Hummer H2. Manual — part 24

BASIC AIR CONDITIONING TROUBLE SHOOTING CHART

HEATER SYSTEM TROUBLE SHOOTING

SUBJECT, DIAGNOSTIC, or TESTING articles available in the section(s)
you are accessing.

CONDITION

POSSIBLE CAUSE

Compressor Not Working

Compressor clutch circuit open.

. .

Compressor clutch coil inoperative.

. .

Poor clutch ground connection.

. .

Fan belts loose.

. .

Thermostatic switch inoperative.

. .

Thermostatic switch not adjusted.

. .

Ambient temperature switch open.

. .

Superheat fuse blown.

Excessive Noise or Vibration

Missing or loose mounting bolts.

. .

Bad idler pulley bearings.

. .

Fan belts not tightened correctly.

. .

Compressor clutch contacting body.

. .

Excessive system pressure.

. .

Compressor oil level low.

. .

Damaged clutch bearings.

. .

Damaged reed valves.

. .

Damaged compressor.

Insufficient or No Cooling; Compressor Working

Expansion valve inoperative.

. .

Heater control valve stuck open.

. .

Low system pressure.

. .

Blocked condenser fins.

. .

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

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

BASIC HEATER SYSTEM TROUBLE SHOOTING CHART

BRAKES

BRAKE SYSTEM TROUBLE SHOOTING

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.

. .

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.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

BRAKE SYSTEM TROUBLE SHOOTING CHART

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

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

Replace pads or linings

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

linings

Linings or pads glazed

Replace pads or linings

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 BRAKE SYSTEM

Parking Brake cables frozen

See DRUM BRAKES BRAKE SYSTEM

Incorrect installation of inboard disc
pad

Remove and replace correctly

Power booster output rod too long

See POWER BRAKE UNITS BRAKE

SYSTEM

Brake pedal not returning freely

See DISC, DRUM BRAKES BRAKE SYSTEM

Brakes Grab or Uneven Braking Action

Malfunction of combination valve

See CONTROL VALVE or BRAKE SYSTEM

Malfunction of power brake unit

See POWER BRAKE UNITS or BRAKE

SYSTEM

Binding brake pedal

See DISC, DRUM BRAKES or BRAKE

SYSTEM

Pulsation or Roughness

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures