Hi all, Any air con gurus out there? I have a Cat challenger 875c and have just replaced the compressor drier and TX valve. (Front seal of last compressor failed) after replacing the parts I vacuumed the system down and checked for any leaks. Once I knew the system was tight I put 2.2kg of r134a in it according to OEM stamp. Once working the tractor again the air started to feel warm. I put my gauges back on and found that when the compressor cut in, the high side went almost instantly to 400psi and cut back out again. It would stay cut out for 10-12 seconds then cut back in and go to 400psi again. This would keep repeating and the air was not cooling. The condenser is spotless and airflow through it seems to be good. Any ideas?
Whats your low side pressure and ambient temperature? Ive seen dryer bag split before sending desicate through system but thats worst case.
30psi when cut in 60psi when cut out Ambient temp is 39 degrees Celsius
Pressures are close, maybe a Little low on low side for 40c. I think it should be around 45 on low and 350 on high. Thinking tx sticking or blockage. its a bit sketchy, but maybe bridge cut switch and keep close eye on high side pressure see how high it gets. That will tell you if it over gassed or blocked.
Another thought, did the evaporator freeze up? Maybe the thermostat switch isnt reading or probe has come adrift!?
tx shouldn’t be blocked as it’s brand new. I bridged high pressure switch but gauge got to 450 and I plugged it back in. I’ve let a bit of gas out and it seems to have stabilised. High side is on 350psi and low side is on 20psi. The compressor is now engaged constantly Cab is much cooler now but I’m sure somethings still not right
When you switch on the compressor you say the high side goes to 400psi.When that happens what does the low side read? When you shut off the compressor do the pressures equalize within a minute or two? If you let out some refrigerant and it cools better than you either overcharged it, the stated capacity is wrong or you have too much oil. The oil takes up space. It is important to have he right amount of oil.
Don't see a Challenger 875C on the list anywhere. It stops at 865C. With a Serial Number I can check double-check the gas charge against the 2.2kg on the data plate.
Chart says low side normal, high side high, would indicate poor condenser flow or high side restriction. If the tx was clogged it should be pulling a vacuum on the low side. Was the compressor new or rebuilt?
Low side normal and high side high is usually an airflow concern, unless it is a variable displacement compressor.
If high side pressure spikes as clutch engages, there's a restriction or blockage. Why was the A/C system repaired in the first place? Don't allow yourself to fall into the trap of "new means good" but at the same time gotta find the root cause. I am unfamiliar with your configuration, where is the condenser located? By the engine fan or does it have its own stand alone electric fan?