Old 06-23-12, 06:35 AM
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The switch is not wired properly if it only shuts off the blower. It should open the R circuit when tripped.
 
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Old 12-31-12, 12:12 PM
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"I looked on Ebay and won a used Genteq X13 3 Phase 3/4 hp motor for $11.50. When I first installed it last Saturday the air was blowing backwards! I learned that I could switch two leads and the rotation would reverse which it did."

Can you tell me what wires you switched to reverse rotation? I'm in the same boat I bought an x13 motor off of ebay that is reversible but I don't know which wires to switch to get it to reverse rotation. Please help me!! Thanks



 
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Old 01-01-13, 10:36 AM
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Sandra,

I don't recall exactly, but I'm pretty sure you switch the two power leads labeled "L" and "N". Have a look at this page to learn more -> How do I Reverse the Direction of a Residential Furnace Motor? | eHow.com.

And please do your homework to make sure I'm correct. I would hate for you to damage your new motor.

Regards,
Trevor

P.S. I spent 20 minutes trying to find my notes and or a web page that speaks specifically to the required fix.
 
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