Heater System: Other Chevrolet Pickup C2500

TEMPERATURE CONTROL LEVER

The temperature control lever controls discharge air temperature in all mode positions. Full hot position provides maximum heat. Full cold position provides unheated air.

MODE SELECTOR LEVER

The mode selector directs discharge air to windshield, floor, or dash outputs, as desired by driver.

BLOWER SPEED SWITCH

The blower speed knob selects low, medium, or high blower speed.

AUXILIARY HEATER BLOWER SWITCH

A 3-speed blower switch (if equipped) is located on instrument panel, to right of steering column. When switch is in OFF position, auxiliary system does not operate.

CONTROL CABLES

Note. Information on temperature control cable adjustment for Blazer, Pickup, Sierra, Suburban & Yukon series is not available from manufacturer.

BLOWER MOTOR INOPERATIVE

1. Disconnect Orange wire at blower motor. Connect test light between Orange wire at blower motor connector and ground. If test light glows, go to next step. If test light does not glow, check for open Orange wire between blower motor connector and blower resistor connector or between blower resistor connector and blower switch connector. If Orange wire is okay, go to step 3).
2. Connect test light between Orange wire and Black wire at blower motor connector. If test light glows, replace blower motor. If test light does not glow, repair open Black wire between blower motor connector and instrument panel ground connector.
3. Connect test light between Brown wire at blower switch and ground. If test light glows, go to step 4). If test light does not glow, repair open Brown wire between blower switch connector and fuse block. See WIRING DIAGRAMS.
4. Set blower switch to low, medium, or high speed position. Connect test light between ground and blower switch wire associated with position of switch. Low speed position is Yellow wire, medium speed position is Light Blue wire, and high speed position is Orange wire. If test light does not glow, replace blower switch. If test light glows, repair open wire(s) between blower switch and blower resistor.

AUXILIARY BLOWER MOTOR INOPERATIVE

1. Turn ignition on. Set blower switch to high speed position. Connect test light between White wire terminal of blower motor connector and ground. Blower motor connector is located on lower left side of instrument panel. If test light does not glow, go to next step. If test light glows, go to step 3).
2. Repair open White wire between blower motor and blower resistor (located under instrument panel on heater housing), or between blower resistor and high blower relay (located on auxiliary heater). If wire is okay, go to step 4).
3. Connect test light between White wire and Black wire at blower motor. If test light glows, replace blower motor. If test light does not glow, repair open Black wire between blower motor and ground. See WIRING DIAGRAMS.
4. Connect test light between Brown wire at high blower relay and ground. If test light glows, go to next step. If test light does not glow, repair open Brown wire between high blower relay and fuse block.
5. Connect test light between Orange wire and Brown wire at high blower relay. If test light glows, go to next step. If test light does not glow, check for open Orange wire between high blower relay and blower switch. If wire is okay, go to step 7).
6. Check for continuity between Black wire at blower switch and ground. If continuity exists, replace blower switch. If continuity does not exist, repair open Black wire between blower switch and instrument panel ground.
7. Connect test light between Red wire at blower relay and ground. If test light glows, replace blower relay. If test light does not glow, repair open Red wire between high blower relay and battery junction block (located on right rear side of engine compartment).

BLOWER MOTOR OPERATES AT LOW &/OR MEDIUM SPEED ONLY

1. Turn ignition on. Set blower switch to high position. Connect test light between Orange wire at blower switch and ground. If test light glows, go to next step. If test light does not glow, replace blower switch.
2. Connect test light between Orange wire at blower resistor and ground. If test light glows, repair bad connection at Orange wire at blower resistor. If test light does not glow, repair open Orange wire between blower resistor and blower switch.

