BMW HVAC Blower Wiring Recall

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R. Scott King, BSME, Sr. Automotive / Mechanical Engineer ::::
Earlier this month, BMW announced it is recalling over 600,000 3-Series vehicles manufactured between 2006 and 2011 over concerns of potential fire risk. According to documents filed with NHTSA, BMW initiated this recall upon learning of a September 2017 incident involving a vehicle fire it deemed related to the heater and air-conditioning fan wiring. The defect, according to BMW, is the result of microscopic wear, or “fretting”, between the mating components of the electrical connectors. Over time, and with continued wear, electrical resistance between the mated connector halves can increase, resulting in excessive electrical current passing through the connector, which in-turn leads to excess heat. This heat first melts the plastic encasing the connectors, then in the extreme case, ignites it.
Notable in the NHTSA filings, however, is the investigative chronology associated with this recall. As those records show, BMW first became aware of this potential fire risk as early as a decade ago. Specifically, BMW investigated two incidents, one occurring in late 2007 and another in 2008, both “involving heat related damage to the heating and cooling system”. At the time, no root-cause of the damage was identified. Then, between 2010 and 2011, more incidents were reported and investigated. This time however, BMW concluded the root-cause was related to deterioration (fretting) within the electrical connections in the fan wiring. This finding led BMW to change to the metallurgical properties of the wiring connectors; however, the change was implemented in new vehicles only beginning in 2012; no modifications to the existing vehicle population were offered. BMW also indicates that between 2007 and 2014, it had received no reports of injuries related to this concern; however, in 2015, it learned of three such incidents. Continue reading “BMW HVAC Blower Wiring Recall”