What I did to get ice cold air in my ProStar

If you have a ProStar, you know the problems. If you have not experienced this, you are lucky. This is what I found messing with mine for several YEARS. Yes, years, replaced everything multiple times, but last year I did something that has everything working, finally. Then I stumbled upon something else that has it making snow in the cab.

There is an "Ambient Air Temperature" sensor that you need to find. This sensor is the one that reads the outdoor temperature, if like my truck, it reads all over the map. If 60* outside, it will read 100*, -20* it will read 40* and so on. This temp sensor controls more than just that thermometer in the cab, it is also tied into your AC system.

Mine was located in the wiring harness on the driver side. This is the harness that has your headlamp wiring in it. It is located under the radiator under twenty yards of tape and split loom. Dig that thing out, pull the wiring out as far as you can. There is a clip on this sensor, you may have to splice in more wiring to place it where it needs to be. I clipped mine up on the plastic windshield wiper cowl above the door hinge on the driver side of the truck. Since doing so, the AC has worked.

Now, what I found to get the AC below 40* F was to drain the AC system, vacuum it down, and replace the R134A with straight R134A, NO DYE! That dye just messes up that system, since removing the dye, the AC now makes ice cubes.

This is a simple fix, dig out that sensor and install straight R134A refrigerant. It beats throwing parts at this system and it fixed my years of issues.

Also, make sure your valve to the heater core, that one under the hood controlling coolant flow to the heater core is turned off. Especially if you are running in areas with high temps, like down south. This is such a crappy design, this AC system, that many of us have installed a solenoid to turn the heater core water on and off inside the cab. Wire this selonoid in and install in line where the shut off valve is. If you do not have a shut off valve, this will go on the heater core input heater hose. Wire this to a switch in the dash. That way, when the AC is freezing you out, say like at night when things cool off, you can flip a switch instead of stopping, opening the hood and turning on that valve to get some heat in the cab.

Here is the solenoid https://www.amazon.com/gp/product/B01M2WZ35V/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

 

Lucky guy!

 

I don't know, I have more than a few friends with both, their problems dwarf mine in regards to the body. I'll stick with my very well known quantity, the ProStar. They are no better or worse than the other guys, an EPA truck is an EPA truck, no matter whose badge it wears.

 

Do you have a turbo and an EGT (Pyrometer) gauge? And I am assuming a Cummins. Where are you running it going down the road? The best fuel economy for these motors is right at 1650 rpm. And have you done an EGR tuneup? How about the emissions, still on?

 

Nope, I used to think the same... 1650 is the magic number. I just in framed mine, and have been driving it at that 1650 rpm with my 3:42 gears, 18 speed. Long story, prior to the in frame, I was at 7 mpg BOBTAIL heading down to GA to do this work. 800 miles on the in frame, and I'm at 11 mpg on paper, the test will be with the dry van.