AC Problem can’t be found by mechanic

My 2010 Mustang GT has had new blendor, radiator fan, compressor + kit installed. AC runs great for 20 mins then no more cold. Mechanic says compressor not kicking in. Please don’t say Freon or faulty parts. All checked and rechecked. Mechanics are stumped. What could it be???? PLEASE HELP!!!
 
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Without knowing the history of how you got to this point...A couple,of things to look at or think about:
--is the evaporator icing up when the compressor runs? (You should see ice forming on the evaporator lines)...if so, suspect a bad temperature sensor
--if your old compressor gutted itself and blew metal shards into the system (which may not have been flushed well)...suspect clogged orifices in the expansion valve (and get everything properly flushed before you damage the new compressor)
--recheck and jump/bypass each of the high/low/cycling switches to see if the compressor clutch will engage...further, check or replace the AC compressor relay with a known good part
--double check exposed AC wiring for breaks or shorts to ground
--put the gauges on it and doublecheck the Freon charge
Good luck.
 
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Without knowing the history of how you got to this point...A couple,of things to look at or think about:
--is the evaporator icing up when the compressor runs? (You should see ice forming on the evaporator lines)...if so, suspect a bad temperature sensor
--if your old compressor gutted itself and blew metal shards into the system (which may not have been flushed well)...suspect clogged orifices in the expansion valve (and get everything properly flushed before you damage the new compressor)
--recheck and jump/bypass each of the high/low/cycling switches to see if the compressor clutch will engage...further, check or replace the AC compressor relay with a known good part
--double check exposed AC wiring for breaks or shorts to ground
--put the gauges on it and doublecheck the Freon charge
Good luck.


Unfortunately the whole damn system was replaced. Problem still exists
 
Did you ever find out what was the problem ? I have the same issue with my 2006 GT. AC ias got for first 15-20 min then works only for like 1-2 minutes every 10 minutes after that.. Have replaced the fuse, relay and ac compressor with clutch. Clutch will work normally when bypass the relay.