Replacing the o rings on leaking HVAC service valves

A demonstration of how to replace service valve o rings on split system air conditioners and heat pumps.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

[robertfleming]

I have replaced several of these caps where someone has tighten so tight the top of the cap broke off or split the top! I also have had very little success changing the O ring. I think the valve itself wears and causes the leak not always the O ring. I've had better results changing the entire valve. Great video!

[HVACinstructer]

For thread leaks I have had good success with Nylog sealant by Refrigeration Technologies, Anaheim Calif., red bottle for R-22 (CFC-HCFC), blue bottle for R-410a (HFC), seems to work a little better than Leak Lock. Hope this helps all and thanks for the video. I've learned a lot from you.

[grayfurnaceman]

As leaks are the worst problem we have in this industry, I think the best approach is to cover all basses with effective repairs. A schrader cap is not a repair for a leaking schrader. As you know some manufacturers use a plastic cap so not all manufacturers agree. Also, unlike the schrader, the cap is not being pushed closed by system pressure. Thanks for a great conversation.
GFM

[ltback]

Thank you very much for taking the time to make these videos, you are helping far more people than you can imagine. I completely agree with your comments and it is obvious that you have been doing this for a long time and are talking from experience. I am shocked by some of the other comments thinking that the caps are for sealing.

[grayfurnaceman]

Yes. The oxyacetylene torch is the best choice. The turbo torch simply cannot come up with the temps to make a quick heat up of a refrigeration joint, especially with a valve nearby to absorb the heat. I have seen many valves damaged by the air acetylene torch and they are not suitable for this type of work. Some will disagree but that is my opinion.
GFM

[cladnar]

I discovered oil coming out the service valve on my AC 6 or so years ago. I had a friend charge it up every summer. I tried to seal the cap like you mentioned not to and with automotive gasket material it lasted three years but is leaking again and worse. I tried to remove that valve core before and it seemed to tighten up as it came out and I aborted the project. After viewing your video, I tried it again and it came out. The o-ring was worn and cracked. I purchased a bag of green AC O-rings from a hardware store and a couple more at an Auto parts place that had a closer size fit. I put in the one from the auto parts place. My AC friend, who by the way said this would not work, came over and pulled a vacuum on my system and it held tight. There was no need to recover refrigerant since it had all escaped long before. He then charged the system and it has worked perfectly for over a month now. Next summer it will get another test. You video helped me save a lot of money since 3 different techs told me to replace the unit, and this method worked for me. Thanks for the video.

[grayfurnaceman]

As for the threads of the valve cap, I guess I also have to disagree. The threads of these caps are not tapered so they only tighten on one side of the thread. Sealers sometimes work but I would not hold too much hope, as I have replaced many valves with sealer on them. Sometimes there is more than one to do something and both ways work. None of us know it all as our experience is limited. Again, thanks for the conversation
GFM

[Brnlandry]

Something about the psi converted in sq inches was like 10000psi that was 15yrs ago I just don’t use it except to purge while soldering love the channel by the way.

[grayfurnaceman]

Yes I have been dealing with these things since 1977 and they have not gotten any better.
GFM

[michaelmonaghan]

Sir, i, went to O'Reilly auto parts, and found an assortment pack of green automotive a/c o-rings. and was able to match the old carrier o-rings. so far it has worked perfectly. Thanks for the help.

[HVACinstructer]

Continuing again, Personally, I have never had to replace the o-ring, even if overheated, because the cap performs the final seal, it tightened correctly. I HAVE had to replace the whole valve only if some jarhead severely over tightens and deforms the valve, as you mentioned in another video.

[techfive]

I do property maintenance with 170 units on the roof. I keep the O ring wrench and the rings in my bag. Even with plumbing o ring kits, it's a task to get the right one( harbor freight has a kit that matches.. I have to give it a hard slap to get it to seat with the threads. It beats carrying the torches on the roof. It is also a $.015 repair vs $20 valve replacement. With mo99 retro in place, I need every bit of the recurring budget money that I can save. I fixed a leaking king valve today and converted to mo99, the cond was 21 yrs old. The people moved in a complimented on how great the ac was working.

[heavydiesel]

Amazing they seal at all with just the one o ring in them.
If they are leaking and you get a lot of liquid condensed between valve and cap, if the temp goes up it will pop just like an overfilled ref cylinder with not enough expansion room.

[psyche]

Thank you for your reply back to my question in prompt, we find all over the internet we couldn't find o ring.. our suction valve size is 7/8" what size o ring we have to purchase? Any special shop? or any kind of o ring.. We look up the O ring Store site..they have so many o ring but we can not determine which size we have to order.
the size chart  is actual size is ring size? What is nominal size? Thank you so much for your help!

[UtwoBed]

Have you noticed all the new service valves come with a factory crimped top with no way to remove the piston to get to the O-ring? Bummer.

[grayfurnaceman]

As the brass cap is quite thin, I don't agree it is capable of an effective seal. Some of these caps have bulged up like a ballon in 410A systems. The first of these I saw were the Carrier RQ systems that used a gasketed cap that would also leak like a sieve.
GFM

[torresdelpaine]

I have a suction side service valve that is leaking at the o-ring. There is still a pre-charge of refrigerant held in the outdoor unit which hasn't been released into the line set yet. The service valve doesn't have the snap-ring option and has formed edges, which means the service valve needs to be replaced. If I need to evacuate the pre-charge into a storage container for the service valve replacement, what are your thoughts on just removing the service valve all-together and just straight brazing the line-set into the outdoor unit. Obviously, I can replace the refrigerant using the outdoor unit's schraeder valve connectors at the reversing valve (air source heat pump).

[gfriedman]

The problem is the newer service valves do not come with retaining rings any more - not sure why. The tops of the outside body are crimped to retain the valve plunger which renders them unserviceable. You either go with a band-aid fix like a gasket underneath the cap or replace the entire assembly. Really - this is such a major problem that I am baffled a better solution has not surfaced. If the EPA was serious about refrigerant getting into the atmosphere they would have created a task force to remedy this problem.

[grayfurnaceman]

The most common valve leakage problems I have seen are caused by overheat of the valve when brazing. There is no repair for this, only replacement of the valve. I think we will always disagree on how to deal with this most common failure but I guess the final answer is whatever works for you.
GFM

[phillipnowicki]

Do you remove those valves when brazing or is using a wet rag over the valve good enough?