Chapter 4 Air-Conditioning Components

Standard and Optional Equipment

Compressors Usually belt driven from the engine Usually have an electromagnetic clutch to turn on/off Two refrigerant lines suction (larger) draws low pressure, low temp vapor from evaporator discharge (smaller) lets out high pressure, high temp vapor to the condenser

Compressor main functions Raise the pressure of the refrigerant When compressed the refrigerant temperature rises (no heat is added by the compressor) Important for proper heat transfer Create low pressure in the evaporator Allows refrigerant to vaporize (boil) absorbing large amounts of heat Circulate refrigerant and oil

Heat of Compression

Two Piston Compressor (Requires 14 hp to run) York

Intake stroke draws vapor past the intake reed valve

Compression stroke forces intake closed and pushes out compressed vapor through exhaust

Swash Plate Compressor (Requires 7hp to run) Sanden

As the swash plate is rotated, pistons move in and out

Compressor Maintenance Oil level needs to be checked when the system is discharged Compressor seal replacement Replace valve plates or gaskets (low psi) Replace electromagnetic clutch Belt tension

Rotary Vane Compressor Ford used this compressor at one time.

Centrifugal Force throws vanes outward sealing them against the wall

Variable Displacement Compressor Compressor runs continually, no clutch cycling. A control valve senses evaporator load and automatically changes the displacement to meet the system needs.

Maximum displacement, wobble plate maximum angle (compressor runs continuously)

Minimum displacement, wobble plate minimum angle (compressor runs continuously)

Control valve for Variable Displacement The angle of the swash plate is controlled by the bellows activated control valve, located in the rear of the head, that senses the suction pressure.

Scotch Yoke (R4) opposed pistons Used in GM, notorious for shaft seal failures, and being very noisy.

(Scotch Yoke) Pistons pump by following the contour Suction valve in the piston.

Scroll Compressor (requires very little hp found only on small cars) Not very common yet, very efficient.

Inner scroll draws and compresses during rotation

Operation of the Scroll

Oil Loss External leak System recovered in a recovery machine Refrigerant caries out oil System recovered in a recovery machine Measure and reinstall Component replacement Oil can be trapped in the old component Hybrid uses dielectric oil

Check oil in a new compressor

Condenser

Key points Heat moves to less warm Heat transfer quickly with large differences Fins increase surface area to dissipate heat Cooling effect causes refrigerant to change states from high psi vapor to high psi subcooled liquid Must keep clean and fins straight for proper air flow

Fin Comb

Receiver-Drier Liquid refrigerant from the condenser enters Filters Removes moisture Stores excess Pickup tube ensures that only liquid exits (properly charged system) Desiccant is hygroscopic (absorbs moisture) Different for R-12 and 134a Moisture reacts with refrigerant to form hydrochloric acid.

Receiver-Drier Components

Drier Location and Mounting Located in a cool dry place Desiccant can absorb more moisture when it is less warm Mounted vertically Pickup tube in the bottom to only take liquid Mounted horizontally JD uses a side pick-up tube Make sure “top”

Sight Glass R-12 A-normal, B-bubbles, C-oil streaking Bubbles usually indicate a loss of refrigerant, streaking usually indicates no refrigerant.

Moisture Indicator

Warning with Weights