blower motor won't shut off

[WANT '71 280SEL]

I've done a search, and there were two previous psosts by others, who posted no results, and received no answers, so here it goes.
I replaced the blower motor regulator with a used one that I bought off a member here. Now, the car hasn't had a blower in about 5 months, and it has alwats been driven regardless. I'm fixing it now because defrost is useful. Anyways, all the buttons work on the PBU as they should, as does the temp. wheel, but when you turn it off, the motor goes to low and it cuts off the water to the core. So it blows outside air at low speed when the "O" button is pushed. Once you turn it on, by selecting and of the positions, it will warm up or cool down and adjust the fan speed accordinly, do you guys know what could be wrong? I've had the aux. water pump disconnected for awhile now because it went bad, but that wouldn't affect this would it? Is this a symptom for a bad PBU or was the regualtor I got bad? I thought the regulator either worked or it didn't?
Thanks
David