> Replacing the O2 sensor with a Bosch 13913 3wire universal on my 91 80Q, of > the 3 wires, I know black is signal but the preheat + and - are both white, > does the polarity matter? the polarity does not matter on the heater, no. -- Huw Powell http://www.humanspeakers.com/ http://www.humanthoughts.org/