I'm here in southeastern MI, and have just turned on my 4 ton Earthlinked DX to cooling mode 2 days ago. When the compressor turns on, the temperature drops to the low to mid 50 degree range when measured at the plenum. After 30 minutes or so of the compressor running, the freon in the system seems to be freezing up in the compressor, heavy frost forms over the 3 "spy glass windows" and hence the temperature at the plenum goes up, eventually getting to room temp. I turn the system off for a few hours, and then turn it back on to eventually go thru the same situation. My installer states that this is being caused from the extended "heating" season that we have had here and then the quick high temperatures we are experiencing. He states that my "pit" is super cold at this time this is causing the issue. My concern is that this is Michigan and the temperature swings are not out of the ordinary. Has anyone experienced something similar and can someone reccomend a fix for this?

First thing I would check is the air filter.
If your unit is icing due to inadequate heat in the ground, I would have some design questions.
j

Wait, let's get a couple things straight...

It's icing at the ACC (the tank thing with 3 sight glasses on it), not icing at the air coil, right?

The Liquid Flow Control rail (LFC) has a bypass valve, called the Cooling Assist Valve. it may just need to be adjusted so that the pressures are higher when coming out of the heating mode...

Where in MI are you and how old is the unit?
j

Actually, after further investigation, is is icing at the air coil. I have cleaned the air coil and replaced the air filter.

Glad you got it fixed.
I have a Southlyon ph# if you ever need help.
J