I recently converted from R12 to R134 and replaced my 1982 CE AC system with the following parts from Zip-Corvette (AH-XXX):
77L-82 AC Accumulator/Drier (AH-331)
80-82 AC Evaporator Core (AH-352)
78-82 AC Compressor Muffler & Hose Assembly (AH-306
77-82 R4 AC Compressor (AH-312)
80-84 AC Compressor Low Pressure Cut-Off Switch (AH-375)

The 77L-82 AC Accumulator/Drier (AH-331) comes with a schrader valve attached. This valve will accept 80-84 AC Compressor Low Pressure Cut-Off Switch (AH-375). The problem is you cannot screw the switch to the Schrader valve because the radiator overfill reservoir is touching the AC Accumulator schrader valve, when installed. You cannot rotate the AC Accumulator to resolve the conflict. I recently discovered the actual OEM 82 CE accumulator does not come with any schrader valve attached at all and the AC Compressor Low Pressure Cut-Off switch must be attached at the Evaporator Core tube or muffler/hose assembly.

On the 80-82 AC Evaporator Core (AH-352), one of the connecting tubes has two schrader valves attached. However, the 80-84 AC Compressor Low Pressure Cut-Off Switch (AH-375) cannot be used because of two reasons, (1) the threads on the switch will not screw to the Schrader valve threads on the AC Evaporator Core, (2) the location of the O-ring on the AC Compressor Low Pressure Cut-Off switch is after the the threads will not seal. The O-ring location must be placed after the threads and not before the threads inside the AC Compressor Low Pressure Cut-Off Switch. I am looking for a low pressure cut-off switch that has the O-ring after the threads. Bottom line, the 80-84 AC Compressor Low Pressure Cut-Off Switch (AH-375) will not work with the 80-82 AC Evaporator Core (AH-352). Question? Is there another replacement/reproduction AC Compressor Low Pressure Cut-Off Switch?

End view of new low pressure cut off switch. O-ring location down inside past threads.

Side view of low pressure cut off switch.

End view of old low pressure cut off switch. O-ring location before threads start in side switch.

Side view of old low pressure cut off switch

 

That switch should thread and is supposed to go on the lower of the evap fittings. Those switches are pretty standard in thread depth.

 

Mrvettenick,
The threads on the low pressure switch are cut different than the threads on the evap. Another issue is the location of the o-ring. If you look at the end of the low pressure switch the o-ring is positioned before the threads. However, on the evap schrader valve the o-ring has to be positioned after the threads in order to properly seal on the evap. There isn't a ridge on the evap schrader valve to provide a seat for the o-ring to sit and it won't seal and will leak. We can talk. Send me a text at mcumm012375@gmail.com. Thx

 

Try this. It is specifically for R134 and has no oring. I keep a couple for spares. I also checked the Corvette catalog, and they don't call for an oring.
https://www.4s.com/en/ecatalog?year=1982
Part Number 36674
BTW I've never seen a switch with a metal fitting. The nylon seals better, and is more forgiving.

 

Mrvettenick,

Ordered suggested part as stated. I also ordered the associated harness connector. I do remember reading in a Corvette Magazine.com article on 77-82 Corvette Air Conditioning Conversion, posted on April 5, 2016. It stated the shrader valve stems are not compatible with the new R134A systems and require removal. I'm assuming this is why O-rings are not needed for the pressure switch as you indicated in your previous reply.

Thanks
Mcumm

 

Not sure if I agree with that article. Be aware that if you remove the valve, if the switch needs to be replaced, you'll empty your system, I would call 4 Seasons tech line and see what they say, Maybe they were referring to the seal on the schrader valve, and that it should be replaced with a valve that had a compatible seal. But all new components are compatible in recent years.

 

Mrvettenick,
Agreed. After reading your response it dawned on me the schrader valve can't be removed. That said I reached out to Four Seasons to confirm their switch, pressure system mount, part number 36674 is screwed on my new evaporator schrader valve without any O-ring involved and a seal will be obtained when the switch is screwed on tightly. Stay tuned for more input as it unfolds.

 

Glad to help, and good luck. It's getting warmer, and we need that AC.

 

Mrvettenick,
Received the low pressure switch and it came with a green O-ring. As you had stated earlier in this thread, the O-ring is not needed........correct? Just want to be sure after the switch is installed that it will not leak out my freon.

 

If it's the 4 seasons with the plastic female, then no. Is the o ring inside, or just packed separate?

 

Mrvettenick,
See attached pic of switch with green O-ring in place. The tech from Four Seasons stated and I quote: "Switch part # 36674 normally use an O-ring that mounts on the base of the switch port in a machined groove. Since your replacement evaporator does not have this groove, a small O-ring that fits up inside the switch fitting can be used. The part # for this O-ring is 24605. A switch sealing without an O-ring is for old school R12 systems where the switch and port both have tapered (flared) seats and the switch has a metal fitting, not plastic. Unfortunately, R134a can leak past this type of sealing where R12 did not."
My initial pic I posted showed this type of switch. Anyway. I ordered the suggested green O-ring which is suppose to work.

Four Seasons low pressure cut off switch part # 36674

 

Did you ever think of just buying the Shrader Valve adapter kit for CFC-134A?....they are available at AutoZone and etc....made by Interdynamics.

 

L-46man,
No I did not. Unaware such a part existed. After talking to four different corvette parts suppliers I cannot believe I am the only one who has this problem with the current pressure switches being incompatible with the current replacement evaporator schrader valves. One would think the evap schrader valves would have been manufactured to at least the OEM specs. Everyday owning a vette especially since I am not a gear head but do know my way around a car, is exciting while always challenging. Thanks for the info though. I will check this out.

 

I've never saw a metal switch. That's why I said to give them a call. So, it worked out because the metal one would not have worked.

 

Mrvettenick,
Back again. Still have not resolved my low pressure switch issue. After speaking with manufacturer who suggested to place a smaller O-ring down inside the switch. This did not work. Two things. The switch still leaked after screwing it onto the AC evaporator and the O-ring restricted the small orifice located down inside the bottom of the switch. I have attached a pic which indicates my problem. This pic of my old evaporator (OEM). My new evaporator does not have this seat for the O-ring to rest on and thus create a seal. I'm currently searching for an OEM evaporator and not a reproduction or replacement. Neither of these have this seat for the O-ring.

 

Do you have a photo of the new evap fitting?
BTW, what brand of evap did you get?