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Isolation type A/C service valves

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  • Isolation type A/C service valves

    Hoping a picture will show these valves in use today for stationary A/C plus now antique automotive A/C at compressors. Allowed isolating compressor to hold the charge and be removed for assorted reasons or repairs,

    Here if it shows>
    A note is that 1/8th inch square operates it counter clockwise from memory is back to system operates again. There isn't a Shrader in these be warned,
    MetroWest, Boston

  • #2
    I've always known them as "backseat service valves" My 1992 Marmon Semi was the last vehicle I saw to come from the factory with them in automotive.
    The ones without the shrader need brass flare caps on the 1/4' service connections. The later ones used in my Marmon did have shrader core in the 1/4" flare.
    I think the main reason (other than cost cutting) they went away on automotive was you needed to know how they worked. You could destroy the compressor if run with the valves in the forward seat position.
    They are still in common use in commercial systems, and shraders aren't used (and sometimes larger flares than 1/4") to allow for faster flow when working on large capacity systems.
    I was sorry to see them fall from favor, in used them when space was available on my custom builds.
    With them complete service or even replacement of the compressor without the removal of the refrigerant is possible.
    On large stationary systems they are also often on the receiver tank, so you can close the outlet, run the compressor to fill the tank with the refrigerant in liquid form,, then isolate from the rest of the system so very little refrigerant is lost on a condenser, line or evaporator repair. Really fairly brilliant engineering.


    • #3
      Whilst fussing to make that show ran across new ones for sale like <$15 - big deal now - not.

      I think they are especially handy for one example rooftop units not the issue is inside sometimes multi floors down leave it alone just vacuum what you worked on.

      Also did some yachts compressor down in a bilge who know how lines were routed in some so isolate it. Had one (not mine) was a guest at a lot forever needing a boost up went by temps lines and outputs.

      OMG ice makers too! Laugh, it's whacked to see condensers are water tanks pulling "sea" water or what you are in to condense doesn't take much water vs air we deal with more of course.

      Laugh again, sea weed blocking inlet for water count me out I'm not scuba diving too!!
      MetroWest, Boston


      • #4
        They are just good engineering.
        One time, middle of summer, the two cyl recip compressor starts knocking. I shut the system down, swung into a truck parts place and bought a new compressor. Before I did anything, I closed the suction valve, and turn the compressor on for a few sec. The closed the high side valve, Changed the compressor, and hooked up the lines, leaving the discharge a little loose on the compressor, cracked the suction side to purge refrigerant through the compressor, and then tightened the discharge line, and opened the valves and went on my way with working A/C.
        No refrigerant, no gauges, no suctioning the system. May be not the ideal way to do it, but beats sweating all night in a 95 deg sleeper!
        Something you can't do without those little valves.


        • #5
          I can't speak for the big rigs at all no room to so much as park one here so ends that.

          I think that compressor is/was called an RV2, like some small engine. A bit noisy had one in a '69 Continental. It was already redone/new when I got the thing converted it no prob to 134a it leaked a bit so save the R-12 it was a resto job I did for myself just convert A/C stunk in that last model year of "suicide doors" was old when I got it.

          Panel vents low on dash made it hard to freeze (some old cars were freezers) what should have been top shelf A/C.

          Stuff today they'll cut a $1 buck item that was great if times mega thousands+ units sold I guess worth it to maker not customer doesn't notice till they own it - bummer.

          Notice how many vehicles now have NO high side port at all!

          I can't spend more on wild tools that would tell pressure thru scanner from HPCO no doubt,
          MetroWest, Boston


          • #6
            The RV-2 was Chry V twin that sounded like a lawn mower. They just had 1/4" flare ports on the head and at the STV valve/suction line.
            I thought, but could be wrong that Fomco used the York/tacumsha (recip twin) or the Harrison A-6 on their stuff. I don't remember any others in those years, but memory could be failing. The twin recip were the ones I remember having valves. They were often a "Flange head" in those day where the valve bolted to the head with two bolts and had a gasket. Then came Rotolock with the nylon seal ring (still in use in commercial units and my Marmon had rotolock head) then tube O ring.
            I liked the "suicide door Conti with the odd ball 462 V-8. They were smooth riding.
            Ford had an ad a few years later where a diamond merchant was spitting a diamond the back of a moving Ford. SNL later did a spoof where a Rabbi preformed a circumcision in a moving Ford. SNL has some funny spoof ads.


