Heating/air Conditioning: NVH Honda Pilot II

A/C System Noise Check

The A/C system noise check will help you determine the source of abnormal A/C system noise.

Note. If accidental system discharge occurs, ventilate the work area before resuming service. Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers. Identify the confitions when the noise occurs. The weather, the vehicle speed, the vehicle being in gear or in neutral, the engine temperature or other confitions may be factors in determining the noise source. Do an A/C system inspection (see A/C System Inspection ) and correct any problems fround prior to diagnosing abnormal noises. Abnormal A/C noises can be misleading. For example, a sound similiar to a failed bearing may be caused by loose fasterners, loose mounting brackets or a faulty compressor clutch assembly.

1. Inspect the air inlet grille in the cowl cover for debris. If debris is present, remove it.
2. Sit inside the vehicle, close the doors and windows and turn the ignition switch to ON (II), but do not start the engine. Cycle the HVAC system through all blower speeds and all air distribution modes to determine where and when the noise occurs.
3. Operate the blower at each speed with the engine and A/C off and check for unusual noises and excessive vibration. If noise and/or vibration are present, do the following checks: If the noise or vibration occurs only in a specific mode or setting, then check these items: Operation of the mode control motor, door and linkage Operation of the air mix control motors, doors and linkage Operation of the recirculation motors, doors and linkage If there is a squeaking or chirping noise, but no unusual vibration, replace the blower motor (see «Blower Unit Component Replacement»(ref-333580-S20644170882009072100000) ). Remove the blower unit (see «Blower Unit Removal/Installation»(ref-333580-S00246683242009072100000) ) and check for foreign material (leaves or twigs, for example) on the blower motor and fan. If foreign material is present, remove it and recheck for noise. If you don't find any foreign material, remove the blower motor (see «Blower Unit Component Replacement»(ref-333580-S20644170882009072100000) ) and check these items: Check if the fan blades are cracked or broken Make sure the fan retainer is tight Inspect the fan alignment on the blower motor shaft Replace the blower motor if any problems are present.
4. Set up the vehicle for the running A/C checks: Select a quiet area for testing Apply the parking brake Shift the vehicle in PARK or in Neutral Start the engine Set the temperature control button to Max Cool Set the mode control button to Vent Set the fan ON/OFF button to minimum (but not OFF) Turn the A/C button ON Switch the compressor on and off several times to clearly identify the sound during A/C compressor operation. Listen to the noise while the A/C compressor clutch is engaged and disengaged. Probe the A/C system with a stethoscope to pinpoint the noise. NOTE: If the noise does not change when the A/C compressor clutch engages or disengages, the noise may be caused by an engine-related component. Probe the engine area with a stethoscope to pinpoint the noise.
5. Turn the ignition switch to LOCK (0) and check the drive belt for excessive wear, oil contamination, improper routhing, or a faulty belt tensioner (see «DRIVE BELT INSPECTION»(ref-333547-S27531885262009072100000) ). Correct any problems found. Start the engine, run the A/C system and check if the noise is coming from the drive belt, the belt tensioner or any of the pulleys. Repair or replace any faulty components.
6. Listen for noises coming from the A/C lines, the A/C hoses, the condenser, the evaporator, the receiver-drier or the expansion valve and check these items: Noises caused by A/C components touching other components or the body. Reroute or insulate the A/C components as needed and recheck for noise. Losee, damaged or excessively worn A/C components or mounting hardware. Repair or replace the faulty components or hardware and recheck for noise. A moaning noise from the A/C suction line. If there is a moaning noise, check the system refrigerant charge (see «System Charging»(ref-333580-S36054889922009072100000) ). If the refrigerant charge is OK, replace the receiver/dryer A whistling or hissing noise from the expansion valve. Evacuate the system for 3 hours (see «System Evacuation»(ref-333580-S03232597452009072100000) ), then recheck. If the noise is still present, replace the expansion valve (see «Front Expansion Valve Replacement»(ref-333580-S31995559902009072100000) ).
7. Check the operation of the A/C compressor clutch: Make sure compressor clutch engages without slipping. If the clutch does not engage, troubleshoot the A/C compressor clutch circuit (see «A/C Compressor Clutch Circuit Troubleshooting»(ref-333580-S14945424142009072100000) ). If the compressor clutch slips, replace the complete clutch assembly (see «A/C Compressor Clutch Overhaul»(ref-333580-S34490653552009072100000) ). Make sure the compressor clutch disengages. If the clutch does not disengage, do the A/C compressor clutch circuit troubleshooting (see «A/C Compressor Clutch Circuit Troubleshooting»(ref-333580-S14945424142009072100000) ). If the clutch circuit is OK, do the A/C compressor clutch check (see «A/C Compressor Clutch Check»(ref-333580-S21565573752009072100000) ), and see if the clutch is mechanically jammed. If there are no electrical or mechanical problems with the compressor clutch, replace the A/C compressor (see «A/C Compressor Replacement»(ref-333580-S23601001762009072100000) ). Make sure the compressor clutch cycles normally. If the compressor clutch is cycling rapidly, the A/C system if probably low on refrigerant dur to a leak. Do the refrigerant leak check (see «Refrigerant Leak Test»(ref-333580-S06379859662009072100000) ). If the refrigerant charge is OK and there is no leaks, troubleshoot the A/C compressor clutch circuit.
8. Listen with a stethoscope for noies coming from the A/C compressor and check these items: The noise changes when the compressor clutch disengages. If the noise does not change when the A/C compressor disengages, the noise may be caused by an engine-related component. Probe the engine area with a stethoscope to pinpoint the noise. The A/C system operating pressures are normal. If the system pressures are abnormal, troubleshoot the problem using the pressure test table in the A/C system test (see «A/C System Test»(ref-333580-S16855972072009072100000) ). Correct the pressure-related problems and recheck for noise. The compressor hose connections, mounting brackets and fasteners are in good condition. If any of these components are loose, damaged or excessively worn, repair or replace the faulty components and recheck for noise. If these components are in good condition and the noise is still present, replace the A/C compressor (see «A/C Compressor Replacement»(ref-333580-S23601001762009072100000) ).