Compressor Running - No Cooling Trane XR11

[bigjoncoop]

Quick Summary:

CONDENSER: Trane XR11
SYMPTOM: Not Cooling
TROUBLESHOOTING STEPS: Replaced 55MFD Cap

Conclusion: After replacing the capacitor found out that was not the issue. Upon inspecting the compressor found that the compressor was not overheating and seems to be running perfectly fine and sounds healthy. (No  bad noises or humming) Also the compressor continues to run and the low pressure switch is not being tripped. So both the compressor and fan sound perfectly fine and seem to be working like normal. The condenser is just not cooling for some reason...


FULL DETAILS:

So I get to my brother's yesterday to washing dogs and the house is a 81° and the thermostat is calling for cooling...

After making sure that everything seemed  to be running correctly, I Ran and got a  new 55-7.5 MFD capacitor, since the out door condenser is pretty old...

After replacing the capacitor the unit was still not the cooling. So my next thought was the compressor most likely needs to be replaced but maybe throwing a hard start on it it would help for a while.

So I wanted to verify that indeed the compressor was not kicking on etc...  So I opened the unit up to see it the compressor was burning hot and to my surprise it was barely hot at all. So I then disconnected the fan to verify what the compressor was actually doing, and come to find out the compressor sounds like it's running perfectly fine and doesn't make any strange noises or "hums", etc... It kicks on immediately as it should.

I reconnected the fan and turned the unit back on and I can hear the compressor running and it does not turn off. The unit has a low pressure cut off switch but the unit continues to run like normal but just has zero Cooling.

Unfortunately I don't have my gauges with me to verify the refrigerant pressure. I think my next step might be to trip the pressure switch manually and see if the compressor turns off to verify the low pressure cut off switch is working properly

[Sergroum]

How would you trip the low pressure switch manually? Pulling wires won't be correct. If the sensor is stuck in closed position, pulling wire, or checking continuity won't do it.

There are some things you can to guesstimate and provoke things, but honestly just get the gauges.

aside that.

What is the approach temperature? Ambient temp of the air and the air coming out from the top of the condenser outside.

What is the temperature of the refrigerant pipes coming into and out of the condenser?

Is the liquid line significantly hot, or are both pipes roughly the same temp?

[bigjoncoop]

What is the approach temperature? Ambient temp of the air and the air coming out from the top of the condenser outside.

What is the temperature of the refrigerant pipes coming into and out of the condenser?

Is the liquid line significantly hot, or are both pipes roughly the same temp?

I don't have my temperature gun with me but...

1. The air coming out of the top of the unit is basically unchanged.

2. Both pipes feel exactly the same temperature. No difference at all. There is no change in temp of either pipe after turning on the unit.

It seems as if the compressor isn't running...

***Not sure if this is useful but my brother just told me that since he bought the house about 6 months ago, normally when the air conditioner kicked off, the outside unit after 20 seconds or so would briefly sound like a "whining dead duck". I can confirm that it does not do that now.***

[Sergroum]

I wouldn't go past this point without checking pressure.

You say the compressor is making some kind of noise, so I guess it's getting correct power and isn't tripped out on thermal overload, or any other sensor. 

it's either very low on gas pressure, or compressor is not compressing.

[rmuntz]

Call a professional