[Wavey]

Sorry to hear about your trouble with this Ian - must be driving you nuts.

A couple of things:

Is this the only electrical problem with the car? I wonder if your alternator/regulator are weak - do any of the lights get brighter with increased RPMs? Of course your footwells worked OK before the change so probably not.

I *think* the engine compartment controller is under the black cover near the rear fuses.

I have disconnected my footwell blowers because they need new motors, but I'm pretty sure they never ran in the "0" position.

Per the diagram, it seems that the problem would almost have to be in the variable speed switch, or the resistor pack, or due to a bad ground. But again, everything worked normally before so this is indeed confusing. I can see why you'd think it's due to the Grainger motor, but my footwells worked normally until the motors got really noisey (which they were before the Grainger motor replacement). I cleaned and lubed them and they were fine for a while then got noisey again, so I just pulled the fuses.