LED brake lights cause Cruise Control to stop working

[WingAdmin]

Once in a while I learn something new. Actually, I learn new things all the time, but this one took a bit of doing.

Over the winter, I replaced all of my rear lights with custom LEDs. I got everything together, and on my first ride out, discovered that my cruise control no longer worked. It would turn on, but ignored my pressing the "Set" button as if it wasn't even connected. The cruise control has always worked 100% before, so I had to assume something I did caused the problem.

I pulled the trunk off and took the cruise computer out. I hooked up a meter to the connector and tested all the signals from the various switches - brake, clutch, throttle disengage, and so on. Everything checked out 100% correct. I then had a look at the circuit:

Cruise Control circuit diagram

The cruise computer monitors the brake lights - it has a connection right to the same wire that is turning the brake lights on. This is so it shuts off immediately when you hit the brakes. You hit the brakes, it sees +12V on that green/yellow wire, and shuts the cruise off. I started thinking - what if that wire needs to be pulled to ground in order to activate the cruise? Normally, it would be pulled to ground through the filaments of all the brake light bulbs. What if the various LEDs I had installed weren't presenting enough of a ground to allow the cruise control to activate? I decided to try an experiment. I added a SPDT relay to the circuit, so that when the brakes were not applied, the cruise control saw ground, and when the brakes were applied, the cruise control saw +12V:

Modified Cruise Control circuit diagram

I reassembled the bike and took it out for a test ride - and the verdict is, the cruise control now works again. So my hypothesis was correct: The cruise control not only disables itself when it sees +12V on the green/yellow brake line, it disables itself when it sees ANYTHING other than ground on that wire - and a floating input counts as "not ground".

So if anyone replaces their brake lights with LEDs and finds they can no longer set their cruise control, this is the solution.

[ka4yqi]

Thanks, yoU may have saved us a bunch of hair pulling. That somthing I can't afford to give up much of. I llike to change out my lights to leds in the future. Thanks again..

Steve

[cbx4evr]

What do you mean by "custom LED's"? I replaced my brake light bulbs with the eBay China LED bulbs you recommended some time ago. Haven't noticed any problems with the cruise.

[RBGERSON]

suggest this goes to a how to article..after a bit of time here.

[WingAdmin]

What do you mean by "custom LED's"? I replaced my brake light bulbs with the eBay China LED bulbs you recommended some time ago. Haven't noticed any problems with the cruise.

Custom LEDs as in I tore all of the lights apart and installed LED strips in all of them, instead of using LED replacement "bulbs."

LED strips installed inside lens

[thrasherg]

I would suggest, rather than going to the complexity of wiring in a relay, to just connect a resistor from the green/yellow wire to ground, use something like a 1K 0.5W resistor, that way there is negligible current flowing, but it will pull the wire to ground. Should be a lot easier and cheaper than a relay to install.

Gary

[WingAdmin]

I would suggest, rather than going to the complexity of wiring in a relay, to just connect a resistor from the green/yellow wire to ground, use something like a 1K 0.5W resistor, that way there is negligible current flowing, but it will pull the wire to ground. Should be a lot easier and cheaper than a relay to install.

Gary

That was going to be my original fix. I originally tried putting a 470 ohm 1/2 watt resistor in there to pull it down, but it wasn't enough - it was still keeping it disabled. I knew 1157 brake light filaments are 21 watts, and that the OEM bike has two of them, so that's 42 watts, or 3.5 amps, which works out to around 3.4 ohms. I had a 100 watt, 4 ohm power resistor, and was going to stick that in there, but the brake sense wire on the cruise ECU was very small - looked like 28 gauge, and nowhere near enough to handle the 3 amps that resistor would draw. I could have stuck it elsewhere on the brake light circuit, but then I would have had to find a place on the frame to sink the fairly large amount of heat it would produce, without melting any ABS bodywork.

I figured I could easily switch the cruise ECU input line between ground and 12 volts, without having the hassle of dealing with heat dissipation (not to mention wasting 3 amps of perfectly good power as unwanted heat) by simply using a relay - so that's what I did.

[thrasherg]

So what is causing the green/yellow wire to float to 12 volts? If you need less than 500 ohms to pull the wire down, it's not really floating, something is supplying significant current to hold it high!! Given that a 480 ohm resistor was insufficient, then your relay looks like the best solution, but I would have expected a 1K resistor to be sufficient!! If I had the same bike I would be digging in a bit further to find what is supplying so much current that the 1K could not discharge the wire!! But your fix is just fine, but more work than I would have liked!!

