Charging the System

Before attempting to charge the system, read the discussion in Chapter 1 on air-conditioning. Familiarize yourself with all the components of the system so you will understand how to check and charge it, and add refrigerant to it.

Locating the sight glass

The quickest way to determine if your air-conditioning system is low on refrig-erant is to check the system through the sight glass usually located on the outlet side of the receiver-drier. Some sight glasses have a protective cover made of cardboard or stiff paper. Remove the cover if there is one on your system. On some cars, the sight glass is not mounted on the receiver-drier, but on the line between the condenser and the expansion valve.

Bypassing a damaged heater core

Your heater core may be dam-aged if you notice fogginess, dampness, or actual leakage of engine coolant into the passenger compartment. These signs are most noticeable when the heater is on. A quick-fix so you can use the car while the heater core is being repaired is to place a six-inch piece of %-inch-diameter tubing into both heater hoses after disconnecting them from the heater core at the firewall. This will bypass the heater system entirely.

Using the sight glass

1 Checking the clutch. Start the en-gine with the parking brake applied and the transmission in "Park." Set the air-conditioning controls to maximum cooling and high fan levels. Open the hood, and make sure the entire compressor
clutch assembly is being turned by the air-conditioning belt. Have a helper switch the air-conditioner control off and on while you observe the clutch assembly engaging and disengaging. If the clutch is not engaging, you cannot check the system at this time. Troubleshooting this problem will be covered later in this chapter.

2 Looking into the sight glass, noth-ing should be visible;it should appear empty. If it does, and cold air is circu-lating in the passenger compartment, the system is sufficiently charged. If the sight glass is clear but there is no cold air circulating in the passenger compart ment, the system may be empty. Take your car to an auto mechanic or air-conditioning specialist for further checking and servicing. If the sight glass shows bubbles that look like moving water bubbles, the system needs to be charged with refrigerant.

Adding refrigerant

1 Removing the low-side Schrader valve. Place fender covers over the front fenders. Wearing eye goggles for protection, locate the low-side charging Schrader valve. It looks like a tire valve with its cover removed, and is usually lo-cated in the line between the evaporator and the compressor directly on the com-pressor, or on the suction throttle valve. Remove the valve's acorn cap cover. Caution: There is a second Schrader valve located in the line between the compressor and the condenser. This is the high-pressure charging valve, and you should not work on it. It should only be serviced by a mechanic using a manifold hand set.

2 Install the refrigerant can tap and hose on the can according to the in-structions accompanying the tap and hose kit. Connect the hose to the low-side Schrader valve finger tight, then loosen the hose connection at the can tap slowly until a small amount of refrigerant escapes from the connection. This will purge the hose, removing all air and moisture from it. Then tighten the connection finger tight again. Open the valve on the can tap. At this point the refrigerant should start to flow into the system.

3 Have your helper operate the en-gine at a fast idle while you place the R-12 can upright in a pail of hot water. The water will raise the temperature of the refrigerant, increasing the pressure and permitting it to flow into the system easily. Caution: Do not invert the refrig-erant can. If you do, liquid refrigerant, in-stead of a gas refrigerant, will enter the system and damage the compressor.

4 While the system is charging, watch the sight glass. Continue charging until the bubbles vanish and the sight glass is clear, then turn off the can tap valve. Have your helper run the engine at normal idling speed. Allow the engine and the system to operate for a few minutes to stabilize it, then recheck the sight glass. With the engine still idling, place a hand cloth around the hose connection at the Schrader valve and very quickly remove the hose fitting. Replace the acorn nut cover.