Noise Diagnosis. GMC Truck GMC Suburban

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Noise Diagnosis

Noise Description

Source

Solution Recommendation Check

Moan (occurs at a specific RPM, less than other speeds)

Compressor

•	Groundouts

•	Loose Brackets Bolts

•	Exhaust System Ground

•	Low Belt Tension

•	Comp. Torq. cushion (TATC) on HT6 Only

•	Softer Hose Material

Growl (Idle)

Compressor

Groundouts On All A/C Lines and Components

Growl (All Speeds)

Compressor

All Line Clamps and Anchor Points (Remove and Check)

Chatter (Idle)

Compressor

System Refrig. Charge and Oil (Add 1/2# R134A and 3 oz. PAG Oil, Check Effect

Whine (All Speeds) or Grind

Compressor
P/S Pump
Generator

•	Pulley Brg. with A/C On and Off

•	Interference at All Rotating Points of Pulley (Check with Belt On and Off)

Squeal (All Speeds)

Compressor
P/S Pump
Generator

•	Belt Alignment

•	Tensioner Torque

•	Belt Condition (Edge Wear for Rubbing)

Hiss, Gurgle or Percolation

Orifice Tube
TXV (Thermal Expansion Valve)

Occurs at A/C Shut Down (Normal Condition, Noise Subsides After Short Time Period)

Chirp or Thump

Compressor Clutch

Occurs When A/C Cycles on (compressor Clutch Engages or Disengages) - Apply Anti-Seize Compound to Clutch Face (Very Light Coat of Moly Kote or Permatex 2000)

Knock

Compressor

•	Loose Bracket Bolts

•	Belt Tensioner

Blower Noise

A constant air rush noise is typical of high speed blower operation. Some systems and modes are more noisy than other systems. If possible, verify the noise using a similar vehicle in order to determine if the noise is typical or excessive.

Vibration/Rattle

Important: Feel the lines, the hoses, and the brackets during the diagnosis. Many noises stop when you contact the component.

Potential causes include the following conditions:

•	The belt is not in proper alignment in the pulley groove.

•	The belt tensioner is faulty.

•	The lines or the hoses are in contact with each other.

•	The brackets are loose.

•	Other drive components are faulty.

Moans

Potential causes include the following conditions:

•	The A/C charge is not proper.

•	Other drive components are faulty.

•	A bracket is loose or is not in proper alignment.

•	The lines or the hoses are in contact with each other.

•	The heater hoses are not correctly routed.

Screech

Potential causes include the following conditions:

•	The belt is serpentine.

•	The compressor bearings are faulty.

•	The compressor clutch is faulty.