Heating and Air Conditioning: Testing and Inspection

WARNING: Wear eye protection when inspecting the system. Refrigerant at normal atmospheric pressures can evaporate and freeze anything it contacts.

Periodic inspections will help keep the A/C operating at its peak. There are almost always small leaks in the system which will require that it eventually be recharged.

Preliminary Check
- The V-belt which drives the compressor is subject to wear, check condition.
- The condenser fins can become bent or covered with debris, reducing air flow and raising system pressure to damaging levels. With the engine off, clean any debris or bugs from the front of the condenser, and straighten any bent fins using a fin comb.
- Remove the air plenum drip tray and check the fresh air intake for obstructions.
- Inspect the compressor, the hoses, and all visible components for any oil leaks, which are often seen at the bottom side of the fittings and components.
- Inspect the wiring to the pressure switches and compressor clutch.
- Check the compressor mountings for tightness, and check the condition and tension of the V-belt.
- Inspect the refrigerant charge of R-12 by starting the engine and turning the air conditioner on to MAX A/C. With the compressor running, (clutch cycled on) view the sight glass (located in-line near the condenser in the engine compartment). There should be few or no bubbles visible in the glass. A constant foaming indicates that the system charge is low. Streaks on the interior of the glass may indicate that the system is totally discharged.

NOTE: If using an aftermarket product to recharge the system, follow the manufacturer's directions closely. To prevent component damage, a totally discharged system must be evacuated (sometimes called pulling a vacuum), using special equipment, to remove any moisture before recharging.

Performance Test
- Open all instrument panel vents and place a thermometer into the left center vent.
- Run the engine until warm, then set the idle at 2000 rpm with the parking brake firmly set.
- Move the upper control lever to MAX A/C and the temperature control to cold.




- Close the windows and doors. After the A/C compressor has cycled off for the first time, record the temperature. It should be within the range given in the graph.
- If the temperature is not within range, make sure that the air flow is coming only from the center vents and that the recirculation door is closed.
- A temperature difference less than the specified value indicates a problem with the system. Inspect the system as described earlier. Pressure, Vacuum and Temperature Specifications Heating and Air Conditioning/Specifications