How can I tell if my 1987 K100RT has heated grips?

Well, if they're BMW OEM grips then there should be a switch on the crashpad.

If they're installed correctly (mine weren't) then they'd be connected to the heated grips connector under the tank.

pseudotonal wrote:How can I tell if my 1987 K100RT has heated grips?

As far as I know Heated Grips are Gray, non heated Grips are Black.

If the original style are used, aside from the perhaps-not-obvious rocker switch in the dash pad, unscrew a bar end weight and look for the two fine wires from the end of the grip disappearing into the handlebar.

Thank you all for the help.  It looks like the grips are non-heated.

Oxfords are your friends!

My bike has oxford grips but also the oem heated grip switch beside the ignition which is redundant. Has anyone wired the oxford grips through the bmw switch so the oxford controller can be done away with?

Hi KiwiK100, I have used an OEM heated grip switch to control my aftermarket heated grips on my K1100 with no problems. Can't remember what brand the grips were as I installed them about 15 years ago, but they were not Oxford.
The factory grips have two heat settings controlled by the rocker switch on the dash pad, centre position being off, I think pushed down toward the rider is low heat and pushed away from the rider is high. I suspect that the lower heat is achieved by using a dropping resistor in a small intermediate harness that comes with the factory grips. I only used full 12 volt power to my aftermarket grips and switched them via the green/black (+12 volt from factory connector) and orange wires of the factory switch with the switch pushed toward the rider to turn them on.

The factory connector to supply power (green/black +12V, brown ground) for the grips is circled in the photo below (from my K1100 but it was in the same location and same coloured wiring on my K75 which I recently installed a second hand OEM set on).

Hope this is of some use.

Cheers

Thanks for your help Gaz80. I have the bike in a million pieces at present doing a complete restoration. The original harness is there so I will see how it all matches up when I put it back together. All the oem wiring for the grips is in the harness so it should be a simple case of modifying the Oxford connectors to to suit. The resistance is built into the intermediate harness as you mentioned, so I was just wondering if anyone had already done this.

It's very unlikely that you can substitute the OEM switch for the Oxford controller switch. I don't own a pair of Oxford grips but, looking through the online information, the controller contains solid state electronics that is not duplicated on the OEM switch. The BMW switch is a simple SPDT centre-off switch. You're stuck having to keep the Oxford controller.

As Rob says. I've had both and ditched the standard BMW heated grips in favour of a pair of Hein Gericke ones running from an Oxford Products controller. It's one of the older type with a rotary knob (not the newer digital ones that only give you four positions. Makes them just half as bad as the BMW ones ). The ability to select the exact heat setting is so much better.

Thanks all for your input. To be honest the Oxford are much better than the oem grips anyway, just don't like the look of the controller as I like things original.

I suspect the Oxford controller is simply a PWM (pulse width modulator) circuit. I would look to purchase a PWM controller like this http://www.ebay.com.au/itm/Pulse-Width-PWM-12V-24V-36V-DC-Motor-Speed-Regulator-Controller-Switch-3A-/181539908750?hash=item2a449f2c8e

The controller looks like a potentiometer. Find two settings on the potentiometer that provide the two levels of heat you want. Hard wire two resistors in place of the potentiometer that are selected with the OEM switch.

Thanks Kpilot, that gives me something to work on. I will post how I get on when I start putting her back together.

You can buy a PWM (pulse width modulator) on Fleabay for $3-4 and get variable heated grips. I've done that on several of my Ks and it works great.

KPilot wrote:I suspect the Oxford controller is simply a PWM (pulse width modulator) circuit. I would look to purchase a PWM controller like this http://www.ebay.com.au/itm/Pulse-Width-PWM-12V-24V-36V-DC-Motor-Speed-Regulator-Controller-Switch-3A-/181539908750?hash=item2a449f2c8e

The controller looks like a potentiometer. Find two settings on the potentiometer that provide the two levels of heat you want. Hard wire two resistors in place of the potentiometer that are selected with the OEM switch.

Why would you want to put resistors in a PWM circuit?  This makes no sense.

The crashpad switch would cycle between the two resistors (high - off - low). The pot hits the bin. I think I understand what you are saying, but finding two resistors that will disipate enough heat without the PWM circuit would be either near impossible or would take up a huge amount of space. They'd also need to be hung in the airstream.

I would also think that 3A is not high enough as most heated grips quote a maximum draw of 4A.

BTW: your PWM installation is far neater than mine. I have the Oxford box mounted snugly against the left handlebar switch.

duck wrote:

KPilot wrote:I suspect the Oxford controller is simply a PWM (pulse width modulator) circuit. I would look to purchase a PWM controller like this http://www.ebay.com.au/itm/Pulse-Width-PWM-12V-24V-36V-DC-Motor-Speed-Regulator-Controller-Switch-3A-/181539908750?hash=item2a449f2c8e

The controller looks like a potentiometer. Find two settings on the potentiometer that provide the two levels of heat you want. Hard wire two resistors in place of the potentiometer that are selected with the OEM switch.

Why would you want to put resistors in a PWM circuit?  This makes no sense.

