Bypassing sleeper AC 1992 KW t800 ?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by 57ringo, Sep 30, 2022.

  1. 57ringo

    57ringo Bobtail Member

    26
    1
    Dec 21, 2008
    Emporia, ks
    0
    I'm bypassing the AC in the sleeper in my 1992 T800, I am installing a new grilledenser, york compressor, drier and expansion valve. My question is how much r134a freon should I put in since deleting the sleeper part of the AC? It will be basically a day cab version now and how much oil should I put in the new compressor before I install it. It came shipped with 12oz that I emptied out but the APAIR guy said to put 2oz/lb of freon total but start with 2 oz in the side of the york compressor and then distribute the rest throughout the system but he said the daycab freon amount should only be about 2.5 lb total in it so that would only be 5oz of oil total. MHC Kenworth service said to put in 3.7 lb of freon so I'm not sure what I need to do.
     
    Last edited: Sep 30, 2022
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  3. Rideandrepair

    Rideandrepair Road Train Member

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    Aug 8, 2015
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    2.5 sounds low. But 3.7 is what my Freightliner holds w/sleeper. Most Pete’s and KWs hold more than mine, closer to 5lbs. Maybe 3 lbs? I don’t know. Can only guess. Bunk evap and both lines are probably 2-2.5 lbs. Seems like half of original should be enough. Basically half as much system. I think I’d try 2.7-2.8, assuming the origin charge was 5.0 lbs. Total oil should be approx. 7% of Freon by weight. Counting 1 oz. left in compressor after emptying. So 2.7 x 16oz.=43 oz. Do about 3.5 12oz. Cans. 2.7 x.07= 3oz. So add at least 2 oz. oil, no more than 3 for sure, assuming there was 1 oz. left in compressor. It’s better to be a bit low on oil than too much. Oil displaces Freon, and makes the compressor run hotter than normal. Proper Freon is needed for compressor cooling, to avoid shortening the life. Ideally, a tag on the firewall of a KW Daycab would tell for sure. Maybe initially 2.5lbs. and 2.0 oz. oil. See what you get. If it doesn’t cycle off while idling, clutch running full time, add some more Freon, till the high pressure switch cycles off, and fan kicks on. Then stop. Watch it cycle, clutch should be engaged at least as long as it is not, up to 2 times as long engaged than it is not engaged. Hotter and higher the humidity is, the more it will cycle off. If it stays off longer than on, or starts short cycling, on and off a lot, it’s overcharged. Best to pull a vacuum and use gauges. But if you’re in a bind, putting on a new dryer, along with the oil. It’ll work just fine. Small risk of moisture causing problems, freezing and causing rust in the system. Realistically though, I’ve never had a problem on mine. Did it that way for years.
     
    Last edited: Sep 30, 2022
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