Recently I noticed the air conditioner on my 2010 Ranger was seemingly stuck in the on position. When you turn the **** to just vent the exterior (ambient) air, the AC was apparently running. At one point the condenser froze over and air flow through the vents ceased until everything thawed out.

Is there a switch/relay/or other item I can check/replace to get the system operational again?

 

AC Compressor should be off when selector is on OFF, PANEL or PANEL/FLOOR

Either Defrost will turn it on, as will AC of course

Could be a problem with the selector switch with OFF, PANEL or PANEL/FLOOR selected

Is this what it looks like: https://www.ebay.com/itm/2004-2011-F...%7CMake%3AFord


The Computer turns on compressor when it gets 12volts from the selector switch
Computer uses the AC Clutch Relay in the engine fuse box to turn it on

 

Understood on when AC should be on versus off. In this case I noticed it was on when turned to the vent position (ambient air as I think of it). I wasn't thinking the switch was itself bad compared to other components, like relays, etc. If the relay fries could this technically leave the compressor always on?

 

Sure, you could pull out the AC Clutch relay, that will cut 12v from going to Compressor's clutch, so no AC

Then you could test its slots for GROUND from computer, thats how AC compressor is activated

Automotive Mini/micro relay pin layout here:http://www.gtsparkplugs.com/images/m...lay-wiring.jpg

85 and 86 are a relay's coil connections, when one is 12v and the other a GROUND then coil becomes an electromagnet and pulls the metal arm inside the relay down which connects 30 and 87 together, and that sends higher amp 12volts to the AC Clutch turning on compressor

So with relay removed, key on, test slots 85 and 86, one will have 12volts, thats from fuse #43 in engine fuse box
The other one will be the GROUND from the computer.

Test for GROUND, use Climate selector in OFF and then AC on, not sure if engine has to be running to do this test, but I think it does, since you wouldn't want AC Compressor ON during start up, so computer would disable AC Relay GROUND until RPMs are above 400 or so

If its a GROUND even when OFF is selected then wire could be shorted, switch in cab could be sending 12v to computer all the time, or computer itself may have a bad circuit


AC compressor is on to Dry the air in the cab to prevent windows from fogging up and to prevent "musty smells" in the interior
But compressor should cycle on and off when AC ON is NOT selected, it just keeps the evaporator cool enough to cause water vapor to condense on its surface and the water to drip out of the tube in firewall.

 

So, some photos. The compressor froze over solid. I pulled the fuses and relays for the ac clutch and I am wondering if the sensor i am pointing to is the culprit. What part is this?

 

Thats a pressure switch, no not the problem

The are two pressure switches, high and low
If the system has a blockage the pressure can get too high and one of the connections with blow apart, weakest one, so any ones guess, lol, but not a good thing
If pressure gets too low then compressor can run out of oil and burn up.

So pressure switch is there for safety, icy cold is what AC should do.


Icing like that shown can be a few things, but not related to the compressor

It sounds bass akwards but LOW refrigerant can cause icing, cooling is based on the Expansion of the compressed refrigerant, if system is low on refrigerant then it expands TOO MUCH and cools too much which causes icing

Air flow thru evaporator warms it up to keep it from icing up, if air flow is blocked then icing starts
So does blower air flow feel strong on high?

Moisture INSIDE the system
Any time AC system is exposed to outside air you should install a new receiver/dryer, this traps the moisture in the to prevent icing on the inside AND outside
When AC is on does it sometimes cool less then come back cooler, then less then cooler, that could mean internal icing

 

When I start the truck up cold, things run fine but then the air flow becomes less and less and then there is no air flow through any of the vent settings as the compressor ices up. On AC and Max AC, the air is NICE and cold. Cold is never an issue...but if not enough R-134 I can understand why the condenser might be icing up. I can certainly grab a recharge kit and top off the system.

If there is water in the system, where can one drain it out?

 

You don't drain water out, you replace the receiver/dryer, so system needs to be emptied and then refilled

Is the AC compressor still on all the time, thats a problem as well