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A/C in a Burb

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wadinator, Jun 19, 2003.

  1. wadinator

    wadinator 1/2 ton status

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    My rear unit is blowing hot, but the front is still blowing cold. Any clues? It's an 87 Chevy Suburban. /forums/images/graemlins/burb.gif Thanks! /forums/images/graemlins/thumb.gif
     
  2. Rolled

    Rolled 1/2 ton status

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    I assume the rear has its own orifice tube. I would start there.
     
  3. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    I assume the rear has its own orifice tube. I would start there.

    [/ QUOTE ]

    That is the only thing I can think of, except maybe the tubes going to the back could be getting hot from bad insulation.
     
  4. wadinator

    wadinator 1/2 ton status

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    Oriface tube? What's that?

    Here's a link to a diagram of the rear AC unit in my burb. Can you pick out which object is the oriface tube?

    Diagram link
     
  5. wadinator

    wadinator 1/2 ton status

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    What is an oriface tube's purpose in life?

    PS: if the diagram isn't in the list of photos on the above link, it should be there before too long. I just uploaded it, and I think the web page has to verify the pic before making it available for viewing.
     
  6. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    What is an oriface tube's purpose in life?

    PS: if the diagram isn't in the list of photos on the above link, it should be there before too long. I just uploaded it, and I think the web page has to verify the pic before making it available for viewing.

    [/ QUOTE ]

    Well you see on the front where the number 22 is there is a 35 under it this is the seal to the connection where the orifice tube for the front is.
    I can't really see where the rear is.
    The orifice tube basically regulates the flow from the high pressure side to the low pressure side and creates the pressure drop which lets the gases expand and get cool.
    /forums/images/graemlins/thumb.gif

    Looked at it again and it looks like the one I mentionned is for the rear and below it is the one for the front.
    I don't know why they have them both close to the front though, I would put the rear one closer to the unit in the back.
     
  7. mosesburb

    mosesburb For Rent Premium Member GMOTM Winner

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    The rear A/C units typically have an expansion valve as opposed to an orifice tube. The valve is typically located in the rear A/C housing in the back of the vehicle. There is a screen in the valve that can get plugged (especially if a compressor has fragged in the past). Find the valve, it usually a has an inlet and outlet at a 90 degree angle to each other with a small capillary tube (similar to a mechanical oil pressure line) coming out of a "disc" on the outside of the valve, and in the inlet of the valve, you should find a screen, and hopefully, you will find it is plugged. Sometimes you can clean them out, but sometimes it is easier to replace the valve. If you need to replace it, the Delco p/n is 15-5481 or a Four Seasons p/n is 38683.
    Good luck.
     
  8. wadinator

    wadinator 1/2 ton status

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    But in order to replace the valve, the freon will escape, right? So I'll have to recharge the system.

    You know, now that I think about it, I had some work done on my AC this spring. The old 134 was replaced by 12 (or the other way around, the new cheaper stuff was put in). The air blew cold and worked very well after that. But then sometime in the last couple of weeks (while it was rainy and cool and I wasn't using my AC) the rear unit quit working.

    Could the freon change have something to do with the expansion valve plugging? And just for my info, why is it called an expansion valve?

    wade
     
  9. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    But in order to replace the valve, the freon will escape, right? So I'll have to recharge the system.

    You know, now that I think about it, I had some work done on my AC this spring. The old 134 was replaced by 12 (or the other way around, the new cheaper stuff was put in). The air blew cold and worked very well after that. But then sometime in the last couple of weeks (while it was rainy and cool and I wasn't using my AC) the rear unit quit working.

    Could the freon change have something to do with the expansion valve plugging? And just for my info, why is it called an expansion valve?

    wade

    [/ QUOTE ]

    When you changed, you changed from R12 to the new 134R.
    And yes if it wasn't done correctly it will plug it.
    Actually if you want to do it right, you should change the drier and the orifice tube as well as the expansion valve in the rear along with all the O rings.
    Reason is the new gas uses different kind of oil to lubricate and this one eats the old O rings and they will disintegrate and clog small holes in the system.
    I just did such a conversion on a 87 blazer. It was easy, and didn't cost a fortune.
    I did buy the cheap Harbor freight Gauges for $49 and the vacuum pump for $10 (it works off the air compressor), and the conversion kit was $30 bucks at Walmart and some O rings from Kragen for $20.
     

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