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    Misbehaving clutch cycling switch

    My 73 Blazer has had a non functioniing clutch cycling switch.. It is new, as is everything else in the system.
    The new switch has never cycled off, even at really low vent temps of 32.5. After much discussion and thinking about it, I decided to leave it as is for awhile. Being in Phoenix AZ, it isn't a huge problem.
    This morning I was on the highway about 4AM, Ambient temp was about 88. The vent temp got to 37.8, and my clutch cycling status light stated flickering really fast. ( I installed this and a clutch shutoff switch some years back when I used to tow with it)
    It is a great way to see just what is going on with the clutch..
    I surmised that the switch is trying to work now. I think that as an R12 switch, it may have set on the shelf for so long that it became stuck, and is now working it's way loose.

    My concern is that it may over heat the clutch with the rapid on off it is doing, causing it to slip. I turned it off a couple of times with the manual switch, and it went right back to the flickering light.
    I am considering just jumping the switch terminals for a few days to see if the switch will settle down and start working normally. Since it's been running awhile with it non functioning, there would be no real harm right now. I also considered just replacing it, but it's replacement may well be in the same condition.

    I estimate that the evaporator temp was right around 32 this morning when this occurred...

    Thoughts?

    #2
    So... is this an orifice tube system? I would have thought it was a VIR or Tx system with a frost switch, Somewhere I have a '73 Chevy truck manual but can't lay my hands on it right now. Anyway you cut it, there is supposed to be a difference in cut-out cut-in temps/pressures to prevent short cycling. IS this a temp operated switch? I would think so given the year we are talking. Calling it a "clutch cycling switch" is confusing me, makes me think it is a pressure operated switch like in a CCOT system.

    Comment


      #3
      Ever think of installing a dash-mounted toggle switch to turn the compressor off and on? If your evaporator temperature is really low like 32F, then on days when we do have some humidity, you could get ice freeze up on your evaporator.

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        #4
        I think he has that and a pilot light, he said he added that when he towed a lot with the Blazer

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          #5
          Heard of the rather toasty temps in your area! Hey - great to have the cool and probably get away with it as air pretty dry there - Phoenix. Verify that vent temp with another thermometer. You said 37.8 later at 88F ambient would be plain excellent but really shouldn't stay even there.

          Do you have the old switch? Check - it's old enough I can't remember but should screw on with just a rubber O ring. The old one would show that inside it could to just that so you don't lose your charge the reason being it's probably adjustable! I could be wrong but think tightening will raise cut out pressure. Just go 1/4 turn no more at a time if you try that.

          Watch out! IF there's not Schrader it will blow out all refrigerant you don't want nor get hurt. It would hiss even if you remove them fast just a very short time then quit you know you are good to check while charged.

          Check real temp of air coming in thru grille not just that forecast temp. Road surface could be a LOT hotter so this is exceptionally cold output if higher air temp than you thought.

          BTW - A couple times put the Ford from the 80s common larger mushroom cut out switch with plug if used so be it either spliced in or lease OE and make up good wire just spade terminals definitely adjust. There a risk in doing that it could leak so check.

          Cycling clutch? Check the air gap and set to close if not. About .020 is a standard or folks would say a folded standard business card paper would be snug.

          Trivia: If clutches friction surface is hot from cycling it's losing magnetic force to pull it in or keep it engage may cool and be more magnetic! Funky but the hotter the metal the less magnetic! A maybe to rule out and might need checking function of the clutch of its coil,

          Tom
          MetroWest, Boston

          Comment


            #6
            Originally posted by Cornbinder89 View Post
            So... is this an orifice tube system? I would have thought it was a VIR or Tx system with a frost switch, Somewhere I have a '73 Chevy truck manual but can't lay my hands on it right now. Anyway you cut it, there is supposed to be a difference in cut-out cut-in temps/pressures to prevent short cycling. IS this a temp operated switch? I would think so given the year we are talking. Calling it a "clutch cycling switch" is confusing me, makes me think it is a pressure operated switch like in a CCOT system.
            You are correct. It originally had a temperture probe into the evaporator. Those did not seem to be all that reliable, and now seem to be unavailable. So I installed the clutch cycling switch instead into the accumulator. Like I said, it was new along with everything else about 6 weeks ago. But it never worked.

            In am figuring that it is trying to start working now. Probably been sitting on the shelf for years and got stuck. (R12 switch)Since under my present conditions, it really isn't critical, I came up with the jumping it idea. Perhaps with some more of it trying, it may free itself up. And I can always manually shut the compressor off with my switch, if I encounter super low vent temps.

            One thing for sure, i do not like the rapid on/off that it is showing me now at low temps. That can't be good for the clutch.

            But if I leave it screwed in to the accumulator with no wires attached to it, that may just allow it to heal itself. Of course I want it to be working properly when it will be needed more than it is presently.

            It would be warrantable, but I figure the replacement may be in the same condition.

            Comment


              #7
              Originally posted by Cornbinder89 View Post
              I think he has that and a pilot light, he said he added that when he towed a lot with the Blazer
              You are correct. So I can control the clutch manually.

              Comment


                #8
                Originally posted by huntindog View Post

                You are correct. It originally had a temperture probe into the evaporator. Those did not seem to be all that reliable, and now seem to be unavailable. So I installed the clutch cycling switch instead into the accumulator. Like I said, it was new along with everything else about 6 weeks ago. But it never worked.

                In am figuring that it is trying to start working now. Probably been sitting on the shelf for years and got stuck. (R12 switch)Since under my present conditions, it really isn't critical, I came up with the jumping it idea. Perhaps with some more of it trying, it may free itself up. And I can always manually shut the compressor off with my switch, if I encounter super low vent temps.

