GM RVC Voltmeter Fluctuation By Dave Kaplan General Motors technical service bul- letin TSB-07-06-03-009 pertains to their RVC charging system and should be of interest to rebuilders and auto electric service shops. Subject: Information on voltmeter gauge fluctuation due to regulated volt- age control (RVC) system and concern about camper/trailer battery charging. Vehicles: 2005 to 2008 Cadillac Escalade; 2005 to 2008 Chevrolet Avalanche, Silverado, Suburban, Tahoe; 2005 to 2008 GMC Sierra, Yukon, Lester references 8292, 8301, 8302-140 amp. Condition: Customer may comment that the voltmeter is fluctuating between 12 and 14 volts (their vehicle is equipped with an RVC charging system). To improve fuel efficiency, the RVC system reduces the targeted output of the generator to 12.6 to 13.1 volts when in “fuel economy mode.” The generator exits this fuel economy mode when additional voltage is required. This mode exit and mode re-entry causes the voltmeter to visibly fluctuate between 12 and 14 volts. (The non-RVC system maintains a more consistent reading of 14 volts.) This voltage fluctuation with the RVC system is normal and no repair should be attempted. Camper/trailer owner concern: Some customers may comment that, while tow- ing, the auxiliary battery for the camper trailer will not stay charged. In most cases this concern is blamed on the new RVC system. If the tow/haul feature of the vehicle engaged then the charging rate will stay in the “charge mode” (13.9 to 15.5 volts). If the tow/haul feature is not engaged then the vehicle can enter the “fuel economy mode” which may result in a discharged auxiliary battery. Note: The RVC system will not go into the “fuel economy mode” when the head- lights are fully on; running with head- lights could assist in maintaining a charged auxiliary battery. Dave Kaplan is an engineering con- sultant with Wetherill Associates, Inc. Royersford, Penn.