A/C servicing.

[RPW]

I have a 2004 5520 and about to replace the expansion valve. Freon has already been recovered. Anything to watch out for? Special tools? I have the parts on hand (valve, receiver/dryer, o-rings).

 

[AWSubie]

It sounds like you're familiar with A/C work so I'll skip the common stuff and get to what has saved me money and grief over the years. If you have any soldering to do make sure you are running dry nitrogen through the system as you solder (google this to see what happens when you don't). Once you get the system together pressurize with dry nitrogen to check for leaks (yes you could evacuate the system and wait to see if it holds the vacuum but my experience is that if you do have a leak it is much easier to find with the system pressurized.

 

[RPW]

Luckily no soldering. No nitrogen either. No I just haven't had time to really look closely at the bolts that holds the tubes to the valve yet. On the surface it looks like just a plate that holds a compression fitting but it looks strange as it appears that the bolts screw into the plate AND the valve body. I'll take a closer look at the parts diagram. Thanks.

 

[R134a]

Just take a look at total system oil and guesstimate the amount of oil to add back w/the new drier. (It will be a small amount). Pull deep vacuum using a real pump. Special tools... a refrigerant scale will allow you to put the correct charge in. Mobile a/c is always charged by weight. You will do fine.

 

[RPW]

Just take a look at total system oil and guesstimate the amount of oil to add back w/the new drier. (It will be a small amount). Pull deep vacuum using a real pump. Special tools... a refrigerant scale will allow you to put the correct charge in. Mobile a/c is always charged by weight. You will do fine.

Well after all the work I'm back to square one. Have one more check before ordering a new compressor. Low side pressure is spot on but high side is low.

 

[Kyle_in_Tex]

Well after all the work I'm back to square one. Have one more check before ordering a new compressor. Low side pressure is spot on but high side is low.

Cab with no AC is not fun in summer heat. Hope you get it fixed.

 

[R134a]

How low is low ? A starting point is typically ambient x 2.2~2.5 in F. (for high side) assuming the charge is correct. *** Did the compressor fail ? Why did it fail ?
If i"m in to it, I look at an oil sample. Is it metallic / dark / discolored / contaminated ? If so, compressor likely circulated trash through the system including your txv . Evap core and lines should be flushed individually. Any muffler (if present) can't be flushed. Condenser can be pulse flushed with specialized equipment but not worth the investment unless you do this often. So you will be buying a condenser too. You have to be SURE all solvent is out before charging. Unfortunately no free lunch here. Taking short cuts usually results in the new compressor failing in a few months. Parts and labor... you can see why a/c costs $$$. 1234yf (the new refrigerant is worse) :banghead:

 

[Tx Jim]

Well after all the work I'm back to square one. Have one more check before ordering a new compressor. Low side pressure is spot on but high side is low.

Do you know how many oz's of refrigerant was in tractor's AC system when you measured low "high pressure"?

 

[RPW]

After all said and done problem found, it's a defective heat control valve. Seems it has been missed in prior diagnosis. Clamped off the heater hoses and temp dropped immediately. It bites that I spent so much time and money on the AC side when if I would have continued to check the rest of the system. Now to spend another hundred dollars on a valve.

 

[Tx Jim]

I'm glad you discovered AC problem. Why not install a $10.39 manual cut-off valve in heater hose similar to the way I did in '93 on my JD 4255. I've never opened the valve since I closed it as I have to run AC on low in my Texas Winter temp's.