Air conditioning on 2-110 White, Cold enough?

I've got a 2-110 in the shop that the customer said had been worked on several years ago but had never worked very well and now has not worked for a couple years. It has been converted to R134A with a Sanden compressor. The evaporator and heater core have been replaced with the one piece unit and block style expansion valve like the newer tractors.

The system appeared to be low on refrigerant but did have enough in it the compressor was running. The low side would drop into a vacuum condition and the high side would run at less than 100 psi. After adding refrigerant I was able to get the low side stable at 4 psi and the high side at 190 psi. Ambient temperature was about 78°F. Outlet temperature in the cab never got less than 60°F. I have cleaned the cab filter and have good airflow through the evaporator. Low side hose gets some frost on it at the expansion valve but not at the compressor.

My question is, is this the best performance this system can deliver or is there a problem I am overlooking?

Hi Owen you have maybe checked this already but make sure you turn the hot water off at the block for heater core. Also I have run across this that the last time it was worked on they put in to much oil in the lines and it slugs the expansion valve. I think maybe drain the system flush,new drier,new valve, evacuate it for a couple hours then refill. It might seem like alot but then you know it was done right. Good luck I hope this helps Bob

My general rule of thumb for cold enough is close to 40. But shutting off the heater lines is good idea. Where are you checking the temp at? it should make 40ish right out of the vents. Could be the control switch is bad. When you watch your gauges the high side should climb relatively fast when the compressor kicks on and should stay on for a long time when ac is on full blast. If it turns on and off fast the switch is bad. Make sure your blower box is sealed good. It might have a few cracks or holes sitting that long. Also if you can stick your thermometer right in the evaporator in the blower box that will tell you a lot.. It should read no colder then 34-38. If it freezes it has too much refrigerant. The low side side should never be above 100psi and should never spike. When the compressor kicks off the high side should fall down to equal the low side. Hope these checks help ya.

When the AC guy recharged my truck this spring, he told me that low 60's was normal for an R134A system.

The low side pressure should be a lot higher than 4 psi more like somewhere in the 30's and high side probably more like high 200's are you sure you have enough in it

Like they said above. There may be to much oil in the system. I have seen this many times. I had one recently on our Volvo A-25 haul truck. SO much that it filled the dryer/accumulator full and was causing a blockage in the system. I had a vacuum on the low side and really high pressure on the high side. My suggestion would be to replace the accumulator and dryer. Flush out the system or get a good evacuator on it as it will take the oil out of it. Put a good vacuum on it for a couple of hours and then shut the gauges off and then shut the vacuum pump off and see if it holds the vacuum for an hour. If it drops at all there is a leak somewhere. If no leaks recharge it. When I recharge the equipment I take care of here at work I always look up the system capacity and use a set of scales to put in exactly how many LBS of R-134A it calls for. This seems to be the best route in getting them charged right. Remember more is not better with R-134A. Its not like the R-12 where you can squeeze in some more and make it colder it will go back to blowing hot air. When they are charged right you should have between 20-29 on the low side and anywhere around 200 on the high side. I have heard a 25 degree drop in the cab compared to the outside temp is good. Good luck.