Safety Precautions for General Air Conditioning System

• Wear gloves when connecting or disconnecting service gauge hoses.

• Always wear eye protection when working around refrigerant and air conditioning systems. Since the system's high side is under high pressure, severe injury to the eyes could result if a hose were to burst. Refrigerant also evaporates rapidly when exposed to the atmosphere, causing it to freeze anything it contact. That's why it's a good idea to protect skin and clothing with a shop coat. And a bad idea to wear loose clothing or things like ties or jewelry that could get caught in the drive belts.

• Never strike a section of copper or aluminum tubing or a heat exchanger in a charged refrigeration system. A blow from a heavy tool could easily cause the relatively soft material to rupture.

• If you have to apply force to a pressurized refrigerant threaded fitting, always use a back-up wrench to avoid the direct transfer of excessive torque to a section of refrigerant tubing. Whenever possible, use wrenches specially designed for "1/4 inch flare nut" fittings (R-12 systems) or for 112-inch "Acme" fittings (R-134a systems).

Identifying The Causes of Overheating

Some overheating problems aren't related to the cooling system at all. Other circumstances that can cause a vehicle to overheat include lack of oil, a blown head gasket, and transmission problems. If the cooling system seems to be in good order after you check it and do the maintenance work in this chapter, investigate these possibilities :

• Late timing : If you haven't tuned and timed your engine recently, late timing may be causing it to overheat by making the spark plugs fire the fuel/air mixture after the piston moves back down from the top of its stroke. When the spark plugs fire too late to allow all the gases to burn properly, more heat burdens your cooling system. Late timing alone doesn't cause a car to overheat by more than a few degrees, but coupled with other problems, it can bring the engine temperature to a critical point. The remedy is simple: Just check your timing and adjust it.