Supersedes Technical Service Bulletin Group 87 number 14-54 dated August 28, 2014. There is an unpleasant, musty odor coming from the heating and ventilation system. The odor usually occurs when the vehicle has been sitting unused for five hours or more. The odor usually occurs within 20 to 60 seconds after the vehicle is started. Condensation, which is a normal condition in all A/C systems, can cause a musty odor. If the odor is noticeable in the vehicle when the engine is not turned on, the cause may be mold and mildew in the passenger compartment, and not be related to the A/C system. All other possible sources of the odor must be investigated before this bulletin can be performed.