GMC 1986 P-Truck Service Manual page 60

200. Seal
201. Outlet
202. Valve Assembly
GENERAL DESCRIPTION
An auxiliary heater provides additional heating for
the rear area on some models.
It operates independently of the standard heater, and
is regulated through its own control at the instrument
panel.
This system consists of a separate core fan vent.
Heater hoses extend from the unit to the front of the
vehicle where they are connected to the standard
heater hoses with " tees" (figure 21).
DIAGNOSIS
Refer to " C-K and G Series Heaters.'
WATER VALVE
An " on-off" vacuum-operated water valve, installed
in the heater core inlet in the engine compartment,
controls coolant flow to the auxiliary core and
eliminates radiant heat during warm weather.
203. Clip
204. Screw
205. Knob
Figure 19—Vents
G SERIES AUXILIARY HEATER
206. Rod
209. Seal
207. Guide
210. Inlet Assembly
208. Outlet
211. Cover
FAN SWITCH
For heating, the fan switch is placed in any position
except off. The switch opens the water valve which
permits hot water to enter the heater core. In the OFF
position, the valve is closed to prevent unwanted heat
during warm weather.
ON-VEHICLE SERVICE
RESISTOR REPLACEMENT
Remove or Disconnect (Figure 18)
1. Battery ground cable.
2. Wiring harness at the resistor connector.
3. Resistor mounting screws.
4. Resistor.
Install or Connect (Figure 18)
♦ « -
1. Resistor.
2. Mounting screws.
3. Wiring harness.
4. Battery ground cable.
HEATING 1A-21
F-00657