Evaporator freezing
 

What are the possible causes of an AC evaporator freezing up? I'm using propane.

A bad low pressure control switch can cause this.

Why Are You Using Propane???????

Charge might be low, not sure, the PV charts are assuredly different.

how is the propane working i was gonna try it but mine never went low this summer

Make sure you mark system VERY WELL. A friend of mine spent a couple of months in the Chapel Hill Burn Center because someone charged an AC with propane and he did not know about it and the unit exploded in his face due to a leak and a spark from a relay nearby. He is permantly scarred because someone wanted to save a few dollars! If you get a leak inside of the cab, you are going to light up like the 4th of July if there is a spark! Propane is heavier than air, so it will pool around your feet before you know it. If you filled it full, you already have a leak somewhere. If you are interested in saving money with the AC, OPEN THE WINDOWS!

evaporator freezing
 

I didn't mean to start a propane discussion thread, there is already one for that. I am just looking for possible reasons why the evaporator will freeze. Any other suggestions?

Does it drain? A plugged drain will cause it to fill up and as the condensation freezes and starts to plug the evaporator from the bottom reducing airflow through it, the evaporator gets increasingly colder causing it to freeze even faster. You should aim for a duct temp of around 40 deg, any colder and you risk the core freezing up.

Three most popular reasons for evaporator freezing up:

1 - low pressure switch not operating (located on drier)
2 - low freon (wasn't properly charged or has leak) these systems can handle as much as 50-55 on low side.
3 - Reduced air flow through evaporator (blend doors, dirty, etc.)

evap
 

woah, 50-55 psi? I have max 25 psi on low pressure side. Drain is free and blend doors are working. I cleaned the entire heater box out when I replaced the core and evap. I'll try to put in a bit more on the low pressure side.

I was having problems of cooling great when at idle or creeping around town, but as soon as I hit the road, air temperature would rise coming out vents. I visited my local AC shop and told him what it was doing and that I was running around 35psi on the low side and he told me to bump it up to 50-55. After doing this, AC will freeze you out going down road at 55mph. Keep in mind I did this in 90+* heat, so if you are in cooler ambient temp, then don't go as high on pressure. 25 is definitely low, you should have 35 on a warm day. It helps to also monitor high side as this will let you know condition and how well compressor is working.

Guys, re-read his post, he is running Propane for his charge.

Someone who runs Propane needs to give him his pressures.........