Electronic Air Filter question

Hello, I purchased a house that was fitted with a Trane XR80 furnace, which was fitted with a Sears BP1 electronic/electric (not sure as to the correct term!) furnace filter. I have been unable to find any significant information regarding this filter. I was able to order replacement pads for it, but I have been noticing that, most often, indicator LED is orange/red, and I seem to recall that that means something is not working right with the filter. Does anyone have experience with one of these or even point me in the right direction to find a manual or information myself? Thanks!