Western star 4900 2014

Why would you want to blow clod in the sleeper. At least get him a hotel room first...


Sorry, just couldn't resist.... Now for an actual answer..

Assuming you have checked the blower air filter, it is clean and air is flowing well from the vents but it is just not cold enough..

Is the dash air conditioning considerably colder than the bunk air or are they both not cold enough?

If both not cold enough, you may have a weak compressor, be low of freon or both.

If dash is cold but not bunk you may have a bad or dirty expansion valve (or orifice tube - you should have 1 or the other depending on the way your system was designed.) You should have one for the front evaporator and one for the back evaporator.

If both dash and bunk are not cold and you have confirmed your compressor is good and your freon charge is good it may well be a common design problem.

When the factory designed the A/C system 99% of the time they select a compressor and condenser adequate to do the dash air. Then they go and add a bunk unit which really means they need a higher volume compressor and additional square inches of condenser surface area to properly run both the dash and bunk evaporators.

Frequently the compressor is at least acceptable to do the job but the condenser not so much.

On my truck this was definitely the case and I have seen it on several other trucks as well. Keep in mind I'm in Florida and I hate to be warm, much less hot so I do everything I can to maximize my A/C system.

So, what do we do to fix this problem.of not enough condenser? The answer is pretty simple and while not cheap it is not really all that expensive either, especially once you feel the results.

You need a larger and or more efficient condenser. Problem is the one under your hood is probably as big as it can be given the under hood space available. It is also located basically in the engine compartment where it get hot. And in the summer really hot.

Solution? 2 choices. Remove the factory condenser from under the hood. That will allow your entire engine compartment to run a bit cooler (side or bonus benefit) replace the condenser with a extra large remote mount unit with dedicated fan(s). A company called Red Dot makes systems and components for military, mining and construction equipment. It's all heavy duty stuff and fully up to the over the road trucking environment. They make units designed for mounting on the cab roof or a vertical back wall. In fact a lot of the APUs you see with the small radiator looking thing on the back of the sleeper is actually a Red Dot brand condenser and fan unit for the APU a/c system.

You can also leave the factory condenser in place and supplement it. The a/c shop can cut the output line of the factory condenser, run a new line to a small (like the APU size) condenser/fan unit and back to the front to the factory plumbing that you cut at the output of the factory condenser.

This now has the freon run from the compressor to factory condenser to new added condenser and then back into the normal circuit.

This allows the factory condenser to try to cool the freon and the new added condenser to really cool it.

Your a/c is all about heat transfer and the more you cool the parts of the system that need to be cooled you give that much more room for that much more heat to transfer.

While you have the system open you should replace the dryer as well. A better and usually less expensive option than messing with the factory dryer is to purchase and install a separate stand alone dryer. Your a/c shop will have them in stock and it is a simple matter to add one into the new lines they are installing.

Total cost for a job like that is usually about $300-600 depending on the exact components you use and who does the work.

Does it work? In short yes. On a 97 degree day on Florida I had 47 degree air blasting from both my dash and bunk at the same time. Worth $600? To me ... YES. All summer long.

As a side note, you can shut off the water flow to your dash and bunk heater. Eliminating that heat from under your dash and under your bunk will help a lot.

I installed 3 valves to do that. 1 valve in the from engine to heater line and 1 valve in the return. I also added "T" in each line between the engine and the valve. Tie the 2 Ts together with a valve. This third valve and the TS allow you let the father still pump out of the engine and back into it without going g to your dash or bunk. That removes any potential issue with any possible problem arising from simply stopping that circulation. Your engine may be fine with simply blocking the lines but the way they design stuff these days, why take a chance?

 

On my 4900, there's a cheap plastic valve on the firewall that opens for heat, and closes for AC. It's connected to a cable, which goes to the HVAC controls. The valve has a habit of leaking internally, and blowing heat. Mine is a daycab, but I'd imagine there would be a similar valve for the sleeper controls.