2004 Hummer H2 Owner's Manual - Page 101

Engine Coolant Heater Your vehicle may be equipped with an engine coolant heater. In very cold weather, 0°F (−18°C) or colder, the engine coolant heater can help. You'll get easier starting and better fuel economy during engine warm-up. Usually, the coolant heater should be plugged in a minimum of four hours prior to starting your vehicle. At temperatures above 32°F (0°C), use of the coolant heater is not required. 3. Plug it into a normal, grounded 110-volt AC outlet. {CAUTION: Plugging the cord into an ungrounded outlet could cause an electrical shock. Also, the wrong kind of extension cord could overheat and cause a fire. You could be seriously injured. Plug the cord into a properly grounded three-prong 110-volt AC outlet. If the cord will not reach, use a heavy-duty three-prong extension cord rated for at least 15 amps. 4. Before starting the engine, be sure to unplug and store the cord as it was before to keep it away from moving engine parts. If you don't, it could be damaged. How long should you keep the coolant heater plugged in? The answer depends on the outside temperature, the kind of oil you have, and some other things. Instead of trying to list everything here, we ask that you contact your dealer in the area where you'll be parking your vehicle. The dealer can give you the best advice for that particular area. To Use the Engine Coolant Heater 1. Turn off the engine. 2. Locate the electrical cord near the front recovery loop on the driver's side of the vehicle. 2-21