6603 heat a/c question

[pnhigg]

I have a 6603 that I am having issue with the a/c. Tractor has 12xx hours
I bought the tractor used (auction) and the previous owne, said they had changed the expansion valve and dryer, but did not know of any other service to the a/c system.
The tractor cools very good at idle, but at higher rpm the system freezes up. I suspected the system to either have air flow issues or be low on refrigerant, but the filters, condenser and evaporator were clean. I hooked gauges up, and to get the low pressure up to anything higher than 20 the high side was 400+ and climbing.
I am certianly not an a/c expert, but it doesn't follow what I have seen in the past. Could it be an issue where too much oil is in the system causing the high side pressures to run too high.

Also was using the tractor yesterday, and the outside temp was 45*. I got a little warm in the cab so I turned the heat all the way down, and the just ran the fan thinking the fan would blow cool air from outside, but with the temp turned all the way down, and the fan on (no a/c) the vents were blowing warm air. I could turn the heat up and the it got hotter, but it never blew cool air as I would have expected given the outside temp.

I am wondering if I have a couple issues.

Thanks for any help you may have to offer.
Patrick

 

[Tx Jim]

I think it either has too much Freon(common problem) or condenser is plugged blocking air flow. Looking clean & really being clean are 2 different things. Down here in sunny Texas if the sun is shining AC needs to work. I've seen some heater water control valves that let enough water pass to affect ac cooling capabilities. My 4255 had the valve leakage problem so I installed manual cut-off valves in the heater hoses.

 

[Harry in Ky]

An external heater shut off valve is a trick I've used for years to combat a defective valve in the cab, but only one is needed. As for the A/C issue; What exactly, do you mean by "the system freezes up"? You said it cools OK at an idle. If so, what are the pressure readings at that point? If you have doubts about the condensor's effectiveness, get the system running and try using a garden hose to cool down the condensor while watching the gauges. If that drops the high side down considerably(to 250 PSI or less), you need to verify the airflow through the condensor and radiator. One or the other may not be as clean as it looks. If nothing changes, or at least not much, then consider the freon level, oil level, or even the performance of the new expansion valve.

 

[pnhigg]

Thanks guys.
I can add the cut off. I didn't even think of that, but we have them on both of Dad's tractors.
I will check again for cleanliness.

Harry, do you do a/c service? I am in Lexington and don't know a good a/c man

thanks again for the help