Protective Devices

CHAPTER TWENTY ONE

T-34C AIRCRAFT SYSTEMS FAMILIARIZATION

WORKBOOK

The air exiting the evaporator enters the cockpits through air outlets on the front and sides of the

console. A louver assembly on the front of the console enables the pilot to adjust the direction

and volume of the air. Outlets on the side of the console are not adjustable. Temperature in each

cockpit can be maintained through adjustment of the console air outlets, controlling the fan speed

with the AIR rheostat, or turning the toggle switch to OFF.

Protective Devices

Protection for the air conditioning system is provided through two pressure-sensing devices. A

high-pressure (380 PSI) switch located in the engine compartment on the right side of the

firewall senses the pressure of the refrigerant as it leaves the condenser. Should the pressure

reach 380 PSI, a circuit breaker within the switch opens the electrical circuit and interrupts DC

power to the compressor clutch, thereby protecting all system components from overpressure

damage. The low pressure (3 PSI) switch is located in the engine compartment on the right side

of the firewall immediately to the left of the high-pressure switch. This switch is sensitive to the

refrigerant pressure entering the compressor. Should there be a loss of refrigerant (and its

lubricating oil) and the pressure reaches 3 PSI, a fuse is blown, interrupting electrical power to

the clutch and the clutch disengages. The compressor bearings and pistons are protected from

damage due to loss of lubrication. The circuit breaker cannot be reset and the fuse cannot be

replaced in flight.

21-4 AIR CONDITIONING SYSTEM