Unless you live in Gnome, Alaska, I'd bet the problem is elsewhere. The aux pumps are notorious for dying in place, and you never really notice it unless you're in a seriously cold place. Mine was dead for over 4 years on the TE and we always had heat. My 1980 300D had crappy heat, but that was because I had crud in the heater core that I was never able to flush out. The aux pump on that car never worked the whole time I owned the car, so I know that wasn't the problem.

HTH,

someguyfromMD