            • #7
              Crack me up. '69 for Continentals (last suicide doors) came with nuke powered 460 maybe still used for something out there?

              Movies - A 007 Bond movie put handcuffs on the two door handles (the enemy inside) people inside were stuck real good.

              Odd but that was a unit body so heavy was like 100% frame. 98 Octane required and passed anything but a gas station! Even at 3 tons of metal!

              I recall the SNL thing - quit most TV after the best of that early on.

              Truth is I found that car uncomfortable! Wrong options new might have helped?

              I started the resto it was a free car so room to waste some bucks on.

              Best A/C I happened to own was a 77 LTD Landau 400M 2V with looked like the A-6. IDK it never broke. Black car would blow cold before leaving a parking spot in full sun all day had to drive with gloves till steering wheel cooled off!

              Not too many great cars IMO from the 70's - lame engines, power about gone - if you cared.

              YOU know your compressor names better than I ever will I just wanted smart placement of all the junk out of the way for other anything - that's over today totally.

              Onward have to go,
              MetroWest, Boston


              • #8
                I'm not real up on the '60's Conti's but in the late 80's there was a nice one that used the shop I was working for. I only drove on short test rides, but it seamed to ride well on the city streets.
                That 462 pre-dated the 429/460 block. The head bolted on the block at an angle that was not a 90 deg parting surface, so the angle became the wedge shaped combustion chamber. IIRC GM did the same thing on one of their V-8's as well. The 462 fuel pump was high up in the V of the engine at the front.
                I worked at another place that had a whole fleet of 460 Fords in 1 ton vans. They would have been better off with 300 in lines for what they were using them for (short distance airport shuttles).


                • #9
                  Somehow I don't know about the 462. 429 I knew of as a CobraJet TMK all sure knew how to hog fuel as well as GM, and the Mopar's 440.
                  Owned several Caddy 472s pre smog, high compression all of them were nuke powered things and needed to be for the tons of car they were used in. Most were also marine except the 472 just the Caddies - they didn't share with other stuff, truck/vans nor made "counter rotating a must for marine dual engine use the "Big" three gave up to easier plain Chevy designs better in many ways long term. IDK, I think easier to make special use parts for and fast engine changes for marine (used to love the yachting stuff unreal to be down in bilges with fuel burning like some volcano backwards OMG what a roar carbs can make!

                  The real marvel is how to exchange heat - no radiators rather heat exchangers and wet exhaust for waste water a must can't have glowing metal in with fuel of any kind quickly becomes safer to use diesel get the HP back via turbo charging.

                  Those also lasted longer big time you'd know with the trucking rigs more hours for endless use plus by rights is simpler fuel to make and store indefinitely not as perishable as the gasolines which are not anymore a huge mistake to use ethanol to dilute it. Hmmmm - that could be better used land for silly things like FOOD!

                  All this fun over the subject of a smart isolation valve must too useful so let's dump that idea and complicate things to useless and impossible and shorter life the makers just want production fast and furious to make new not durable anything.

                  My latest dismay is how "plastics" are NOT so durable nor tolerant for the extremes like this site about A/C - it doesn't belong involved IMO but wasn't asked either :-)

                  MetroWest, Boston


                  • #10
                    The 462 pre dated the 460 and I think was a Lincoln only engine, earlier engines were "MEL" (mercury, Edsel, Lincoln). I think Ford discontinued it in 65-or there about. It was a smooth big engine, but as I remember didn't share any parts with any other. I think the Bell on the C-6 trans was even unique to that engine, so to rebuild you had to have a C-6 case for the 462.
                    IIRC that was only for the latest 462's early ones used the cast-iron "merc-o-matic" trans with the separate bell, like the C-4 had.


                    • #11
                      Here is a York (aluminum case, tecumsha would be iron case) with the service valves. Next is the Harrison A-6. Gm learned a lesson. When the :"Detroit Diesel 1st came out it was badged and called the GM diesel and was not sold to any other truck maker save some low production makers. They learned they could make a whole lot more money by calling it Detroit and selling it to the competition. Hense the "GM A-6" got labeled Click image for larger version

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                      The York would have been on most Fords from the 60's and early 70's while the A-6 was used in the later years until GM stopped making them
                      I used the York on my Aux heating/cooling unit on my Truck as that style could be turned either direction. The A-6 has a lube pump and can't be turned either direction.