1. The Refrigeration System

2. PREPARATION Develop a consistent routine. Use Common Sense Approach
Consult Service Manuals
Cleanliness
Safety

3. CHECK THESE FIRST BELT TENSION COMPRESSOR CLUTCH OP COOLING FAN OP
BLOWER MOTOR OP
AIR FLOW FROM DUCTS
REFRIGERANT CHARGE
SERVICE VALVES
LINES, HOSES, CONNECTIONS
AMBIENT AIR TEMP

4. Refrigerant A compound used in mechanical refrigeration systems
Used to transfer heat
R-134A used since 1996
Contains no chlorine
Many older systems can be converted to R-134A
Available in 1lb & 33lb
Must have certification to purchase

5. Molecular Structure

6. Refrigerant Oil Lubricates compressor & TXV Mineral oil in R12 systems
Polyalkylene Glycol (PAG) oil in R134A systems, blue color (water based)
Must maintain specific amount in system
Never reuse old oil, add fresh oil

7. Temp & Pressure Relationship
To keep Evap just above freezing (icing)
Refrigerant temps & pressures closely related
Low side temp/ Evap
High side temp/condenser

8. Temperature-Pressure Relationship Chart
Temp R134A Temp R134A Temp R134a

9. A/C temperature testing
True test of systems ability to cool
Is normally measured at center outlet
Procedure:
Run med blower, 1500 rpm
Engine warm let idle, blower low
Measure center vent
Should be 20 degrees reduction over incoming air

10. A/C pressure testing MUST WEAR EYE PROTECTION!!!
Manifold gauge set
Low side gauge
A compound gauge reads both pressure & vacuum
low side, blue hose

11. A/C pressure testing High side gauge Measures pressure only
High side, red hose

12. A/C pressure testing Yellow center hose Two hand valves control flow.
Hooked to service equipment
Two hand valves control flow.
Must be closed while testing
All hoses are anti-blowback

13. Test ports Quick connect
Covered by protective caps, reduces slow leakage
Special schrader valve

14. Pressures - low side Reflects evap temp R12 systems run 25-35 psi
R134a systems run 20-25psi

15. Pressures - high side Reflects condenser temp
All systems vary based on ambient temps
R12 will typically run psi
R134a systems up to 300 psi

16. TXV System

17. Orifice Tube System

18. NORMAL OPERATION #1 Low-side gauge: Normal pressure
CFC psig HFC-134a psig
High Side Gauge: Normal Pressure CFC psig HFC-134a psig

19. INSUFFICIENT COOLING #2
Low side Gauge: Low Pressure CFC psig HFC-134a 12 psig
High Side Gauge: Normal Pressure CFC psig HFC-134a psig
Possible Causes: Thermostat (icing) Low side restriction Moisture in system

20. INSUFFICIENT OR NO COOLING #3
Low Side Gauge: Low or Very low Pressure
CFC-12: psig
HFC-134a : 15 psig
High Side Gauge: Low Pressure
CFC-12: psig
HFC-134a: psig
Possible causes: Clogged TXV inlet screen, bad valve, Moisture in system

21. INSUFFICIENT OR NO COOLING #4
Low side gauge: Low Pressure
CFC-12: psig
HFC-134a: 20 psig
High side gauge: High to extremely High
CFC-12: 250 psig
HFC-134a 281 psig
Causes: Restriction in High Side
Temperature change present at restriction

22. INSUFFICIENT OR NO COOLING #5
Low side: High Pressure
CFC-12: psig
HFC-134a: 43 psig
High side: Low Pressure
CFC-12: psig
HFC-134a: 150 psig
Causes: Bad Clutch, Bad compressor
(compressor not turning normally mech... or electrical)

23. INSUFFICIENT COOLING #6
Low Side: High Pressure
CFC-12: 40 psig
HFC-1334a 38 psig
High Side: Normal Pressure
CFC-12: psig
HFC-134a: psig
Causes: Expansion Valve stuck open

24. INSUFFICIENT OR NO COOLING #7
Low Side: High Pressure
CFC-12: psig
HFC-134a: 37 psig
High Side: High to extremely High
CFC-12: psig
HFC-134a: 263 psig
Causes: Air in system, Overcharge, overcharge of oil, Clogged condenser, Non op Fans, Engine overheating, Incorrect or contaminated refrigerant