What drives most drivers of these vehicles to distraction is the sometimes less than silky smooth take-offs, unexpected changes in HVAC output, and seemingly intermittent, hard-to-predict nature of the entire operation. Certain automakers have perfected the take-off while others still have a slight jerkiness to the affair. If the engine’s battery hasn’t fully recharged due to colder temps or heavy accessory demand, the stop/start won’t engage at all. The same can happen if the HVAC system is set to max cool or heat settings (especially cool). This is to prevent the cabin from heating up if the AC compressor was shut down with the engine. On some vehicles the parking brake can override and disable the system and none of them operate in reverse gear.
Almost all of these systems have an override defeat switch, but it has to be reset every time the vehicle is started by the driver. Countless owners of these stop/start vehicles have demanded a permanent defeat switch, but automakers have responded that it’s not legal as these vehicles were mileage-certified by government regulators with the system operational.
