After installing a bilge blower in my bus as described in other heating improvement articles to be found at:

Bilge Motor Installation

http://www.type2.com/library/heating.htm

I was very pleased with the results, although I also discovered that the sound level was about to drive me nuts (however it was more tolerable than my putting up with less heat).

I considered several options as a solution, and determined that speed control was the most viable.

After much searching, I found this DC motor speed controller kit, which is a unit designed specifically for the purpose of adjusting small DC motor speeds, and is available for less than $20 including shipping, at the following website;

http://www.circuitspecialists.com/prod.itml/icOid/3349



The one catch, is that the unit is in kit form, and must be assembled. They say it requires basic soldering skills, although I found it to be a bit intricate, and would not recommend anyone to attempt assembly without prior experience, or some help. However, with the necessary skills, it works like a charm. One thing to consider, is that the circuit uses sinking technology, which means the ground wire (black lead to the motor) must be dedicated (a separate wire of it's own), without connection to the chassis. Controller wiring is very simple, requiring positive and negative wires to supply power to the controller, and two other wires supplying power from the controller to the motor. I suggest using a positive power supply lead that is fed from the ignition switch running position, and is fed through a switch dedicated to shut power off to the controller.



I searched all over for an assembled unit, but have not found anything apart from much more expensive ($100+) industrial units.

The controller works so well (no more screaming whine, and yet ample heat), that I installed another blower with controller, as a makeup air unit, that supplies not such freezing air (from the interior) to the engine compartment to help recirculate heat, which I found out works much better than I expected. I intend to address that installation in another article.

I mounted both controllers just above the passenger side heater vent with 2" wide Velcro strips, and extended the potentiometer leads from each board to the dash, so I can easily control their speeds.









Yes, it's a bit of work, but to me it sure is worthwhile. As for the elsewhere mentioned problem of having too much heat, I have yet to experience such a problem, and suspect the comment was made, tongue in cheek, although comparatively, the blower(s) really is (are) a major improvement.