tech2

you just said the evaporator was frozen...these are 2 causes for that. good luck to you

ian1035nr

How so? The evaporator is covered in ice. If there was no refrigerant circulating it wouldn’t get cold enough to freeze the moisture in the surrounding air.

Think of it like the frozen coils on a fridge or dehumidifier. They can’t freeze if they’re not running.

tech2

just because the evap exterior freezes doesn't mean the refrigerant inside isn't circulating...the refrigerent is always a liquid or gas. think about it....if the evaporator exterior is frozen over...no air flow to your vents as the system puts all hvac air thru the evaporator then to the heater core....the evaporator is never bypass thru design of the hvac case.

ian1035nr

I understand that. I’m not saying the refrigerant itself is frozen.

What saying is the air is ALWAYS cold when the A/C in on. And the clutch isn’t disengaging anyway. So any notions of the compressor kicking off and causing the problem can already be discredited.

Physically there is very little air coming out of the vents. This is an airflow problem. Not a temperature problem. And this only happens AFTER the A/C has been running for a while. Air always passes over the evap core before going to the fan. If the core is covered in frost/ice that built up while the system is running, then less air can pass between the fins and get to the fan, which in turn limits how much air is getting pushed out the vents.

Google frozen evap cores and reasons will generally be as follows:

1. The core is covered in contaminants like dust which are retaining moisture

2. There is a refrigerant leak

Those are the causes of an evaporative core freezing over. The compressor simply isn’t part of the equation here.

tech2

if you have a cycling clutch system the compressor must shut off to stop evap freezing. if you have a variable displacement compressor the compressor will run all the time but must switch off if the psi pressure sensor is below 27psi...
you said you have freezing evap AND if the comp doesn't cycle off you will get freezing. We both agree air can't flow thru a plugged core

an ac leak will block off air flow if; dirt forms on the pag oil but this will not be intermittent. So low charge or leak is not consistent.
ice formation will be intermittent.

if the core is freezing due to ice build up on contaminants...put the afterblow feature on...its designed to stop evap freezing...maybe you could google it