Chevrolet 1996 Tahoe Owner's Manual page 76

To use the coolant heater:
1. Turn off the engine.
2. Open the hood and unwrap the electrical cord.
3. Plug it into a normal, grounded 110-volt AC outlet.
4
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 won't reach, use ,a
heavy-duty three-prong extension cord rated for
at least 15 amps.
4. After you've used the coolant heater, be sure to
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 depknds 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 GM dealer in the area where you'll be parking your
vehicle. The dealer can give you the best advice for that
particular area.