I am getting a Low Pressure Switch Open fault on my Carrier Heat Pump. I previously had a problem with the unit icing over during the winter. The technician added a lb of Puron (and charged $120 for 1 lb?? ) and said everything looked OK. Is it most likely they missed something or is this just a strange coincidence?

If it was icing over in the winter, most likely was a problem with it not defrosting properly. 410a is only about 15 dollars a pound so that sounds like a huge ripoff. If you are getting a low pressure code the you are either low on freon again or the switch is not working correctly. Or there may be a restriction in the line somewhere. How old is this unit?

If refrigerant needed to be added last winter and the leak was not repaired then you will probably be low on refrigerant again. A good service person would have found the leak in your system and repaired it. By just adding refrigerant with no leak repair it will leak out again and again until the leak is repaired. This could get very expensive over time. You may try looking around the system for oil deposits since oil is one of the most common indicators of a refrigerant leak.

if it was icing over in the winter, most likely was a probelm with it not defrosting properly. 410a is only about 15 dollars a pound so that sounds like a huge ripoff. If you are getting a low pressure code the you are either low on freon again or the switch is not working correctly. or there may be a restriction in the line somewhere. How old is this unit?

The unit is only 4 yrs old. They fixed a leak by the accumulator about 2 yrs ago. The unit froze over this winter but they said everything looked OK maybe just slightly low on 410a. They said they fixed a loose schraeder pin and replaced a plastic cap with a brass one. I looked and from what I can tell is that one of the shraeder valves is missing a cap right now. I will check for oil to see if there might be any leaks later today. A 4 yr old system shouldn't be having all these issues IMO... frustrating.

A 4 yr old system should still be under warranty. Was the leak in the pipe to the accumulator or the accumulator itself was replaced. It is possible for the unit to leak from the shraeder valves expecally on the little line.

Joshdta is correct about the schrader valve leak. Just a small steady amount of leakage will cause a large loss in a short time. I always replace any plastic schrader caps with brass ones and always check to be sure the seal is in the new brass cap.

Some info on George Schrader.

Schrader USA - The Schrader Valve (http://www.schrader-bridgeport.com/index.php?option=com_content&task=view&id=59&Itemid=125)

Joshdta is correct about the schrader valve leak. Just a small steady amount of leakage will cause a large loss in a short time. I always replace any plastic schrader caps with brass ones and always check to be sure the seal is in the new brass cap.

Some info on George Schrader.

Schrader USA - The Schrader Valve (http://www.schrader-bridgeport.com/index.php?option=com_content&task=view&id=59&Itemid=125)

One quick thought. Do you think it could be a bad reversing valve? This would explain why during the winter it didn't defrost and why its not cooling during now? This was the first time I turned on Cooling and got the low pressure sensor open fault. I am sure they will check the pressure first but just was thinking what other possibilities it could be.

The warranty looks like it was 1 yr for work/installation and then 5 yrs for parts and 10 yrs for compressor. So I guess that's why they charged me for the small recharge. Is this fair?