09 prostar a/c replaced everything still not working

Usually if you have to cycle the key to get it to work temporarily it is seeing too high of a/c pressure. This resets after a key cycle. Have you tried a pressure sensor yet? Check the sensor connector and pins for any corrosion.

 

Hi to all, I too am having issuses with the AC in my 2010 Prostar w/Cummins ISX 435. This is my second summer with this truck. I noticed last summer the AC wasn't that great, and so far this summer it seems worse. I made the mistake of buying a can of refrigerant w/hose on the road, hoping the system was just a bit low, but realized the fan was running too often after adding it, and bled some back out, enough to get the fan back to a normal state. Finally was able to get a gauge set on it during some hometime, Here's what I came up with.
Ambient temp was 77 on a partly cloudy day. Static pressure was 84psi, a bit low but enough to test the system. Started engine, turned both fans (main and bunk) to high, and selector on MAX AC. Gave it a few minutes to stabilize and observed the high side gradually build up to 320psi at which point the fan clutch kicked in. the pressure dropped quickly to 250psi then slowed in it's decent to 170psi where the clutch fan kicked off. (about 30 seconds total run time on the fan) The pressure once again slowly build up to 320psi (about 90 seconds) then the cycle repeated. Meanwhile, the low side never dropped below 42psi. Should be closer to 30psi so my brain is telling me I need an expansion valve. But I've never seen the high side swing so much. I'm more familiar with car AC's where the pressure is in a tighter range, and the compressor clutch cycles on and off instead of the cooling fan. I would think that moving down the road, the air flowing through the condenser would keep that range much closer. But I thought I should get some advice before taring anything out. I'm also thinking, if the condenser were clogged, it wouldn't drop to 170psi when it's cooled down by the fan. It would tend to remain high all the time.
BTW! the compressor clutch was engaged the entire time I was running the test.
The air temp coming out of the vents in cab is no more than 10 degrees below ambient air temp. (at idle) In sleeper it's about even. Like no cooling at all. I believe it has a seperate evaporator w/expansion valve? Is this also part of the "no-idle" climate system? That seems to work better. After the engine is shut down, I'll turn on that AC system, and after 10 minutes, it starts crancking out some pretty cool air.
Any advice will be greatly appreciated.

 

Low side pressure will be higher when it is still over charged, or has excessive air in the system. A dirty cab filter will restrict air flow over the evaporator and cause lazy temps. Right now your biggest problem is the guessing game with the actual charge you have. I recommend to have it properly recovered, check for leaks, and recharge it.

 

You get your a/c working yet? If so, what was the issue?

 

The blower should have power running to it pretty much directly from the fuse box. check for power at your blower motor plug with your test light. If you got power there then it is a control circuit issue and not a power supply.

The blower motor is on a ground switch circuit. The hvac control sends signals to the resistor (crescent shaped thing with spikes on it) and then it provides a predetermined amount of resistance to ground. It shuts the blow motor off by telling the resistor to max out resistance and absorb the 12v coming to the blower motor.

I would also check the resistance of the resistor. The circuit are grouped in pairs on it. it has two thin pins and two larger ones. I don't remember the specs but the middle larger in has real low readings on the thin pins compared to the outer pin. (should be relatively close to each other one big pin going to each smaller pins)

Those go bad and short out creating so much resistance that the blower never turns on. Or enough heat it fries the wiring or connectors (usually will darken whatever pin is getting the hottest). If your truck still has the silver breaker style fuses, check the resistance of that as well. When a circuit fails, those sometime will blow, then fuse back together, and never blow again. This will pass checking it with a test light and have you chasing your tail (speaking from experience, i have come to despise those fuses)

International made it kinda nice converting the hvac systems to all the same between nearly all the series now.

Oh yeah, also if your fan never shuts off...this is likely the cause. It will also go bad and not create enough resistance to shut the motor off.

 

Hello? Is this thread still up? 1st seat driver 90days now & my '14 a/c was just overhauled after numerous dvir's but ofcourse now im back down south... blowing hot again. Anyone get a true fix? Final cost? Locations?

 

Explain what all was replaced....Thermistors and expansion valves used to give tons of problems..
Is the lines cold where it goes up to the fire wall? Compressor running?

 

I encountered a stupid Prostar AC problem today in shop.
AC blows cold in sleeper but not in front cab.
Replaced the cab expansion valve.
Checked the motor under passenger dash made sure it closed and opened.
Had to replace the other motor because it was broken and stuck on blowing at the windows.

I thought both pipes were cold where it goes in the EVAPORATOR CORE because of the expansion vavle. And I know one should be cold other hot. Just like under the sleeper. Changed the expansion valve and no luck.
Tomm. I will be replacing the filter between the fire wall.

Any one know what else might cause this?

 

A lot of those actuators break between the actuator and the door flap for the temp. You need to remove the actuator to check for this.