freon pressure

[Tx Jim]

I'm curious as to what the high pressure is. Ambient temp affects what the highest high psi an ac system should operate efficiently. When I check my AC systems I pay more attention to the high pressure gauge than the low pressure gauge to determine if system has correct amt of freon.

 

[shaley]

I'd just add freon until the evap is cold with just the last tube flashing to vapor. About 10 deg superheat. Do you have a sight glass. You can't really tell freon level with gas pressures unless you have a charging chart for that particular system. Gas pressure is a function of its temperature.

 

[RickB]

Sorry. I was yeasty first thing this am. I was mainly wondering if the 40lbs was system pressure. Because no there is no magic number but I assure you if system press is 40 it is low

Maybe, maybe not. Have you ever seen a published specification for system static pressure?

 

[YesDeere]

No I have not. But having hooked my gauges up to everything from car/truck ac to tractors to carrier mobile units to house units I will just say it's a feel good thing.

 

[jake123]

the pressure is 90,engine off and 28 at 1500 rpm's, The temp is 58 in the vent.I only ran the motor for 10 minutes.At this pressure,curious if the evaporator would freeze up like it would it a vehicle.I guess I'll try and add more and watch the temp in the vent.I am like yes deere,been messing with adding,pulling vacuums,replacing expansion valves,orifice tubes,etc. Just kinda go by the seat of my pants. lol I did notice there was a good bit of oil that come out of the low fitting when i took off the guages.I know too much is not good.Maybe I should evacuate the system,pull vacuum and recharge?
i did wash the condenser lately,this makes a big difference.
Thanks for all the replies,definately different opinions lol

 

[RickB]

the pressure is 90,engine off and 28 at 1500 rpm's, The temp is 58 in the vent.I only ran the motor for 10 minutes.At this pressure,curious if the evaporator would freeze up like it would it a vehicle.I guess I'll try and add more and watch the temp in the vent.I am like yes deere,been messing with adding,pulling vacuums,replacing expansion valves,orifice tubes,etc. Just kinda go by the seat of my pants. lol I did notice there was a good bit of oil that come out of the low fitting when i took off the guages.I know too much is not good.Maybe I should evacuate the system,pull vacuum and recharge?
i did wash the condenser lately,this makes a big difference.
Thanks for all the replies,definately different opinions lol

28 psi low side pressure isn't all that far off. 58 degree vent temp doesn't tell us anything without knowing the ambient temp. My rule of thumb for tractor A/C systems is if I can get a 30 degree differential between ambient and vent temps, that's usually pretty good. Make certain that the heater control is shutting off the flow of coolant to the heater core. Pinch a heater hose off with needle nose visegrips or a hose clamping tool and see if the vent temp drops further. When the heater fights with the A/C, the heater wins EVERY time.

 

[jake123]

Well,it was about 88 outside when I checked it.I heard about the 30 degrees difference,I agree with that when it comes to central units and window units,but with car ac's I like to see at least 40-50 degrees with temp difference.Usually you have a temp reading around 38-45 degrees at the vent.I shut off the heater valve weeks ago.Low pressure flucturates with the outside temp,so I try to compensate for that.I still think I need more than 28 lbs.on the low side but not for sure.It's the first time I messed with a tractor.
I think my major problem is with all the glass on the cab,It's so hard to cool.
Maybe I need some blinds inside to open and close lol
Thanks for the reply,this is getting interesting
Alan

 

[YesDeere]

134a on any system is gonna run higher than 28 on an 88 degree day. Keep it at 1500 rpms and add some. Bleed the tank line(yellow) for at least two seconds. Then open it up. Keep a hand on the low side line and feel for the surges of cold. When there is no fluctuation in temp it's full. Doesn't need to be perfect just gd cold