low refrigerant. stored liquid refrigerant boils away after 2-3 minutes, suction pressure drops, compressor shuts off on low suction pressure.
if its blowing, but not blowing cold its low on coolant. it takes r134a.
think about it they have independent control thus they have separate cooling systems
If it does blow just not cold air you should see if it needs to be recharged
Cause its broke!
Your thermostat is the likely culprit here it is probably stuck closed. Have it checked out.
It doesn't really blow it out it just warms the cold air.
How cold is it. Most diesel engine do not responed properly when the engine and fuel is cold.
you may not have the heater water hoses plugged in
The heater valve could be failing to open for one reason or another.
Low coolant in the system. Defective heater control valve. Clogged heater core.
check your coolant level
How cold does it get where you are? Look at the container the coolant comes in. It will tell.