Cadillac Repair: Northstar overheating, blown head gasket, head gasket problem

Question
I have a 2000 deVille with 165000 miles. I recently noticed coolant leaking at night. The mechanic found a small leak...after considering the options, I chose to replace the radiator with a new one. The mechanic also thought that the water pump was not running properly, and GM replace that with a new pump. The car has never run hot before. After the repairs were made, the car ran fine; the passengerheatg/cooling had evidently been turned off while the work was being done. When I switched the A/C on, the car engine quickly heated up and I had to pull over. The warning light said to turn off the A/C. After a month with the car still in the shop, it still overheats when the A/C is on, but runs fine otherwise?

Please give me your opinion, and if this is a blown head gasket problem, can this be repaired, do I need a new engine, or a new car? I like this car a lot and would love to be able to keep it!

Thanks

Answer
Are you POSITIVE that BOTH electric fans are RUNNING when the A/C is turned ON. It is possible that he forgot to attach one of the fan wires OR if the engine temp ran fine BEFORE the coolant pump was installed, It is possible that you have a bad pump ar it may not be installed correctly.