Add PWM speed controller switch to Fantastic Fan Vent

Primarily to slow down & quiet fan it also adds variable speed instead of 3. Additional plus is fan will consume less power at slower speeds verse stock. Factory switch uses wire wound resistors that decrease voltage to fan by simply burning off voltage as heat to slow fan down.

Simple project that has been on the round to it since I bought PWM switch a year ago... I used A RioRand15 amp unit mostly due to better than average reviews, remote adjusment knob-for as long as link lasts Amazon link 15 amp PWM

This is on a basic 3 speed fan that has reversing switch. No rain switch, thermostat or power lid. I set up so that fan can easily be reverted back should issue arise. Also wiring the 3 speed switch as power supply for PWM gives you a positive off switch. PWM controller I used does not have an off or reversing ability.

Note: duty cycle rating if shown, lower rating is how slow it will go, IE 10-100% means all they way down 10% power still applied. Some PWM controllers have an off position. Some rated at 0%-100% can still apply millivolts when fan appears off. Some folks use the center off position of reversing switch to turn off power to fan motor, however PWM controller may still be energised. Hence I wanted a positive off switch BEFORE the controller.

There are as many ways to wire in PWM controller as there are PWM controllers.. Just how I did ours.

FYI if you don't have a reversing switch your output would go directly to motor. I dropped fan to add new controller. NOTE which color wires go to which terminal if you have reversing switch. Wont hurt if not replaced in same position but fan will turn opposite of what switch says if swapped.

Basically existing 12v+ from camper to fuse and then to 3 speed switch are the only wires left intact.

Camper ground that previously went directly to reversing switch/motor is now run directly to PWM controller. Ground out from controller then goes to where ground previously went, reversing switch or motor. From what I've read, not removing chassi/camper ground from motor and not running thru PWM controller is most often error folks make setting this up. Ground must go thru PWM. There should be NO common ground connection back to chassis/camper after PWM controller or to motor. It wont work or speed wont be controlled...

Power wire that went to motor from 3 speed switch is disconnected at both ends. New wire from constant power lug of 3 speed switch now run to PWM controller. From controller it then goes to motor (thru reversing switch).

Note: any testing after installed, both the ground and power go thru PWM controller to control speed. I used light bulb to verify it was working but had ground connected to the input ground, before the controller- bulb never dimmed-duh.
Second is the reversing switch, I don't know for certain but it seems possibly turning it off to change direction may not be a good idea on the PWM controller. Disconnecting load from output of PWM might back feed? So Ill turn off power switch first, then change direction switch after blade stops spinning.

Something so simple trying to relate makes it convoluted. Just some pictures I took along the way.

Black wire that runs between factory 3 speed switch and reversing switch is unplugged at both ends, no longer used. Stock ground wire is also disconnected from camper ground, a new longer ground is run to new PWM controller. I left original ground wire, tucked out of the way, for future reconnection if needed.

Might be easier to replace with simple on/off switch but again I want ability to return back to factory should PWM fail

Again only wire unchanged is the one from camper 12v+ to fuse and from fuse to 3 speed switch. The center lug when 3 speed switch is turned to any on position, is powered with full voltage, using to power PWM controller.

PWM speed knob mounted, I extended wires 3" to place where more easily reached. Drill hole (mIne was 17/64" for shaft and a small 7/64" blind hole for anti rotation tab) convenient

Used a hot glue gun to secure wires and PWM controller.

Just for my reference. I scribbled on the fan but just to document restoring factory switch.

All that's left is to reinstall and hope I can't hear the PWM. Common is frequency of PWM is audible, some quiet loud. Fingers crossed..

Not shown is the fan housing on ceiling. There is a screened hole, I assume to let the heat of stock 3 speed switch out. When I removed the fan face the switch and the corner it resides was covered in dirt & debris. The 'heat' escape hole is open to outside when vent lid is up. I'm closing off the hole.


Re Labeled later after putting on glasses-WOW those letters are big plus I had left original sticker on and it showed.

Hmm lettering was orientated reading upside down-same as original speed numbers, opposite what reversing switch was. Curious that lettering would be orientated different. Always hard to see IN/OUT as faced toward bed and angled to trim garnish. Doh pulled switch and reversed so same orientation, much easier to read. Note to self- swap motor lead positions:)

Anyway installed and works great. Put up short video, about half way thru can 'hear' the fan. Link if embed doesn't show

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