Gary

[WingAdmin]

So what is causing the green/yellow wire to float to 12 volts? If you need less than 500 ohms to pull the wire down, it's not really floating, something is supplying significant current to hold it high!! Given that a 480 ohm resistor was insufficient, then your relay looks like the best solution, but I would have expected a 1K resistor to be sufficient!! If I had the same bike I would be digging in a bit further to find what is supplying so much current that the 1K could not discharge the wire!! But your fix is just fine, but more work than I would have liked!!

Gary

It was 470 ohm, not 480 - typo (now fixed).

Also keep in mind that it's the 470 ohms plus whatever the resistor value is to run the LEDs off 12 volts (or current regulator, or whatever it is they do in there).

It only took me 15 minutes or so to rig up the relay, and I really just wanted to get it done and working, so I was happy that it was working.

[Erdeniz Umman]

Here is the link describing the solution for this problem?
http://www.goldwingfacts.com/forums/2-g ... olved.html

[WingAdmin]

Here is the link describing the solution for this problem?
http://www.goldwingfacts.com/forums/2-g ... olved.html

That is something a little different. He's describing where a single LED is being used for both running and brake lights, and he is using a resistor to limit the current for the running light, to make it dimmer (not the right way to do it, BTW). The problem was that the resistor was allowing current to back-feed the brake lights, and trigger the cruise shutoff. In that case, using a diode (like he did) will fix the problem.

My assumption was that having the brake light wire at ground would be fine for the cruise control - not so. It must be FLOATING. If the cruise control sees anything other than floating (i.e. +12V or GND or anything in between), it cancels the cruise control.

[Erdeniz Umman]

Here is the link describing the solution for this problem?
http://www.goldwingfacts.com/forums/2-g ... olved.html

That is something a little different. He's describing where a single LED is being used for both running and brake lights, and he is using a resistor to limit the current for the running light, to make it dimmer (not the right way to do it, BTW). The problem was that the resistor was allowing current to back-feed the brake lights, and trigger the cruise shutoff. In that case, using a diode (like he did) will fix the problem.

My assumption was that having the brake light wire at ground would be fine for the cruise control - not so. It must be FLOATING. If the cruise control sees anything other than floating (i.e. +12V or GND or anything in between), it cancels the cruise control.

Wing Admin
I rarely join in this forum, just wanted to share what I have found out about the cause and the solution for the "LED bulb cancels Cruise Issue".

From your post I understand that you misunderstood some points.

I did not say anything about a single led in that post. Instead I described the problem in a 1147 LED bulb which has 27 LEDs on it.

That is not my preference either, but most of the LED bulbs work in this way to dim the bulb, which may Cruise Control Problems.

First problem that I have found in these LED bulbs is the incorrect usage of 1/4 watt resistor which causes overheating. I replaced the built in resistor with a high wattage one, and gave the test results in that post.

And the second problem that I have found is, the voltage leak between the leads of the 1157 led bulbs. Since tail and brake lights use the same point inside the LED bulb case (not like separate filaments in a regular bulb), when voltage is applied to the tail light wire it will leak into the brake light wire, as if we applied the brakes, this positive voltage will go to the Cruise Control Unit and will cause the cruise control to disangage or never engage. To solve this problem I added a diode between these contacts inside the bulb case.

Actually I added two diodes, since my bike is a EuroSpec GL1500SE, which has an on/off switch for the head and taillights. I added the second diode because when I applied the brakes, when the head and taillights were off, I observed some voltage leakage as well, which caused instrument panel illumination lights (They are LED by the way) to come on. And the second diode prevented this voltage leak. For US Spec bikes this is not necessary though.

And in that post I also explained how to find and buy a correct LED bulb which has built in diodes, not to encounter any Cruise Control Problems.

[darryldevaney]

I came across this article the other day after spending the weekend riding with a friend who had installed LED lights on his Victory Vision and was experiencing the same exact issue with the loss of his cruise control. I forwarded this article to him and it proved to be valid on his bike as well. He didn't have any relays on hand so tried using a load balancing resistor left from his LED installation instead and it fixed his issue. I haven't analyzed the effects of that versus WingAdmin's solution but just wanted to share an alternate solution.

[William Hopgood]

It would be really nice if you could include some pictures of your relay or diode or resistor or maybe even a video I'm reading this diagram and it seems like it's written in Spanish so I guess if you could add a picture or maybe a instructional video that would be awesome