Extralien

Sounds like a built in safety feature to stop overheating of the system.

Usually ( from my own experience) this is due to the cooling raditors becoming clogged with dirt/dust.

It's not too much of a major problem.
irst radiator will be outside the house at the rear of the unit.. hose it down or use a hand held squirter to squirt clean water through the radiator.

Second radiator wil be inside house behind the main front cover. Some filters are not always that effective at stopping all the dust and the radiators get condensation on them so the dust collects and sticks.

disconnect power supply, remove front housing and either use a hand hed squirter and/or a wet brush to clean the radiator.

This might solve the problem and also allow the unit to keep the air cool once again.