AUXILIARY BLOWER MOTOR OPERATES AT LOW &/OR MEDIUM SPEED ONLY

1. Turn ignition on. Set blower switch to high speed position. Connect test light between Brown wire at high blower relay (located on auxiliary heater) and ground. If test light glows, go to next step. If test light does not glow, repair open Brown wire between high blower relay and splice near relay leads.
2. Connect test light between Orange wire and Brown wire at high blower relay. If test light glows, go to next step. If test light does not glow, check for open Orange wire between high blower relay and blower switch. If wire is okay, replace blower switch.
3. Connect test light between Red wire at high blower relay and ground. If test light glows, go to next step. If test light does not glow, repair open Red wire between high blower relay and splice near relay leads.
4. Connect test light between White wire at high blower relay and ground. If test light does not glow, replace high blower relay. If test light glows, repair open White wire between high blower relay and blower resistor.

BLOWER MOTOR OPERATES AT HIGH SPEED ONLY

1. Turn ignition on. Set blower switch to speed that does not operate. Connect test light between wire of inoperative speed position at blower switch and ground. Low speed is Yellow wire; medium speed is Light Blue wire.
2. If test light does not glow, replace blower switch. If test light glows, connect test light between Yellow wire or Light Blue wire (depending on switch position) at blower resistor and ground.
3. If test light does not glow, repair open Yellow wire or Light Blue wire between blower resistor and blower switch. Go to next step if test light glows.
4. Connect test light between Orange wire at blower resistor and ground. If test light glows, circuit is okay. If test light does not glow, replace blower resistor.

AUXILIARY BLOWER MOTOR OPERATES AT HIGH SPEED ONLY

1. Turn ignition on. Set blower switch to low speed or medium speed position. Connect self-powered test light between Yellow wire terminal (low speed) or Light Blue wire terminal (medium speed) and ground. If test light glows, go to next step. If test light does not glow, replace blower switch.
2. Connect test light between Brown wire of low or medium blower relay and ground. If test light glows, go to next step. If test light does not glow, repair open Brown wire between low or medium blower relay and splice near relay leads. See WIRING DIAGRAMS.
3. Connect test light between Brown wire terminal of low or medium blower relay and Yellow wire (low speed) or Light Blue wire (medium speed) of blower relay. Set blower switch to inoperative speed. If test light glows, go to next step. If test light does not glow, repair open Yellow or Light Blue wire between blower relay and blower switch.
4. Connect test light between Red wire terminal of low or medium blower relay and ground. If test light glows, go to next step. If test light does not glow, repair open Red wire between blower relay and splice near relay leads.
5. Set blower switch to inoperative speed. Connect test light between Yellow wire or Light Blue wire terminal of blower relay and ground. If test light glows, go to next step. If test light does not glow, replace blower relay.
6. Connect test light between Yellow wire or Light Blue wire terminal of blower resistor and ground. If test light glows, replace blower resistor. If test light does not glow, repair open Yellow wire or Light Blue wire between resistor and low or medium blower relay.

REAR TEMPERATURE DOOR INOPERATIVE

1. Turn ignition on. Set blower switch to low, medium, or high speed position. Connect test light between Brown wire terminal of temperature door relay (located on heater) and ground. If test light glows, go to next step. If test light does not glow, repair open Brown wire between temperature door relay and fuse block.
2. Connect self-powered test light between Black wire terminal of blower switch and ground. If test light glows, go to next step. If test light does not glow, repair open Black wire between blower switch and instrument panel ground connection. See WIRING DIAGRAMS.
3. Connect test light between Brown wire and Dark Green wire of temperature door relay. If test light glows, go to next step. If test light does not glow, check for open Dark Green wire between temperature door relay and blower switch. If wire is okay, replace blower switch.
4. Connect test light between Brown wire and Black wire at temperature door relay. If test light does not glow, repair open Black wire between temperature door relay and ground. If test light glows, connect test light between Brown wire at temperature door relay and ground. If test light glows, go to next step. If test light does not glow, replace relay.
5. Connect test light between Brown wire at temperature door motor and ground. If test light glows, go to next step. If test light does not glow, repair open Brown wire between temperature door motor and temperature door motor relay.
6. Connect test light between Brown wire and Yellow wire at temperature door motor. If test light glows, replace temperature door motor. If test light does not glow, repair open Yellow wire between temperature door motor and temperature door relay.

Scheme 3

Scheme 4

HEATER CORE