Ge monogram refrigerator help!!

I bought a Ge Monogram refrigerator (42 inch) a while back and just now tried it. It is at least 10 years old and has not run in at least 5 years.
My problem
When I run it, the freezer cools to around zero, then the evaporator coils freeze up,solid, the evaporator and condenser fans both run fine. The condenser low side shows 5 lbs vacuum on the gage when running. It shows around 40 lbs positive when system is off (static).
The timer seems to work OK, the coils heat and melt the ice in the defrost mode. I thought when the condenser is in a vacuum it needs freon. But when the evaporator coils freeze up it has too much freon.
Any thoughts or checks I can do? Could the expansion valve be clogged? Any site that can help?

Have you checked out the defrost timer switch? What you are describing sounds like that switch went bad other wise the coils would not be freezing up. I doubt the system has too much freon.

Twinkiedooter
Thanks for the answer.
I ran a check of the defrost mode. Set the timer to defrost. The defrost mode ran for maybe a half an hour. When it finished the evaporator coils were clean, no frost whatsoever. The compressor started up and the cooling cycle began. I am guessing this is an 8 hour time cycle. Frost began by the end of the first hour. Had maybe a 1/4 inch of frost on the motor, (it was running), and noticeable frost on the evaporator coils. The freezer temp was close to zero after 2 hours give or take. By 3 hours the evaporator coils were completely iced over, no way for air to pass through. Both compressor and evaporator fans ran the entire time.
Any guesses?
There are 2 I am guessing temp switches on the evaporator coil. Is one to turn off the heat when the evaporator coils reach a certain temp during the defrost cycle? If so what is the other temp switch do?
I am scratching my head a bit now...

Ps, The evaporator coil fan brings air in from the freezer up and blows the air through the coil then returns to the freezer.