Carrier APU question

Look at the under bunk unit. The corners are not air tight and there is a gap between the air intake and the vent under the bunk. Also, when they get older air leaks can occur around the cable bundle coming in from beneath the cab. All of these things cause the heater (and the A/C in summer) to have poor air recirculation. Basically, you are heating cold outside air instead of reheating warm inside air. Duct tape on the corners helps. Re-siliconing the cable bundle may also help. Making a little box plenum to seal the gap between the air intake and the under bunk vent also works wonders. Oh, and of course you need to wash your air intake filter every now and then.

 

I have a carrier comfort pro. Its in a cascadia evo. The sleeper is insulated and has the insulated curtain to separate the back from cab. Its minus 20 this morning and its comfy in the sleeper. I run mine in continuous mode when its this cold and use high heat setting. It maintains 72 in the bunk which is where its set. Also running constant my oil temp is 75-80 degrees and coolant about 105 every morning when I turn the key. All temps listed are Fahrenheit. Truck starts just fine. My advice if your heat can't keep up close the curtain so only heating the sleeper when you go to bed. Cab don't need to be warm if your not in it...

 

Actually, that's a lot of heat for a cab. Those units HAVE to be sucking in outside air somehow to not heat that space well. A lot of HVAC systems are required to bring in outside "ventilation" air by various codes. Check and see if the circulation system has a vent leading from the outside somewhere. Maybe there's a setting for "recirculate". Figure out a way to reroute the air system.

3000w x 3.412 = 10236 BTU's, that's enough to heat a 20ft. camper, nevertheless a truck cab. Something has to be squirlly about how these units are installed.

I will be interested in finding a used APU at some point in time, so I get interested in these types of reports.

 

I have a new ?
My 2015 carrier with 8000 hrs on it has developed a quirk .
I maintain this thing religiously right down to keeping the housing and engine washed out every few months and it's been trouble free till now .
Last week it started shutting down randomly without throwing codes to the module in the engine housing...just a message on the control panel saying " check apu engine " , then it will restart over and shutdown over and over .
I replaced the water temp sensor and plug to no avail ...generater and alternater are fine ....all the connections are clean and tight .
This happens intermittently and after driving again and parking it may work fine for a while .
What would you check next ?
I haven't checked the oil pressure monitor yet and does anybody know where it is ?
Thanks in advance.

 

Brad, had the same problem. It was an air bubble in the coolant line. After my steer tire blowout last year I lost most of my coolant, filled up coolant and the apu was working fine for a while and suddenly it shut off all the time. Mostly after running for a few minutes when the water got hot. Was at MCT in Omaha and it took a while till they figured out the problem. They were bleeding the coolant lines and the apu was running perfect till my truck was sold. This could be your problem after the overhaul that there's some air in the coolant line to your apu.

 

How the hell you been Tom!?
That makes sense cause the day before this started Morehouse had the coolant lines to my after treatment system off .

 

Was very busy the last months and not really active in the forum.
When I had the blowout it ripped off the coolant line to the aftertreatment system.

 

You are the man Tom ! ....just goggled it and there is a purge valve on the thermostat housing .

 

I think when hot air reaches the temp sensor the apu shuts off. Sometimes without showing anything on the display, sometimes just check apu engine. Not sure if you can bleed the lines yourself or it must be under pressure.