1. A/C testing and service

2. Before testing and service, technician must be certified by ASE, MACS, or IMACA

3. A/C temperature testing u True test of systems ability to cool u Is normally measured at center outlet u Procedure: –After running system on medium fan and engine at 1500-2000rpm, turning blower on low will slow down air flow over evaporator –This will be coldest reading used for testing –Basic rule of thumb: cooling should be 20 degrees reduction over incoming air

4. A/C temperature testing u More accurately tested with electronic thermometers –Often used in conjunction with DMMs called thermocouples

5. A/C pressure testing MUST WEAR EYE PROTECTION!!! u Manifold pressure gauge set normally consists of two gauges and three hoses u Low side gauge –A compound gauge reads both pressure (usually to 150 psi) and vacuum (usually to 30”hg) –Hooked only to low side through a blue hose

6. A/C pressure testing u High side gauge –A high pressure gauge that reads usually to 500 psi –Hooked only to high side with a red hose –May need high side adapter

7. A/C pressure testing u Center hose is usually yellow –Yellow hose is hooked to service equipment such as a vacuum tank or refrigerant bottle u Two hand valves for controlling flow through gauge set u All hoses must be anti-blowback design by law

8. Test ports and valves u R12 systems will use ¼” flare fittings for the low side ports u R12 systems can use ¼”, 3/16”, 1/8” flare fittings for high side test ports to avoid incorrect hookup

9. Test ports and valves u R134a systems will use a 13mm O.D. quick disconnect connector for low side test ports u R134a systems will use a 16mm O.D. quick disconnect connector for high side test ports

10. Test ports u Test ports will be covered by a protective cap, mandatory to avoid slow leakage u Test ports will contain a special schrader valve designed for operation in refrigerant

11. Service valves at compressor u Used to isolate compressor from rest of system for repairs u Will have three positions - backseated, mid position, frontseated

12. Pressures - low side u Low side pressures should reflect evaporator temperature u R12 systems will run 25-35 psi typically –Variable displacement compressors can run into the 50psi range –Cycling clutch systems will pull down to below 30 psi and then usually cycle off to about 45-55psi before turning on again –R134a systems will run 18-40 psi typically

13. Pressures - high side u High side or head pressures should reflect condenser temperature –All systems vary widely based on ambient temps –R12 will typically run 150-250 psi v System with electric cooling fans will cycle high with fan off then low when the fan turns on –R134a systems will run somewhat higher - up to 300 psi

14. Diagnosis thoughts for complaints / pressure problems

15. Low refrigerant u All pressures will be low u Compressors will cycle often in a CCOT system u LOOK FOR LEAKS

16. Excessive refrigerant u High side high but low side is metered down to normal/near normal pressures u In CCOT, all pressures high because volume is too high

17. Damaged compressor / stuck open TXV u Will not pump refrigerant and cause very little pressure change from high to low side

18. Restrictions u Cause high pressures before and low after u Temperature drops are greatest after restrictions (icy hoses or components) u Commonly plugged orifice tubes

19. Overheating condenser u Will cause high head pressures and high low pressures u Usually inadequate air flow

20. Iced evaporator u Usually reflected in lower than normal low side pressures u Often reduced air flow out ducts

21. A/C leak testing u Electronic leak detectors –Must be used under suspected leak –Most common today u Dyes –Added to A/C like refrigerant –Can be visible to naked eye or fluorescent type u Flame type tool (antique) –Obvious dangers with phosgene gas –Will not work on R134a systems

22. Retrofitting u Changing R12 system over to R134a u Remove most of mineral oil u Flush condensor u Replace dessicant u Manufactures recommend multiple component replacements u Change over all fittings and add labels u Add only portion of R134a with new style oil

23. Servicing AC systems u ON CAR

24. END