You are losing vacuum from cracked/bad vacuum lines or the vacuum check valve for the HVAC controls is bad. When the engine is under load climbing that hill it does not produce enough vacuum to operate a leaky HVAC system.
Replace the outside temp sensor first.If the car thinks it -32 outside,then the air will not work.
On a 2010 Ford Fusion, the claimant control can stop the air-conditioning blower from blowing air.
Is it blowing cold air only or not blowing any air at all.
smelled electrical burn now central air is blowing warm air non stop
you have a vacuum leak
You may need to recharge your a/c compressor with coolant.
this is most likely a relay under the hood.
a precipitate (aqueous -> solid) must be forming
We can use astoterf on hill to slow the marble
it might be the air condition gas or most probably the air condition compressor
If it stops blowing cold air then your clutch on the compressor is probably not any good, or it could be that you need to recharge your freon and lubricant
sounds like your freon may be low