Where the heck is the AC thermostat?

Wallace bros · Mar 9, 2019

CondoCruiser said: ↑

Most vehicle AC systems the compressor cycles automatically. Temperature is controlled by fan speed and adjustment of the blend door via the temperature switch. The device near the blower motor is a resistor block.

Do you adjust temperature with a dial or slide or do you have a digital temp display with buttons?
Click to expand...

Wallace bros · Mar 9, 2019

I have a nob

Eddie1 · Jul 3, 2022

droy said: ↑

Sorry, my bad;
KW invoice actually labels this as "Item # 002P/BD13550 Switch-Freeze Control". It is a rectangular metal/plastic gizmo about 1 1/2" by 1 1/2" by 1" has two male blade electrical connectors, and about 12-15" of thermocouple/thermostat type of approx 1/16" tubing with a red tape stripe that I'm assuming is a depth marker. Opposite of the tubing side, a clear plastic snap on type of cap protects a wire wound to look like a small coil spring. The top (I think) opposite of the electrical connector side has an opening that is covered with silver foil looking tape. Removing the tape shows the top of the coil of wire with an adjusting screw head that is painted with tattle tale paint.

My 2004 W900 had a thermostat, IIRC, but I think those year models used a different type of blend system to control the temps. I replaced the thermostat on it, putting in an adjustable one, and I guess I mistakenly assumed that is what is in my T800.
I asked for the thermostat, or whatever the newer style KWs use, relaying my conversation with the KW tech I had cornered outside on an earlier day. Don't know why neither the tech, or parts guy didn't correct me- apparently others use the wrong term enough that the KW folks know what we are referring to.

Reading the replys (and thanks), I don't think I have Climate Control, just the standard system. The center knob I thought was the thermostat is more than likely the temperature control knob, has the blue to red adjustment indicator.
AC relay in the fuse panel has been replaced twice, refrigerant level checked many times, I have a set of gauges, and have asked a couple of guys to double check behind me. Sticker on side of radiator calls for 4 lbs, whenever I replaced my compressor, I pulled a vacuum, added the 4 lbs, then made a note of where my gauges were reading. Did seem a bit low on the low side, 20psi, and normal on the high side around 150psi. I have an AC trouble shooting book, and noted the readings in it. After the compressor replacement, even with the low side @ 20 psi, the AC worked great, until I went down the road then couple of hours later it began it's cool/no cool routine. I'm no AC whiz by any means, and welcoming any tips you'll can offer, but I keep wanting to go back to the fact that hitting a bump in the road will sometimes cause it to:
(1) Stop blowing cold air; lately with ambient temp in the 90*s, it will blow about 60-70* out of center dash vent sometimes, sometimes it will blow hot air. Normal is 47-49* in center vent.
(2) At that time, the AC blower fan will barely push air out the vents. I also keep the fan speed knob on the second setting, low does not seem to push enough air even when working correctly. Whenever the system decides to start cooling again, the fan will start pushing air out the vents as if you turned the switch to a higher speed.
Maybe I'm pulling at straws, but for both those things to happen at the same time, leads me to believe it is the switch group, which is integrated. Tech, and parts guy both commented that the switch group will short, and have symptoms similar to what I described. Was told you have to replace the whole 3 knob group, can't replace just one switch.

Sorry for the ramble, and thanks again for the help.
Click to expand...

Eddie1 · Jul 3, 2022

droy said: ↑

2007 T800
AC sometimes works, sometimes no worky;
Hitting a bump will sometimes cause it to quit cooling, then later back to normal. Also, whenever the AC goes to no cool, the AC fan will barely put out, no freezing around expansion valves observed. Any adjustment of the thermostat knob, fan speed switch, cutting off sleeper air at the dash panel will almost always put it in the no cool mode- when it is working, I cannot adjust it!

Checked, double checked, triple checked wires, and plugins @ binary switches, comp, etc., Replaced compressor, both expansion valves, and drier/filter. After that didn't help, took it to local dealer, explaining the problem. They replaced both expansion valves, drier/filter, and a hose they claimed was seeping. Big surprise, them replacing the stuff I had just replaced did not solve problem, only made wallet $1000+ lighter.
Caught a helpful tech outside of another shop who listened to my story, said his guess could be thermostat, ($44); but more likely the three knob AC control panel in dash ($640).
Going to R & R thermostat, but pretty sure that it is not expensive enough to be the problem.
Click to expand...

sir , did you find out the problem, im going thru rhe same exact problem ive done everything you did and still no ac, well only when it decides it wants to blow cold
Please get back at me with any advice 956-607-2329 ( kw t600 2007)

Eddie1 · Jul 3, 2022

any one fixs this problem

Eddie1 · Jul 3, 2022

help!! ive done everything mentioned in Droy's post, any one find the issue

Worzely · Aug 28, 2023

Have 2000 classic xl..freeze switch does not cut power to compressor...compressor runs all the time and when I n high humidity the lines and compressor and compressor head freezes untill it blows a line!! Unplug switch and compressor shuts off.. wont show up if at idle, but 1000 plus rpm will freeze in several minutes! Picking up new switch from dealer in am. Parts dept didnt even know about the switch, but had one ordered for next day ..

Rideandrepair · Aug 28, 2023

You mean the high/low pressure switch on the air dryer right? That’s most likely the problem.

Log in or Sign up

Forums

Find Trucking Jobs

Where the heck is the AC thermostat?

Wallace bros Bobtail Member

Wallace bros Bobtail Member

Eddie1 Bobtail Member

Eddie1 Bobtail Member

Eddie1 Bobtail Member

Eddie1 Bobtail Member

Worzely Bobtail Member

Rideandrepair Road Train Member

Trucking Jobs in 30 seconds

Wait, employers can't reach you!

Log in or Sign up

Useful Searches

Find Trucking Jobs

Where the heck is the AC thermostat?

Wallace bros Bobtail Member

Wallace bros Bobtail Member

Eddie1 Bobtail Member

Eddie1 Bobtail Member

Eddie1 Bobtail Member

Eddie1 Bobtail Member

Worzely Bobtail Member

Rideandrepair Road Train Member

Wait, employers can't reach you!