Why would my Devair DRD50 air dryer not let the air go through it?

by choked
(Calgary,Alberta)

My air dryer in our shop will not let the air flow through later in the day , mainly in the summer. We have replaced the seperator element/ filter in the moisture separator 2 weeks ago and the problem still exists.
After we shut it down, drain ,take it all apart, then put it all together again it will work.
It is on the border of the red on the dewpoint indicator but not completely in the red.
What is the problem and how do I fix it?

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Bill says....

My guess is that you are freezing it up by running it at the maximum for too long. The dryer may be undersized or just at the edge of being undersized, and hot, humid weather would overload it.

Cheers,

Bill