[hi-ho_silver]

So this may fix the surging blower fan motor then? Hmmmm...

 

[hi-ho_silver]

According to service manual the ECM turns alternator charging to its highest charging rate during coasting,deaccelerating, and braking.

That matches when I hear the blower get faster. I notice it most when the blower speed is set to half way or more in the truck, otherwise it is too quiet to hear over the radio etc. I may give it a try this weekend and see what happens.