'99 S420 climate control blower fan stays on, even when car is turned off

[Herplaw]

Greetings, my first post upon joining;

I have a '99 S420. A couple of months ago my blower fan died. I was told at a dealership my blower fan and blower regulator both needed to be replaced. I got a used blower and new, aftermarket regulator. Worked fine for 2-3 months. Yesterday, when I parked the car at work, the fan continued to run, even after the car was turned off. Battery was dead by noon. After a jump, on the way home, I tried auto, off, adjusting the fan up and down, defrost, etc, all to no avail. When I parked at home, the fan continued to run. It stayed on until I disconnected the battery.

One dealership says that there is only one regulator available for that car, all options. Adsitco says that there is one regulator for cars WITH activated carbon and a different one for cars without. Mine has the carbon filter.

Does this sound like a regulator issue? Are there more or different regulators, other than 140 821 8451?

Is there anything else that I should look at? The Climate Control relay? the dashboard control panel? How do I (my local mechanic) check without buying and replacing part after part?

I am over 100 miles from any dealership and hate to pay dealership prices ($350 for the regulator) when Pelican has 4 of them, ranging from $87 to $338.

any and all assistance and comments welcome, where do I go from here?

Jake