A/C Problems: Please Any Help Would Be Greatly Appreciated

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Gear&Clutch, Jun 18, 2021.

  1. Gear&Clutch

    Gear&Clutch Bobtail Member

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    My husband drives a 2014 Kenworth T660, it’s got a Bergstrom hvac in the sleeper. A couple weeks ago we were going down the highway and the freon lines blew by the compressor by the engine. So for a few days we had to go without ac, we didn’t even bother turning the fans on because it wouldn’t do any good. We had our mechanic replace and charge the lines, and now the cab ac blows ice cold air but we noticed that the sleeper bunk only blows room temperature and doesn’t get cold. My husband has traced the lines, checked the fuses and everything seems good. So he called the mechanic and his only idea was that the hvac might be clogged. The only thing that makes us question that is that it was blowing cold air the same day the lines blew. So if we haven’t ran the fans or done anything after that point, we don’t know how it could’ve gotten clogged because we had it shut off until the lines got fixed. Hubby has resigned himself to having to pull the bed up and manually check the hvac vents to make sure that they are indeed clogged. But if they’re not. Is there anything else we can check before we decide we have to take it back to our mechanic to have it looked at? Is there anything we might have overlooked, or should check? A few side notes, the heat works just fine, and it goes back to room temperature as soon as you switch it back to ac. The blower works fine, plenty of air. Our truck has a small studio, so the bottom bunk is a bench. That’s why we were hoping someone might have any other suggestions before he has to go and tear the bed apart.
     
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  3. reeferwrencher

    reeferwrencher Medium Load Member

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    Never worked on them but isn't the compressor for the sleeper a hermatic that runs off battery power when you re stopped at night?
     
  4. Gear&Clutch

    Gear&Clutch Bobtail Member

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    Honestly we’re not sure, we usually idle through the night anyways because i use a cpap machine.
     
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  5. reeferwrencher

    reeferwrencher Medium Load Member

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    Yeah I'm not sure but the 2 ac systems are likely independent of each other.I would look into that before you go any further with it.Some of the highway guys here should have knowledge of that unit.Good luck with it cause it's getting hot now.
     
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  6. Goodysnap

    Goodysnap Road Train Member

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    Replace the bunk thermal expansion valve. It likely got debris or contamination from when the lines were off. This is the most likely cause.
     
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  7. Rideandrepair

    Rideandrepair Road Train Member

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    The only other thing I can think of checking is the heater control valve under the bunk. If it’s bad and not closing, letting hot coolant circulate, it could be cancelling out the a/c cooling effects. In other words the heats sill on. Turning off the 2 water valves under the hood going to the bunk, will guarantee it’s off. And if the A/C blows cold, you know the valve under bunk for heater core is bad. That’s assuming the KW works that way. I’m not sure. It may rely on blend doors for hot and cold. Either way, it has hot coolant going to the heater core. Shutting it off at the engine might be worth trying. To rule out a bad bunk valve.
     
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  8. Rideandrepair

    Rideandrepair Road Train Member

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    Another thing to look for is condensation dripping from the bunk just like the cab does, shows it’s working, even if only somewhat. In high humidity especially, should be able to see condensation dripping from the lines going in under the bunk as well. If both lines are hot/warm with no condensation, chances are the expansion valve is stuck. Also if it’s iced over, it’s stuck. Sometimes it can become unstuck by turning it off and waiting a couple minutes and turning it back on. This almost always works when it’s iced over, allowing it to thaw out, then it works for a little while till it gets iced over again.Sometimes you can hear it gurgling. A little bit can be normal, but a lot of noise from the expansion valve isn’t good. Icing over could be from moisture in the system, causing tiny ice particles to block the operation of expansion valve, or an improper amount of Freon, or a bad dryer. Wouldn’t hurt to check the bunk HVAC filter if equipped, and if possible take the blower out, clean the evaporator Finns. A Truck that old, if it’s never been done, is probably covered with dusty moldy Lint. You can wipe it off with a sponge or rag, spray it with Lysol or equivalent, blow it out with an air gun. Need to ask mechanic if he changed the dryer, and pulled a vacuum. I’m not suggesting he did a bad job, probably just trying to save you money. I only replaced both of mine once in 20 yrs on my Truck. Goodysnaps probably right, he works on this stuff everyday. He knows what’s most commonly seen. Expansion valves probably original. A lot of shops replace both along with dryer, anytime a systems been opened, to avoid returns. Along with flushing the system, a must if a compressor goes bad. Otherwise evacuating and pulling a vacuum will only get moisture out, not contaminants. Contrary to the sound of pulling a vacuum. The vacuum process only raises the temperature inside the system. Causing any moisture to boil away.It doesn’t actually pull contaminants out.
     
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  9. Ridgeline

    Ridgeline Road Train Member

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    Second this, we went through a number of them a while back with this system, ended up having the system flushed out and replaced the expansion valve.
     
  10. AModelCat

    AModelCat Road Train Member

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    Gotta be a plugged up expansion valve. A/C is like hydraulics - can never be too clean.
     
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  11. w9l

    w9l Medium Load Member

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    Expansion valve is like a 50 or 60 dollar part at Fleetpride. Had KW change one out in bunk on my 14 last week and they charged me 104.00 Most common problem I can think of with KW bunk ac.
     
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