Chevrolet Silverado / GMC Sierra. Service manual — part 1218

HEATER SYSTEM TROUBLE SHOOTING

BASIC HEATER SYSTEM TROUBLE SHOOTING CHART

. .

Blocked evaporator fins.

. .

Vacuum system leak.

. .

Vacuum motors inoperative.

. .

Control cables improperly adjusted.

. .

Restricted air inlet.

. .

Mode doors binding.

. .

Blower motor inoperative.

. .

Temperature above system capacity.

NOTE:

This is GENERAL information. This article is not intended to be
specific to any unique situation or individual vehicle configuration.
The purpose of this Trouble Shooting information is to provide a list
of common causes to problem symptoms. For model-specific
Trouble Shooting, refer to DIAGNOSTIC, or TESTING articles
available in the section(s) you are accessing.

CONDITION

POSSIBLE CAUSE

Insufficient, Erratic, or No Heat

Low Coolant Level

. .

Incorrect thermostat.

. .

Restricted coolant flow through core.

. .

Heater hoses plugged.

. .

Misadjusted control cable.

. .

Sticking heater control valve.

. .

Vacuum hose leaking.

. .

Vacuum hose blocked.

. .

Vacuum motors inoperative.

. .

Blocked air inlet.

. .

Inoperative heater blower motor.

. .

Oil residue on heater core fins.

. .

Dirt on heater core fins.

Too Much Heat

Improperly adjusted cables.

. .

Sticking heater control valve.

. .

No vacuum to heater control valve.

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

BRAKES

BRAKE SYSTEM TROUBLE SHOOTING

BRAKE SYSTEM TROUBLE SHOOTING CHART

. .

Temperature door stuck open.

Air Flow Changes During
Acceleration

Vacuum system leak.

. .

Bad check valve or reservoir.

Air From Defroster At All Times

Vacuum system leak.

. .

Improperly adjusted control cables.

. .

Inoperative vacuum motor.

Blower Does Not Operate
Correctly

Blown fuse.

. .

Blower motor windings open.

. .

Resistors burned out.

. .

Motor ground connection loose.

. .

Wiring harness connections loose.

. .

Blower motor switch inoperative.

. .

Blower relay inoperative.

. .

Fan binding or foreign object in housing.

. .

Fan blades broken or bent.

NOTE:

This is GENERAL information. This article is not intended to be
specific to any unique situation or individual vehicle configuration.
The purpose of this Trouble Shooting information is to provide a list
of common causes to problem symptoms. For model-specific
Trouble Shooting, refer to SUBJECT, DIAGNOSTIC, or TESTING
articles available in the section(s) you are accessing.

CONDITION & POSSIBLE CAUSE

CORRECTION

Brakes Pull Left or Right

Incorrect tire pressure

Inflate tires to proper

pressure

Front end out of alignment

See WHEEL

ALIGNMENT

Mismatched tires

Check tires sizes

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Restricted brake lines or hoses

Check hose routing

Loose or malfunctioning caliper

See DISC BRAKES or

BRAKE SYSTEM

Bent shoe or oily linings

See DRUM BRAKES or

BRAKE SYSTEM

Malfunctioning rear brakes

See DRUM, DISC

BRAKES or BRAKE

SYSTEM

Loose suspension parts

See SUSPENSION

Noises Without Brakes Applied

Front linings worn out

Replace linings

Dust or oil on drums or rotors

See DRUM, DISC

BRAKES or BRAKE

SYSTEM

Noises With Brakes Applied

Insulator on outboard shoe damaged

See DISC BRAKES or

BRAKE SYSTEM

Incorrect pads or linings

Replace pads or linings

Brake Rough, Chatters or Pulsates

Excessive lateral runout

Check rotor runout

Parallelism not to specifications

Reface or replace rotor

Wheel bearings not adjusted

See SUSPENSION

Rear drums out-of-round

Reface or replace drums

Disc pad reversed, steel against rotor

Remove and reinstall pad

Excessive Pedal Effort

Malfunctioning power unit

See POWER BRAKES or

BRAKE SYSTEM

Partial system failure

Check fluid and pipes

Worn disc pad or lining

Replace pad or lining

Caliper piston stuck or sluggish

See DISC BRAKES or

BRAKE SYSTEM

Master cylinder piston stuck

See MASTER

CYLINDERS or BRAKE

SYSTEM

Brake fade due to incorrect pads for linings

Replace pads or linings

Linings or pads glazed

Replace pads or linings

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Worn drums

Reface or replace drums

Excessive Pedal Travel

Partial brake system failure

Check fluid and pipes

Insufficient fluid in master cylinder

See MASTER

CYLINDERS or BRAKE

SYSTEM

Air trapped in system

See BRAKE BLEEDING

or BRAKE SYSTEM

Rear brakes not adjusted

See Adjustments in

DRUM BRAKES or

BRAKE SYSTEM

Bent shoe or lining

See DRUM BRAKES or

BRAKE SYSTEM

Plugged master cylinder cap

See MASTER

CYLINDERS or BRAKE

SYSTEM

Improper brake fluid

Replace brake fluid

Pedal Travel Decreasing

Compensating port plugged

See MASTER

CYLINDERS or BRAKE

SYSTEM

Swollen cup in master cylinder

See MASTER

CYLINDERS or BRAKE

SYSTEM

Master cylinder piston not returning

See MASTER

CYLINDERS or BRAKE

SYSTEM

Weak shoe retracting springs

See DRUM BRAKES

BRAKE SYSTEM

Wheel cylinder piston sticking

See DRUM BRAKES or

BRAKE SYSTEM

Dragging Brakes

Master cylinder pistons not returning

See MASTER

CYLINDERS BRAKE

SYSTEM

Restricted brake lines or hoses

Check line routing

Incorrect parking brake adjustment

See DRUM BRAKES

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures