Hi all you suffering 3500 van owners. I'm a retired tech who did a favor for a friend, and it led me down this rabbit hole that went past you guys. Please forgive me if this is old news, I subscribed just to tell you what I found in hopes it helps someone.
3500 van, early-mid 2000's, gas v-8 (sorry-don't have exact spec's), built for sale in Canada,(we in PNW), A/C stopped blowing cold. Diagnosed as discontinued part # 55035447, AC cycling switch, located in fins of evaporator. I got hold of a very hard to read wiring diagram, and was able to determine this is part of a convoluted ground control path for the AC clutch control relay. Of the 3 wires at the sensor connector, one was "hot key on" (center, white), the other 2 are part of the ground path. I connected the 2 outside wires (do not touch hot wire, may damage ECM), clutch began cycling, friend's wife is happy.
I'd like to note that while the AC is blowing "cold enough", diagnostics indicate it is low on freon. I don't know if a full load will freeze the evaporator, don't want to find out. Freon is very hard to get($$$), friend is happy.
I used a heat gun to open this sensor, and I found a tiny printed circuit board with an IC chip and other tiny electronic parts. My camera sucks, this is my best shot. I hate when manufactures do stuff like this to us. I hope this helps someone.

sensor 55036447

 

great info!

So, just grounding the two bypasses that sensor switch? And you just disable (tape/heat shrink) the white wire?

Just wanted to clarify

Also, how do you get to the evaporator? I have an 2002, it looks like the top of the case comes off, but I havent tried yet

Thank you - great post!

 

You do not need to do this. See wire harness coming out of front of box, follow that to a connector on backside of radiator support, behind headlight, repair happens here. 1 wire (test van-side connector, not sensor side) is battery voltage when key-on, another wire is battery voltage coming from ground side of the coil that is inside the A/C clutch relay(unplug relay while testing), 3rd wire continues ground path for relay. It goes bat volt key-on to relay coil, other side of relay coil goes to ECM, then hi-pressure switch, evap sensor, low-pressure switch, control switches on dash, then to a common ground. You could cut wires on sensor side of that connector, seal hot wire, connect other 2. Good luck.


opened about 1.5 inch in front, all but screws against firewall

easily pulls out

 

Can u tell us the vent Temps they are getting with this fix you figured out. I get almost no cooling at idle. It gets slightly cooler at 70mph speeds. But seems like it's not cooling the maximum. Altho my compressor does not have an issue cycling. I believe it will stay on for a long time then shut off. Does this bad sensor shut the compressor off prematurely before evap reaches 38°F ? I think mine is working good, but if it's part of my problem I need to fix it asap. I'm also thinking my expansion valve could be bad or I have an over charged system. Is it possible to see 38-43°F Temps blowing from vents in these 3500 vans? Thanks in advance for the post here!

 

97St.Wagon3500. The are many variables that can affect vent outlet temp, and your degree of satisfaction with it. I have measured 32*F at vents on this version of A/C in vans/trucks I have repaired, I have also measured below 35* on A/C systems that did not feel like they worked at all. During my 50 year career I found customers were happy with vent temps as high as 50*. High humidity really kills A/C effectiveness.
You really need to start diagnostics with pressure readings, and a strong understanding of A/C theory. Pressure readings was the first thing I did on the 2001 Ram Van 3500 Bus, 5.9 gas, front & rear A/C that I got working last month, measured 45* at dash vents when working. The system is low on freon, family does not care, 10 kids & wife happy after a year without. I'd like to top off this system and see if the evaporator freezes, but I no longer have access to freon.

 

Boy this site is frustrating, 3rd time I have been logged off in the middle of a reply, lost my first 2. Good luck all, I'm out.