                One thing for sure, i do not like the rapid on/off that it is showing me now at low temps. That can't be good for the clutch.

                But if I leave it screwed in to the accumulator with no wires attached to it, that may just allow it to heal itself. Of course I want it to be working properly when it will be needed more than it is presently.

                It would be warrantable, but I figure the replacement may be in the same condition.
                ! I missed that comment somewhere! Seriously I didn't think any were non CCOT only set ups. Accumulator mounted switch with the low port on the same unit.

                If somehow this is not close to OE intentions not sure what to say now. It could drop low pressure but don't understand how if the two ideas were fighting with each other would behave as I wouldn't do that unless somehow no choice.

                Long time ago and didn't think "Chevy" ever used a "thermistor" is I think was it's called sensing temp not pressure - Cadillacs did I think some Buicks used a fuse but blown was blown you got another if not power to clutch??

                Not sure but temps you get are good. The rapid cycling can't be good for it if too often.

                I have to plead "IDK" what you can get for this for funky parts if so and easily?


                Tom
                MetroWest, Boston

                Comment


                  #9
                  From what I can remember from back then, they had a VIR (valves in receiver) which has a large accumulator looking thing, It took a replaceable desiccant "bag" with the valves in the removable top portion. A cycling pressure switch I don't think would work with that system. There are a million temp switches with a probe that can be placed in the fins. There are both fixed and adjustable types. Click image for larger version

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                    #10
                    As far as thermostatic switches Heavyer GM's use a MEI 1331 which is a 24" capillary tube switch fixed 34-38 deg or about a 5 deg off to on temp.

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                      #11
                      Click image for larger version

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                        #12
                        Originally posted by Cornbinder89 View Post
                        From what I can remember from back then, they had a VIR (valves in receiver) which has a large accumulator looking thing, It took a replaceable desiccant "bag" with the valves in the removable top portion. A cycling pressure switch I don't think would work with that system. There are a million temp switches with a probe that can be placed in the fins. There are both fixed and adjustable types. Click image for larger version

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                        That I do not have.

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                          #13
                          Originally posted by Cornbinder89 View Post
                          Click image for larger version

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                          That looks similar to how it was.

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                            #14
                            Click image for larger version

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ID:	261 Does it have a pilot operated Absolute valve?

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                              #15
                              No. It is a standard CCOT affair.

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                                #16
                                Well, I must admit I am confused, the CCOT didn't come in until 1977 according to what I have read, so 1973 should be a Tx
                                I know that there are some "conversions kits' made to covert the old style to CCOT, could that be a possibility?

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                                  #17
                                  I've gotta plead out of being for sure. Knew these vehicles new, many the Suburban single A/C or none. ZERO trucks known of with A/C for the body/chassis change of 1973 from the 1972 a total makeover. I'm pretty sure of the 1974 total CCOT set up bought new by family.

                                  For whatever reason other than saving a fortune new for A/C most wouldn't pay where I am - still in same area within 10 miles all that time. Not needed and a pest in the way of other routine work.

                                  Luxo vehicles where A/C was standard with the car opted out for a credit option on the window sticker.

                                  Huh - try my luck at picture posting?

                                  Here if they show.....

                                  >>
                                  >>
                                  Accumulator shown and orifice tube and holder was in evaporator. That info could be wrong but was the only items show when these were sold new looking up for 1974 same as 1973 as far as I know bolt for bolt,
                                  Tom
                                  MetroWest, Boston

                                  Comment


                                    #18
                                    Just looked up the Pick-up truck version and was correct or both are wrong? Same parts, in stock still for next day delivery! Both or all Blazer was just a shorter Suburban the pick-ups all considered TRUCKS exempt from many safety features that the "Passenger Car" required shouldn't matter can't prove it changed A/C designs.

                                    A reason for a difference totally could be missing? These vehicles had to comply for Calif. emissions or specs for "High Altitude." There was a wide selection of engines and transmission choices that just may change the whole scene. Dashboards looked identical to your view - what was behind it of course would matter if it came with A/C or not,

                                    Tom
                                    MetroWest, Boston

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                                      #19
                                      What I'm reading could be wrong. I just remember a lot of VIR back then and then the changeover to CCOT in the later 70's but my memory could be off and what I've seen is not OEM manuals, Can't locate my '73 Chevy truck manual, which I know would be accurate. I always thought the CCOT was a later design, but am willing to admit I don't have hard evidence for that. Our '73 Chevy Pick-up didn't have A/C, so I can say for sure.

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                                        #20
                                        I hear you. I wouldn't remember and was that much younger (that's a long time ago) to remember the vehicles in person most no A/C some no radio either. I wouldn't have been working on anything A/C nor waste any money on tools for it till later but did by about 1978 I think?

                                        I was just looking up parts for OE replacements - choose your place if a brick and mortar they'll show pictures and have some pro-edition AllData if you just get on their mailing list. I've found a lot totally wrong and have had or worked on stuff that old and older people knew from new still.

                                        This particular body if you look inside an original door was just misted with a grey primer not rust resident at all. This is "rust belt" central because of rock salt use excessive here plus common for a quick warm up or sun during day mid-winter with snow melt back becomes ice again daily re-salt over and over is a nightmare on vehicles.

                                        These - stated a 1974 Suburban new had body rust holes you could park a tennis ball thru by 3-4 years old! Yikes. Mechanically excellent till the seat tilts from floorboard rust or some frames drop to the ground - insanity.

                                        In short it means if you had sprung the extra for A/C the flipping vehicle was junked from rust before A/C anything needed a thing and then wouldn't fix it anyway unless just some stupid dirt cheap something.

                                        So can't argue with what's archived on the web just this one saw just the one I knew and drove and went a zillion miles but failed to rust,
                                        Tom
                                        MetroWest, Boston

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