Author Topic: Variable heated grips  (Read 6178 times)

Offline frankenduck

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Variable heated grips
« on: May 21, 2011, 09:05:53 AM »
The early K bikes' (and some Rs too) OEM heated grips have a resistive wire that the current runs through when you use the low setting.  This drops the voltage and reduces the heat from the grips.  The downside of this is that when used for an extended period that wire can heat up, melt it's insulation, short out and let some of the magic smoke out of the electrical system before blowing the number 1 fuse.  This happens to the intermediate wiring harness (part number 61121459263) that connects the switch and the heated grips to the main wiring harness.

This happened to me a couple of years ago.  I replaced the intermediate wiring harness but have not used the low setting since then because I don't want to risk this happening again so I just use the full setting.  Since I don't always need full heat from the grips it's a minor annoyance to have to be turning them on and off when it's only moderately cold.

The answer?  Get rid of the intermediate wiring harness altogether and replace the heated grip switch with a variable PWM switch.  PWM is pulse width modulation.  Instead of supplying 12V all of the time the switch varies the amount of time that 12V is output.  For example, a PWM set at 50% only delivers 12V half of the time, effectively reducing the voltage to 6V.

The OEM heated grips draw something like 50 or 60 watts so I found this PWM switch on Fleabay which has a capacity of 76 watts:
http://cgi.ebay.com/ebaymotors/PWM-dimmer-switch-12v-DC-LED-and-panel-lights-6-amp-_W0QQcmdZViewItemQQhashZitem1e6059cb44QQitemZ130465516356QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories#ht_583wt_911

The back of the circuit board already had some protective stuff on it but the side with the components did not.  With a toothpick I applied some epoxy to all of the exposed electircal connections on the front of it to make it water resistant/proof.

Then I mounted it in a carefully mutilated OEM switch blank and had to cut some stuff out of the handlebar cover from behind but was able to get it to fit where I wanted it

Here's what it looks like from behind:



I went through all of the 1/4" core knobs at McMaster-Carr to find one that I thought would work well with gloves on.  It looked kind of cheesy with a silver center so I glued on a city case roundel to gussy it up a bit.




I also epoxied a 3mm green LED into the top of the switch blank and hooked that up to the output.  It's gets brighter the higher you turn up the PWM switch.  I did that since this in kind of a prototype and the LED gives me visual confirmation that it's still working.




Voila! Variable heated grips. :D
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