My system freezes up after 25 minutes of driving. Was just wondering what the other switch does? I think it's just a low pressure cutoff switch. It screws into the expansion valve. I've replaced the cycling switch and the new one seems to be working as it should.

 

Yes,that is the lp cutoff switch. The probe of the cycling switch could be mis inserted, too far in or out, I don't know. Also, i think that freezing is also a result of low airflow. Check your heater box, Mine was stuffed full of pine needles...Mark edit: check this thread: https://www.dieseltruckresource.com/...-twist-298318/

 

Hey thanks, my airflow is pretty good. I'm not sure if airflow makes sense either. One should be able to run the fan on low speed without freezing. Plus I've already cleaned out my heater box from both sides. I think this is going to be a pain in the **** for me to figure out

 

Check your probe and maybe you got a bad cycling switch. Where did you find it? The last I knew was a guy in Texas that had 2, he sold me one for around 30 bucks. Later on, a member here found him and he wanted a few hundred bucks (iirc) for the other one. There can only be a few things to cause this and lack of airflow through the coils is one. Maybe your evaporator is all cruded up internally...Mark One other thing, I am sure that the dodge engineers calculated for the low fan speed setting air flow to not cause freeze up if the rest of the system is healthy...

 

I found a couple on Ebay NOS. It seems to be working properly. I put a thermocouple near the tube. It turns off at 37 degrees and on at 43 give or take a degree or two. I get anywhere form 40-46 out of the vent. So fare the only options I can come up with is flush system or replace evaporator and condenser in case either is blocked.

 

Is it still the original r12 system? My compressor broke and I through in an all included (except evaporator and condenser) Chinese kit. I converted to R-134a and replaced all the hoses for around 300 bucks for all. Still blowing icicles after 5 or 6 years (7 years almost exactly). Here is a thread of what I did: https://www.dieseltruckresource.com/...m-t313221.html ...Mark

 

That's pretty cool Mark. I did buy a similar kit off eBay for my old Buick. Still sitting on the shelf. Just had my compressor, hoses, dryer, expansion valve done a little over a year ago.