I think I probably did not explain myself clearly enough. In the PWM system you have shown us in your post above, you have a potentiometer controlling your PWM unit (looks similar to the unit I linked to as well). My point is that you can use the potentiometer to set the pulse width and have a continuously variable temperature control, or you can keep the OEM look and use the OEM switch to control the PWM circuit. If you do this, you will lose the continuously variable temperature control and have to live with off/med/high. The switch would be connected to a fixed resistor array to set the pulse width in place of the variable resistor. 

Personally, the easiest way to run it is like you have done above, keep an OEM type switch for on/off and have the variable resistor that comes with the PWM on the crash pad to vary the temperature.

As I think about this some more, an easier solution to keep the OEM look and OEM switch would be to purchase two of the PWM controllers, they are only a few dollars each, and have the switch select one PWM or the other. This would be easier to wire and design than working the switch to control a resistor array. A smaller PWM here http://www.ebay.com.au/itm/HOT-Ultra-small-DC-3V-6V-12V-24V-35V-PWM-Mini-Motor-Speed-Controller-Switch-5A-/400982190126?hash=item5d5c66a82e

I may do this. I think you can purchase replacement oxford grips (as in no controller) reasonably cheaply.

Regards,

Chris

KPilot wrote:As I think about this some more, an easier solution to keep the OEM look and OEM switch would be to purchase two of the PWM controllers, they are only a few dollars each, and have the switch select one PWM or the other. This would be easier to wire and design than working the switch to control a resistor array.

I disagree. It's just two wires and two resistors. On the OEM switch the middle contact is wired to the potentiometer wiper pad on the PWM. One resistor is soldered to one side of the OEM switch and the other resistor to the other side. The 'loose' ends of the resistors are soldered together with the second wire. This wire then goes to the other potentiometer pad on the OEM board.

Downside? You still need an on-off switch somewhere else for the PWM board. You could use an OEM hazard switch for this job.

If you really are going to re-use the OEM switches then I'd advise taking them to pieces and checking the sliding contacts for corrosion. Just do it in a bucket as I can guarantee that the spring and plunger will make a dash for freedom.

[Edit] Also, looking at the controller you link to, I suspect that R1 (the big yellow resistor) is being used to dump unwanted power as heat. If so, it's a poorly-designed circuit.

Dai wrote:

KPilot wrote:As I think about this some more, an easier solution to keep the OEM look and OEM switch would be to purchase two of the PWM controllers, they are only a few dollars each, and have the switch select one PWM or the other. This would be easier to wire and design than working the switch to control a resistor array.

I disagree. It's just two wires and two resistors. On the OEM switch the middle contact is wired to the potentiometer wiper pad on the PWM. One resistor is soldered to one side of the OEM switch and the other resistor to the other side. The 'loose' ends of the resistors are soldered together with the second wire. This wire then goes to the other potentiometer pad on the OEM board.

Downside? You still need an on-off switch somewhere else for the PWM board. You could use an OEM hazard switch for this job.

If you really are going to re-use the OEM switches then I'd advise taking them to pieces and checking the sliding contacts for corrosion. Just do it in a bucket as I can guarantee that the spring and plunger will make a dash for freedom.

[Edit] Also, looking at the controller you link to, I suspect that R1 (the big yellow resistor) is being used to dump unwanted power as heat. If so, it's a poorly-designed circuit.

Hmm, you would have to draw me a diagram. I think the PWM uses a voltage divider circuit, not just a variable resistor. If you are correct, a second PWM circuit is still cheaper than an OEM switch (eBay PWM is about $3, OEM switch about 10 times that when I tried looking). OEM switch - off-self explanatory, position 1 powers one PWM circuit set at low, position 2 powers second PWM on high. If you were going to go with two controls, the suggestion above with on/off switch and a pot for temp would probably be better.

However, as suggested, there are plenty of options other than OEM or the Oxford controller.

KPilot's second idea is possibly the best -- two pwm circuits, each preset to give high and low heat conditions.

The PWM works by supplying the heating element in the grip with a square wave input.  The pot varies the on - off time, which delivers an average voltage to the element.  The ratio of the on - off times determines the heat out of the grip.

The OEM switch would be used to switch either of the PWM's outputs onto the heating elements.  You'd first find the pot setting that provided the desired heat level, then take the pot out of circuit and measure the resistances between wiper and either end.  Select two 1% resistors the values of which match the two measurements, solder two ends together and fabricate a JST connector with each resistor bridging a pin pair. Insert the new JST connector back onto the pwm card.

Then wire them in circuit.  Connect power and ground to the inputs, the motor- to one common connection between the heater elements, and motor+ from each PWM to the OEM switch.  The common connector of the switch would be wired to the remaining heater element leads.

Oh man, I'm starting to loose sleep over this  I was hoping for a layman's (easy) solution and fear I may well leave the controller on the cockpit where the PO put it. Electronics is not a sharp area for me, so short of a detailed drawing and a shopping list, status quo will remain, Been fun reading about it all though! There is a very helpful bunch of guys on this forum. Thanks

Here's another idea. It may or may not give good heat settings but it is simple.

Connect the heater elements in series for low heat and in parallel for high heat. This could be done using the oem switch.

I intend to try this when the weather gets cold enough to spur me into connecting up the parts I purchased last spring.