Here's a little more information for the record.

For the interim period that I was searching for a used regulator, I designed a simple pushbutton regulator bypass. My design allowed the A/c system to operate normally if the car was not too hot (because my blower would operate in low to medium speeds, just not high speeds). If I needed quick cooling then I would push the button and full voltage would go to the blower. Once the car was cool then I would push the button again and then the current was sent thru the regulator. The pushbutton was tiny and I routed to the back of the ashtray. My carpool members said it reminded them of a James Bond 007 movie.

Also, to help you diagnose the regulator as the problem. You can use a voltmeter to measure voltage coming from the pushbutton controller. It should vary each time you push a button to increase blower speed till a max voltage of 4.5 (I think). If you see that, then you know your pushbutton controller is fine.

If you pass the above test, then supply full voltage to the blower by bypassing (ie., jumping) the blower regulator. If the blower operated at high rpm then you know you have a regulator problem.

Hope this is clear enough and good luck.

__________________
Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)