A/C Expansion Valve Replacement

[Meezy237]

I replaced condenser compressor drier & high pressure switch also on/off switch on high side before I changed out switches mobile mechanic added jumper to compressor while charging it started cooling recommend I changed out both switches I changed those after a few days but still not cooling so I’m going to replace the expansion valve which I was told by another mechanic that it should have been replaced when I changed out majority of the system…when I vacuum system will I need to add oil back into the system or it should be fine ?

[Joey Mack]

What are you using to recover the freon? 

[Geoff Weeks]

Hold on! while it is possible that the Tx valve could have a problem, given what you have said so far, I would find it highly unlikely.

When I started doing A/C work, I also heard that maxim to replace the Tx when the system is opened. Experience has taught me different. I have NEVER had a Tx fail other than mechanically. In other words, the fitting or tube connection fail, and a easily inspected without removing.

I have seen far more damage done when people try to replace it for no other reason than "the book tells me to when I open the system".

I ran some experiments on my own systems, and found that in most cases (all I had) that replacement wasn't necessary.

 You can tell when they are bad via pressure readings  and "superheat" measurements. Given what you have stated so far, the chances the problem is the Tx are much less than 2%.

So lets address your problem and diagnose the system. Did you add the correct amount of refrigerant by weight? When you replaced all that stuff, did you add enough oil to the system?  What are the pressures now, both static and running pressures? What is the air temp across the condenser?  Does the truck have a sleeper unit also? Did you go over the system with a "sniffer" looking for leaks? Does the engine fan come on at some point with the A/C operating?

It is far more likely you have a leak than a "stuck"Tx valve.

As an experiment, I took one of my systems that was open when I bought the truck (condenser was missing) and had been for at least 10 years, I installed a condenser and rebuilt compressor but DID NOT change the Tx, and it worked just fine! If any Tx was going to stick, it is more likely that one would have. Years later I did change it out when the equalization tube nut rotted off the suction side elbow, the Tx itself still worked.