A/C Part Identification

[Bob Keating]

Greetings all!

I am trying to identify the part that is in the attached photo.

It sits atop the dash air conditioner condenser. It has a plastic cap on it similar to the ones used on the schrader valves. I am chasing a slow refrigerant leak, and when I removed the cap from this part, it was covered in oil. I am guessing this could be the culprit.

Any help would appreciated.

Bob Keating

2009 Cayman

[Ivylog]

Educated guess…an adjustable expansion valve.

[Bob Keating]

Thanks, but the expansion valve and compressor cutout switch are up front on the passenger side. Unless some A/C units have two?

This part looks almost like some kind of needle valve.

Bob Keating

09 Cayman

[Harvey Babb]

I have seen that type of construction on service valves. Some leakage around the stem is normal with them; the cap must be in place and tight in normal operation. I can't see the valve itself in the picture. Does it have a capped off connection on the side? 

 

[Bob Keating]

Thanks, Harvey.

I have attached a better photo with the cap on. It is mounted on a T connection on the upper end of the condenser coil. I can only assume that it is used to shut off the refrigerant in that line for servicing. if you look close, you can see the oily residue on the T fitting. Is it possible the cap o-ring is the issue?

Bob Keating

09 Cayman

[trailmug]

Yeah, looks like a shutoff valve like you'd use to pump down a residential unit.. never seen one on a mobile application. Any chance of enough hose slack to turn it 90 degrees and hook it straight up to the condenser? 

The O rings on those kids of fittings are the primary seal.. if it's replaceable, it definitely sounds like a promising place to start. 

Edited July 5, 2021 by trailmug

[Bob Keating]

Robert,

I think I will try to do just that.

Thank you for your input.

[Harvey Babb]

Yes, the O-ring in the cap is the likely problem here. The seal around the stem is a very simple one and only meant to prevent gross leakage while service is being performed. The "static" seal for long term is the cap. Older valves used a metal cap and worked just like hose fittings with metal to metal seal. The plastic cap with O-ring or gasket is the cheap way out. Hopefully the plastic cap isn't cracked...

While removing the valve would remove any possibility of a leak that would mean losing all the refrigerant, pumping down and refilling. You probably won't be able to pump the system down without using the valve so that doesn't sound like a real option.

 

Edited July 5, 2021 by Harvey Babb

[Bob Keating]

Thanks, Harvey, and thanks to all who replied to this post!

The cap seems to be intact, so I will replace the o-ring.

The compressor also has Schrader valves in addition to the ones up front. I will replace those, also.

Thanks again to all for the valuable input.

[Chuck B 2004 Windsor]

At what temp does the evaporator fan start running?  Most people turn on the dash air before the engine reaches normal operating temperature.  If one does, it causes the high side freon to get too high putting higher than normal pressure on the evaporator and associate parts that can cause leaks.    Chuck B 2004 Windsor

[trailmug]

That one looks like an electric pusher which is probably wired up to run anytime the clutch is engaged. Mine willl even do it engine off, key on.

[Moonwink]

The common name for this is "king valve" and it's purpose is to stop the flow of refrigerant allowing the system to be "pumped down" and stored in the receiver/condenser for service purposes.  Not very common these days.  I found this cutaway view of a similar valve that would bolt on to the compressor.  Yours don't look like it has a "packing nut" on it like the one in the picture.  Yes, the cap should seal it and yes, the oil is a sign of a leak.

This one has a "gauge port" which I don't think yours has.  Anyway, "backseat" the valve - meaning back the stem all the way out against the upper seat for use.  That should help seal any leak.  "Frontseating" the valve would stop the flow of refrigerant.

Edited July 5, 2021 by Moonwink

[Bob Keating]

Thanks, Moonwink.

I did  just that. So far, after replacing some o-rings and tightening some fittings, it seems to be holding pressure.

 

[Harvey Babb]

Moonwink I think you nailed the "why it's there" question. I hadn't seen that used in mobile systems at all and very rarely in fixed systems, so had been scratching my head about it's purpose.