Heating System - GMC 1994 Yukon Owner's Manual

Heater Output
Engine Coolant Heater
If your vehicle has a diesel engine, it is equipped with an engine coolant
heater. An engine coolant heater is optional on gas engine vehicles. You can
use an engine coolant heater during initial start-up in cold weather (20" F,
-8"
C, or lower) to help heat the passenger compartment faster. Because an
engine coolant heater warms the engine coolant, your vehicle's heating
system can provide some heat as soon as you start the engine.
The use of an engine coolant heater also reduces the time it takes for the
engine to reach normal operating temperature, and shortens the time it takes
the heater to reach full output. For more information, See "Engine Coolant
Heater" in the Index.
Diesel Engine
If you idle your diesel engine for a long time when it's cold outside, your
heater may blow out cool air. This is normal. When you increase the engine
speed, your heater should blow out warmer air. If it doesn't, your coolant
level may be low. See "Engine Coolant" in the Index to find out how to
check your coolant level.
Heating System (Without Air Conditioning)
If your vehicle does not have air conditioning, this is what your heating
system will look like.
3-4