The Refrigeration System

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

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

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

Molecular Structure

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

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

Temperature-Pressure Relationship Chart Temp R134A Temp R134A Temp R134a 0 6.5 55 51.2 110 146.3 5 9.1 60 57.4 115 158.4 10 12 65 64 120 171.1 15 15.1 70 71.1 125 184.5 20 18.4 75 78.6 130 198.7 25 22.1 80 86.7 135 213.5 30 25.3 85 95 140 229.2 35 30.4 90 104.3 145 245.6 40 35 95 113.9 150 262.8 45 40 100 124.1 50 45.4 105 134.9

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

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

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

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

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

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

Pressures - high side Reflects condenser temp All systems vary based on ambient temps R12 will typically run 150-250 psi R134a systems up to 300 psi

TXV System

Orifice Tube System

NORMAL OPERATION #1 Low-side gauge: Normal pressure CFC-12 32-33 psig HFC-134a 30-31 psig High Side Gauge: Normal Pressure CFC-12 185-190 psig HFC-134a 204-210 psig

INSUFFICIENT COOLING #2 Low side Gauge: Low Pressure CFC-12 15 psig HFC-134a 12 psig High Side Gauge: Normal Pressure CFC-12 190 psig HFC-134a 208 psig Possible Causes: Thermostat (icing) Low side restriction Moisture in system

INSUFFICIENT OR NO COOLING #3 Low Side Gauge: Low or Very low Pressure CFC-12: 18 psig HFC-134a : 15 psig High Side Gauge: Low Pressure CFC-12: 130-135 psig HFC-134a: 139-144 psig Possible causes: Clogged TXV inlet screen, bad valve, Moisture in system

INSUFFICIENT OR NO COOLING #4 Low side gauge: Low Pressure CFC-12: 22 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

INSUFFICIENT OR NO COOLING #5 Low side: High Pressure CFC-12: 44 psig HFC-134a: 43 psig High side: Low Pressure CFC-12: 140 psig HFC-134a: 150 psig Causes: Bad Clutch, Bad compressor (compressor not turning normally mech... or electrical)

INSUFFICIENT COOLING #6 Low Side: High Pressure CFC-12: 40 psig HFC-1334a 38 psig High Side: Normal Pressure CFC-12: 170 psig HFC-134a: 184 psig Causes: Expansion Valve stuck open

INSUFFICIENT OR NO COOLING #7 Low Side: High Pressure CFC-12: 42 psig HFC-134a: 37 psig High Side: High to extremely High CFC-12: 235 psig HFC-134a: 263 psig Causes: Air in system, Overcharge, overcharge of oil, Clogged condenser, Non op Fans, Engine overheating, Incorrect or contaminated refrigerant