Sleeper AC ducting...

[Waterloo]

I have been tearing apart the sleeper over the past week, new cabinetry, flooring, etc... Well, I got under the bed in the ProStar and found so many damn AC duct leaks I about fell over. I would suggest getting under the bunk and feeling around for air leaks in the duct work. I used the aluminum duct tape, the same stuff you use on your home HVAC duct work. It was not difficult, but I am glad I got under there to really inspect.

Just thought I would throw that out there, especially if you own an older truck like I do.

[LRT1549]

From what I've read on this forum about those Prostar AC's you need all the help you can get.

I don't know about the Prostar's however for anyone that has an older Paccar product I would suggest cleaning the bunk heater/AC unit at least yearly if not By-annually as they do not have a filter on them and being under the bunk and the fact that the seals on those doors don't work worth a damn, they get a lot of dust under the bunk and that crap is pulled into the HVAC system.

Now I've had several KW's and my newest one was a 2014 so I can tell you up to 2014 anyway that all the bunk HVAC units are pretty much the same. I have found that they have a gap between the case screen (for lack of a better term) and the AC exchanger. This gap is not covered by the lid to the box and at first glance one would think that there is a filter cartridge that slides in there.... There's not. However I have found that CAB fresh filters, the ones you see in the dealers and some chrome shops with the Yellow insert in the plastic case, They sell them both with the black plastic case with the filter inside and then they sell the filter elements separately as well, The cab filter for a Pete 379 will fit with just a little trimming. I have also bought a standard home HVAC filter and cut them down to filter that air and keep the crap out of the AC exchanger.

Now on any narrow cab KW there is no filter on the cab HVAC either. The inside air is brought in through an opening at the top of the HVAC box behind the glove box and ti next to impossible to get to without removing the hole damn blinder box from behind the glove box.

I have tried to make a filter inside the core box several times but they all failed, one even took out the blower motor so what I do is open the box twice a year. When you open the box the blower comes out with the lid. Look in the box and you will see a long opening the width of the box at the top rear of the box. This is where the cab air enters the box. If you look into that opening you are looking at the back of the blender box inside the cab.

You will also see one of Paccar's famous "Piano" motors that has a rod hooked to the fresh air vent on the side, and a little silver thing with a probe and two wires hooked to it.

Remove the rod to the fresh air vent, unhook (lable one first) the wires going to the probe, and remove the screws holding the plate this all sits on. remove the plate and block the hole going onto the cab then use a presser washer to clean the AC exchanger and heater core. Be care full when removing the plate as the probe goes into the AC evaporator but it just pulls out, be sure to replace it where it was as this is what controls the temp when you select a temp on the HVAC control inside.

When you look at the box you will see there is going to be a gap where the fresh air tube comes into the side of the box. (I haven't found one yet that don't have a gap) I use that silver HVAC tape (Not regular duct tape, as that works on anything but a duct) and seal that gap as best I can to keep dust and dirt from the engine compartment from entering the system. Then again when I put it all together I use this tape and seal the box cover all the way around. This system has a fresh air vent on it but the way they built the box is a joke cause its not sealed and even when you close the fresh air on the controller the box is so poorly sealed it's a joke. You drive through a dirt parking lot and the engine fan comes on and your nice clean HVAC is no longer clean... DON'T forget to unblock the cab air inlet before you replace the lid...

I also have someone run the blower control through all four settings while I am holding the lid/blower in my hand to verify there are four different speeds before I but it back together. These blowers are notorious for losing a speed or two..

[Waterloo]

I just took a run in her tonight, man she is blowing ICE COLD! And lots of COLD AIR, now that the leaks are fixed! It was already to the point of unbearable, the cold AC, now I will be the guy wearing the flannel in Phoenix, In August. ;-)

[dhirocz]

I went and resealed mine, and it made a world of difference in the air quantity in the sleeper.

Next up is for me to insulate key A/C lines to keep the system cold, and I need to investigate some leaks at the front A/C box for the same reason, low air quantity. Based on the frosty windshield I get sometimes, I'd bet I have a hell of an air leak in the dash.