2008 2500 HD Diesel Chevy air conditioning clutch wont engage.

. I tested with air on in coldest position. I tested the low line and it was 100 psi. I would
guess this would be considered a static reading since clutch would not engage.  Dealer
says that the 100psi in Low line is more than the can of coolant I was beginning to put
in and that it would try and push back into the can. Said it would be dangerous. I don't
wrench for a living but have done maintenance on my vehicles for years. Anyone care
to chime in on possible next steps? Thx,