Red marking on a motor fan capacitor Red marking on a motor fan capacitor chicopee (Mechanical) (OP) 19 Jul 16 22:55 I used to know this but it has been at least three decades since I acquired that knowledge. Is the red marking on a Mallory capacitor (4MFD, 370V) to designate polarity? If so which one would that be? RE: Red marking on a motor fan capacitor ScottyUK (Electrical) 20 Jul 16 20:40 Possibly, it it is a DC capacitor. A photograph would help. From the description I suspect this is an AC film type which won't care about polarity.