It's just a pure guess, but is the zener a fairly large one? - it could well be an 18V 2W zener, to help keep nasty big spikes out. If this is the case, it should be directly across the incoming 12V supply - probably after various filtering components.Clinton said:I'm in the process of repairing my Digital Dash and have found the defective part. The part in question is a Zener Diode, and unfortually the only markings it has is 18 and under that 2. Does anyone know what type of Zener this is.