Air Conditioning - Hot air blowing

I am faced with exactly the same situation I had about 2 years ago. The downstairs unit works fine but the upstairs unit blows hot air.

I did the following steps so far.
1. I checked the incoming refrigerant line and the outgoing refrigerant line outside at the condensor. Outgoing line ( the insulated one) should be cold but it is not. Both the lines are almost at the same temperature with no perceptible difference.

2. The last time I had this problem I was able to trace it to a bad capacitor and was able to fix by replacing it. This time too I swapped the capacitors from the good unit to the bad unit and tried to determine if the capacitor made a difference, but swapping it did not make a difference.

3. The outside fan and the pump seem to work because I can see the fan running and hear the pump running as well.

When I was doing this the last time, one of the service technicians that I spoke to said that a bad capacitor could be an indication of a bad compressor. Could my compressor be damaged? is it possible to tell with out getting an HVAC technician come over to my house.

If I were to continue to run the upstairs unit ( since the upstairs gets cold after a long time with the cold air from downstairs circulating) with its current condition can it damage the compressor or any parts of the system?

What should by next steps be in investigation and diagnosis?
a) Is it low on Freon? how can I tell?
b) bad compressor.
c) Anything else that I should investigate?

Thanks in Advance.
Mallik

let just the fan upstairs run. You say the fan and compressor run outside .So next is get a tech to put gauges on it.

"3. The outside fan and the pump seem to work because I can see the fan running and hear the pump running as well."

And both lines are the same temp.

The big insulated line is suction (incoming) to the compressor. Sounds like you are short of refrigerant.

Call a tech. Let us know what is reported to keep you (hopefully) from being screwed.

Chris

My understanding is that the unit cannot be low on refrigerant unless there has been a leak. My unit is about 7 years old. Should I ask the tech to come and look for a leak or just check for low refrigerant and refill the line? Is there any thing else I can do before I call the tech?

Thanks,

like said . Did you feel the copper lines at the outdoor unit?? With it running. Is the big line cold and wet the small one warm to hot?

Tell the serviceperson what the symptoms are. Do not suggest any course of action on their part. Let them make the diagnosis and give you your options.

Ed, I checked both the lines while running. Normally the insulated line, would be cold and wet ( which is the case for the downstairs unit which is functioning properly) however both the incoming line and the outgoing line are same temperature and there is no condensation.

I may end up calling the tech ultimately, but I want to do my bit in diagnosing the problem to the extent possible.

You have done your bit. The next step is to attach guages to the unit. It is now time to call a tech.