Odd A/C Behavior

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Roteck, Oct 12, 2019.

  1. Roteck

    Roteck Light Load Member

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    I have a 2015 KW T680 and my A/C doesn't blow cold air when it's above 75 degrees outside. I'll set the control to 60 degrees and it blows 70 degrees on the dot. I'll set it to 62, still blows 70. The air also feels humid. It blows 70 until I set it to 72 and hit Auto. Then it blows 64 degrees and the air is nice and dry. I'm told it us supposed to be much much much lower than that. It's been going on so long that I have forgotten how cold it can really blow. Every setting higher than 72 seems to work fine. Another thing it's doing is the blower motor will kick on and off for a while after first starting it but after about 5 to 10 minutes it stays on. Also, recirculate mode does absolutely nothing at all. I've replaced the control unit on the dash and that didn't fix anything. The compressor readings would have a spazzy needle when it got into high range just before it kicked in. The truck has 600k miles on it so I decided to go ahead and replace the compressor, dryer, and expansion valve. Still no change, same exact behavior. Anyone know if this is a compilation of failures or is all related to something specific?
     
  2. Goodysnap

    Goodysnap Road Train Member

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    Get into the shop and have ESA hooked up. This HVAC system Is computer controlled.

    You likely have a intermittently shorted temp door actuator or possibly a broken door as they are plastic and have been known to break. The blower random shutoff is common when faults come active in the system.
     
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  3. spsauerland

    spsauerland Road Train Member

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    A lot of HVAC been addressed with software updates. Screenshot_20191013-085821.png
     
  4. Roteck

    Roteck Light Load Member

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    Alright. What is ESA?
     
  5. Goodysnap

    Goodysnap Road Train Member

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    Electronic Service Analyst.

    It is the the Paccar communication tool for Cab and HVAC controls.
     
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  6. Roteck

    Roteck Light Load Member

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    I have a custom tune on the ECM due to it being deleted. Would that be an issue when trying to update the HVAC controller?
     
  7. Roteck

    Roteck Light Load Member

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    OK thanks. I'll see if I can get it hooked up next time I get home.
     
  8. spsauerland

    spsauerland Road Train Member

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    No, but stress that is only work that you want performed. They are supposed to report you and refuse work if Emissions tampering is suspected.
     
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  9. Goodysnap

    Goodysnap Road Train Member

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    Make sure there are no open campaigns that would require engine software changes. Dont ask, dont tell. As long as they are not working on engine or emissions it's all good.
     
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  10. Roteck

    Roteck Light Load Member

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    I have a shop I go to for everything that needs doing on the truck. The same shop that did the tune so I just want to make sure that the HVAC would be separate from the actual tune.
     
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