06 M1165 AC Issue

[Nethawk86]

Just picked her up. Owner said he never messed with the AC but when he connected the 3 wires under the passenger side dash and turned the key, it started smoking, so he unplugged it. Vehicle is in very nice condition, and besides a very hard shifting transmission from 1st to 2nd (will figure that out next after fluid changes), its killer! I took off the dash vent shroud cover to repair all the heat cracks in the plastic (since everyone wants $700+ for it) and figured id try and see myself what he was talking about. The 3 wires only connect 1 way, so there wasn't any chance he connected something wrong (which he did with the tail lights when he upgraded to LEDs). Factory AC, 6.5 Turbo Diesel, 4L80E.

Plugged them together, turned the truck over into RUN, not starting the engine. Then flipped the fan switch to High and I could hear the fan pulsing a few times before smoke came out followed by a "PFFFFT" sound. Smoke was definitely electrical in smell. Immediately turned off and let it sit for a few minutes. Checked over everything and nothing seemed burned on the outside (but will check thermal next). Unplugged the wires, turned the vehicle back over to RUN again and flipped the fan switch to HIGH and then LOW. Both working fine now, not pulsing or anything. So fan/blower motor works fine when not connected. And the smoke/sound came from the unit under the passenger dash where the blower motor is.

 

[DREDnot]

How was your rear AC evaporator/blower box acting during all this?
What were the numbers on the metal tags on the wires you were unplugging?

 

[Nethawk86]

Honestly, I didnt even look/hear/feel what the back box was doing. I was focused on making sure the front didnt catch fire....darn. Tags are 435 and 438

 

[DREDnot]

Those go into a small black box on the side of the evaporator assembly, correct?

That is the "temperature switch" that senses if the evaporator core ices up and shuts off the compressor till it thaws out. The two skinny white wires are for the temperature probe.

When the wires are unplugged the fans (front and rear) run, but the air that comes out is not cold because your compressor is not engaging, correct?









If you plug the two wires 438A and 435D together it effectively bypasses the switch and your compressor should kick on and make cold air.

 

[Nethawk86]

plugged them into eachother and I started the truck. Heard the fan pulsating again, and the smell...but no smoke, so I think the smell this time was just residual in the coils. Let it run but never got cold. Flipped over to heat and it heated fine. But no AC, and the back box wasnt working at all. Let it idle for a while and never got cold. So maybe low on freon....or whatever smoked....is finally dead after doing it twice now lol. I did leave the temp probe connected

 

[Nethawk86]

Ok, so, the electric water shut off is busted, the thermostat seems to have been what smoked...I unbolted it and either something blew from the inside of the AC box..or...the thermostat blew itself. Then, I pulled codes and got 22 and 38.

 

[DREDnot]

The broken hot water shutoff valve is a common ailment. Most folks replace it with a 1/2" ball valve with 5/8 hose barbs to manually shut off the hot water when not needed.



The temp switch that fried can be replaced. Avoid the older model with the white label and find the newer model with the tan label. Hopefully the thermo bulb in the evaporator core isn't the cause.



Where did you pull codes from?

Was your compressor clutch engaging?

It could be out of freon like you said. You could put gauges on it if you have them or take it to an AC shop to get it vacced down, leak checked and recharged.

 

[Nethawk86]

The broken hot water shutoff valve is a common ailment. Most folks replace it with a 1/2" ball valve with 5/8 hose barbs to manually shut off the hot water when not needed.

View attachment 955736

The temp switch that fried can be replaced. Avoid the older model with the white label and find the newer model with the tan label. Hopefully the thermo bulb in the evaporator core isn't the cause.

View attachment 955737

Where did you pull codes from?

Was your compressor clutch engaging?

It could be out of freon like you said. You could put gauges on it if you have them or take it to an AC shop to get it vacced down, leak checked and recharged.

I pulled from the TCM system shorting A and E and reading the trans code. I think the compressor was because when I turned it on AC the vehicle RPMs and sound was "pulsing" whereas before it just ran without any difference in sound. I have some guages, will toss them on and check.

What's the purpose of the flow valve? And doing the ball valve mod would do what? Im in AZ so it only gets cold here for like 3 months. If it'll save me the $220 for a new flow valve system and doesnt really effect anything, im all over it. Hopefully between the temp switch and flow valve, the back AC box unit will kick on also. No idea also how to get what looks like the ground wire to it off....it looks to go inside the evap unit itself.

I do have a dripping and leak at the below part and im not sure what it is. I cut the end of the hose as it was frayed and reinstalled, but still getting a drip at the clamp. Then around the bottom bracket for it where the bolts are, the gasket sealer looks to be coming off and it seems like oil is leaking from there.