Every time I turn on the defroster for my 2003 Ranger and the AC pump engages you hear the engine drop a cylinder (no spark). When it disengages, the cylinder drops again. The voltage in the battery only drops .02 volts and the AC still blows cold. The defroster works fine. No tripped engine code or check engine light. Just sounds rough when idling with the defroster on. Defroster off, there are no dropped cylinders.