Hello,

When I first got my 300D/W123 (used), it seemed like the heat worked pretty well, even at normal streets speeds in the 30's. It worked really well up at highway speeds, producing a decent amount of heat for the cold northwest winters.

Recently however it seems like my heat has diminished and hardly even works at street speeds. I have to really be cruising at highway speed for a while to feel any heat at my vents.

I've heard other owners say their heat was almost "nuclear" and "vent melting", so I'm wondering where to start diagnosing the problem with my heat. Could it be as simple as the "auxilliary pump" next to the dreaded automated valve thing? What's the most likely cause of this recent change it perceived heat production?

Thanks much for your input....