Trane XR12 not blowing cold air


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Old 05-26-16, 01:42 PM
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Trane XR12 not blowing cold air

I've got an older Trane XR12 (2003) unit which I just switched over to cool and it won't blow cold air. This is the upstairs unit and it worked fine last season. The downstairs unit still works fine.

The unit appears to work properly but won't chill. The capacitor was replaced 2 years ago and looks good. The fan turns fine and I can hear the compressor running. I checked the leads from the compressor and they're not open.

The refrigerant line stays the ambient temperature whereas the downstairs unit the refrigerant line, as expected, gets very cold.

At this point it sounds to me like the unit lost it's charge somehow but if I've overlooked something I'd like to avoid the service call I've got scheduled so any suggestions of where to look next are welcome.
 
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Old 05-26-16, 02:07 PM
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If the compressor and fan are running most likely it's low on refrigerant. Make sure you shut it down don't let it run like that.
 
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Old 05-26-16, 02:21 PM
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I've got it off for now unless someone comes up with another idea.
 
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Old 05-26-16, 02:55 PM
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On a Trane unit.... if you are low on refrigerant the condensor wouldn't be running. Either the compressor is not running and sounds like it is or someone bypassed the low pressure switch.

If the compressor is indeed running.... the compressor would have to be internally damaged.
 
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Old 05-26-16, 03:10 PM
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The top of the compressor was warm after running a bit and it does sound like it's operating. Though it's a bit tough to tell over the fan noise. I guess I could compare the sound to the know good unit to see if it's the same.
 
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Old 05-26-16, 03:16 PM
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If you have the condensor apart..... disconnect one of the fan wires.
That would make it easier to hear the compressor.

All the typical warnings apply.... turn off power while opening unit. Be advised you are working with 240vac....... etc.
 
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Old 05-26-16, 04:44 PM
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Did as suggested and the compressor definitely makes noise so I assume it's running. Seems a bit loud but not sure how loud it is normally.
 
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Old 05-26-16, 04:48 PM
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If the compressor is running then the low pressure switch was bypassed or the compressor is internally damaged.
 
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Old 05-26-16, 04:56 PM
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As far as I know nothing has been bypassed. I really hope it's not a bad compressor as I can't afford a replacement at this time.

I believe the only work that's been done on these condensers has been to replace the fan motors and the capacitors. Both units failed about 4 years ago a couple of months apart. Seemed really odd at the time. I was the one that did the work and they've worked fine since that repair.

ETA: I looked and don't see any sort of a switch in the refrigerant line and the only wires coming from the inside of the unit are for the motor. Would it be somewhere else?
 

Last edited by T Morris; 05-26-16 at 05:25 PM.
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Old 05-26-16, 06:08 PM
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Is this a heat pump? If so sometimes the reversing valve can stick, just change it from cool back to heat and let it run just a few minutes then cut it off and then start it back up in cool. Pretty small chance this will work but I would try it before making a call...... most likely the unit is refrigerant challenged.
 
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Old 05-27-16, 03:41 AM
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No joy on switching modes.

One other thing I just remembered is that at the end of last season there was water in the catch tray of the air handler for this unit. I know that's not good and I knew I was going to have to deal with it come springtime. I'm guessing this is all related.
 
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Old 05-27-16, 10:41 AM
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Water in the condensate pan usually means a clogged drain tube. Although it's not good to leave the water in there as it can rust it usually doesn't cause your problem unless the coil was also sitting in the water and corroded thru.
 
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Old 05-27-16, 01:48 PM
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Well, the bad news is the system has a leak and the line had zero charge. I had it pressurized with ~100 lbs of nitrogen and it lost about a pound per minute. With those results it's an expensive proposition no matter whether I opt to fix or replace.

Based on my research the cheapest a replacement coil for the air handler would be is a grand or more depending on the source and that doesn't include the labor to do the R&R. The other option is to track down the leak(s) and fix them and that runs about $500+. Recharging the system with R22 is about the same as finding the leak.

I've got a meeting scheduled for next week to discuss replacement options for installing a new unit and will decide once I know the prices.

Too bad cold air doesn't rise At least the basement and main floor will be cool.
 
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Old 06-01-16, 07:13 AM
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It looks like a 2.5 ton Carrier unit will run about $6K installed which is more than I can afford at the moment. Based on this I'm going to look into doing a repair as we'll be selling the house in a couple of years and likely won't recoup the cost of the new unit in that period.
 
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Old 06-09-16, 06:34 AM
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Final update:

The leak was located at the on of the pipes at the heat pump. Thankfully it wasn't any of the coils as that would have been much more costly and probably led to a full system replacement. The tech did sniff around the coil in the air handler and came up totally blank so that at least looks solid for now. We did replace the drier as there was concern over contamination so that added to the overall cost. I don't know if that was totally necessary or not but it did sound somewhat reasonable.

Total cost of parts, R22, labor, etc. came to just under $2K so not cheap but 1/3 the cost of a full replacement. As long as the system can hang on for another 3 years or until we sell, I'm good with that.
 
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Old 07-07-16, 05:30 AM
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Well, the saga continues.

The repaired unit was running for about a month before blowing warm air again. The unit still has refrigerant and the pressure is fine so the tech is suggesting that there's a valve that's not opening to allow the refrigerant to flow when requested. The theory is that something (contaminants, water vapor,???) got into the system since it's not know how long the system was in an "open" state before repair of the leak.

I've cycled the unit on/off multiple times to try and free up whatever is stuck but no luck. Any other suggestions would be welcomed as parts replacement would be another $1500-$2000 on top of what was already spent so that doesn't make any sense. A replacement system is going to run ~$6K but they're going to see if we can at least get some sort of credit back on the labor for the earlier repair. We'll still be out the cost of the R22 so that really hurts.
 
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Old 07-07-16, 10:24 AM
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If there is contaminants or water vapor in the system then he did a crappy job. I will cut him some slack on the leaks, sometimes they are a nightmare to find.
 
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Old 07-07-16, 11:23 AM
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I think what he was saying is that the damage may have been done prior to any repair/purge/refill - though I'm not positive about that.
 
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Old 07-08-16, 05:53 PM
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There are a lot less costly replacement refrigerants for R-22 & they pass EPA standards.

Then R-22 should have been recovered & the lines blown out with nitrogen with all leaks repaired a double or triple system evacuation would have gotten rid of any contaminate problems.

Then you recharge with MO 99 or another compatible replacement refrigerant. End of troubles...
 
 

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