Symptom Related Diagnostic Procedures

A/C System, Odor Causes

Special tools, testers and auxiliary items required

• Ultrasound A/C Cleaner (VAS 6189A)

Odors from the A/C system can come from various sources. Only a portion of these odors come from the A/C unit evaporator and can be corrected by cleaning the evaporator.

Possible cause:

Smell like burnt oil.

• Mostly forms in the engine compartment due to leaks on the engine or transmission.

Sulphurous smell like exhaust.

• Due to leaks in the exhaust system.

• Through exhaust fumes, which get into the passenger compartment, for example, when driving in reverse through an exhaust gas cloud.

Fishy smell like coolant.

• If fishy odor is detected also in recirculated air mode as well as in fresh air mode, check A/C system heater core for proper seal.

• From leak at cooling system of engine or of A/C system heater core.

Smell like a burned clutch.

Evaporation from floor mats, decorative seat covers, etc.

Rotten, mildewy, moldy or musty smell from the front of the vehicle.

• Due to various contaminants, such as leaves, pine needles, etc. collecting.

• Due to water that cannot drain out of the air intake housing. Check the air intake housing water drains, refer to => [ Water Drain Hose ] Water Drain Hose.

Smell from air conditioner.

• Odors originating in the heating and A/C unit can mainly be detected in fresh air mode and recirculated air mode. If a smell occurs only in fresh air or recirculation mode, the cause is probably not the A/C unit.

• When the heater core is leaking, the odor of the escaping coolant can be detected in fresh air mode and in recirculated air mode (heater core has continuous air flow).

• Due to too much condensed water in the A/C unit. Check the condensation water drain hoses, refer to => [ Condensation Water Drain Hoses, Checking ] Testing and Inspection.

• Due to an old or dirty dust and pollen filter. Check the dust and pollen filter, refer to => [ Dust and Pollen Filter ] Service and Repair.

• Due to deposits on the evaporator fins. Clean the evaporator with the (VAS 6189A) => [ A/C System Evaporator, Cleaning ] Procedures.