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Auto- On headlight?

  • Thread starter Thread starter MatBirch
  • Start date Start date
M

MatBirch

Guest
I know this has come up before, but I don't recall seeing a resolution.
My wife rides a 1980 550l. It has an off switch for the headlight. I don't like to have her cranking it with the light on, but she tends to forget to turn it on after. She's just a beginner, and I stress out bad enough when all goes well. Even with the light on, she tends to disappear into the landscape, so when she forgets, it ain't good. My old Honda CB750, and my newer, old BMW both have automatic ON lights, that cut out while cranking. Short of buying a set Honda handlebar switches and grafting it all in, is there a way to relay the setup we currently have ?

i'm hoping it's as simple as an N/C relay between the power wire for the headlight and the button for the starter?

Any help would be greatly appreciated!
 
I have two of my four GSes wired to cut the headlight power while cranking.

Takes a 5-pin relay, be sure to look for one with an 87a pin. (Some of them have two 87s.)

The 87a is normally closed (N.C.), so it will pass current from 30. If you connect 85 and 86 to the starter terminal of the solenoid and ground, the relay will be activated when you push the starter button. That will cut power to the headlight, which will resume when you release the button. To keep wires short, I interrupted the power wire from the LIGHTS fuse to the headlight switch right near the fuse box, which is conveniently close to the starter solenoid. If you want to get a little 'creative' with the wiring, instead of connecting pin 30 back to the LIGHTS fuse, connect it to the battery with its own fuse. That will reduce some of the losses incurred by going through the wiring to and from the ignition switch, back to the fusebox.

.
 
Steve said:
I have two of my four GSes wired to cut the headlight power while cranking.

Takes a 5-pin relay, be sure to look for one with an 87a pin. (Some of them have two 87s.)

The 87a is normally closed (N.C.), so it will pass current from 30. If you connect 85 and 86 to the starter terminal of the solenoid and ground, the relay will be activated when you push the starter button. That will cut power to the headlight, which will resume when you release the button. To keep wires short, I interrupted the power wire from the LIGHTS fuse to the headlight switch right near the fuse box, which is conveniently close to the starter solenoid. If you want to get a little 'creative' with the wiring, instead of connecting pin 30 back to the LIGHTS fuse, connect it to the battery with its own fuse. That will reduce some of the losses incurred by going through the wiring to and from the ignition switch, back to the fusebox.

.
Click to expand...
If implemented as you describe the lights would be powered directly from the battery through a relay, but they would always be on. The solution I posted provides what you are suggesting but with only one 4 pin relay (lights are powered from pin 87).
 
Not to be disagreeable, but there is also the option of just leaving the lights on when you crank the starter. If the battery and charging system are both good, having the light on (even on high beam) makes very little difference in actual starter performance. At least, that's been the case on the bikes I've owned.
 
posplayr said:
If implemented as you describe the lights would be powered directly from the battery through a relay, but they would always be on.
Click to expand...

You are quite correct, sir. :oops:

I had forgotten that I actually have mine powered from a relay that is controlled by the ignition switch, not directly from the battery.

In fact, my whole fuse box is powered by that relay, so the only current that goes through the ignition switch is what little it takes to activate that relay. With that and the new (Eastern Beaver) fuse box, there is virtually no voltage drop on the bike any more. :encouragement:

posplayr said:
The solution I posted provides what you are suggesting but with only one 4 pin relay (lights are powered from pin 87).
Click to expand...
The problem I have with that setup is that you are relying on a relay to power your lights. If the relay fails, you have no lights. Using a relay with an 87a terminal is fail-safe, you are using the relay to turn the lights OFF.

.
 
Steve said:
You are quite correct, sir. :oops:

I had forgotten that I actually have mine powered from a relay that is controlled by the ignition switch, not directly from the battery.

In fact, my whole fuse box is powered by that relay, so the only current that goes through the ignition switch is what little it takes to activate that relay. With that and the new (Eastern Beaver) fuse box, there is virtually no voltage drop on the bike any more. :encouragement:


The problem I have with that setup is that you are relying on a relay to power your lights. If the relay fails, you have no lights. Using a relay with an 87a terminal is fail-safe, you are using the relay to turn the lights OFF.

.
Click to expand...

Steve, powering the lights off of a relay is no different that any of the multitude of relay mod variations including your BeaverBox Mod. That is the whole point of a relay mod. Of course you are correct, mechanical relays are not the most reliable and the SSPB is an alternative to eliminate the mechanical relays.
 
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my 650 has no light switch but I miss it. So... I interrupt the fused headlight circuit with a NormallyClosed relay and actvate it with a tap on the starter circuit- not the solenoid or the handlebar button-,but the actual starter....

There's a small "relay delay" I suppose caused by "collapsing fields" of the starter (ie: when a coil shares a circuit with a relay's coil ,but anyone experiencing it can look into "clamp diodes").
 
A 550 cranks as easily as a sewing machine, there will be zero problem with cranking it with the light on. Your battery could crank 3 550 engines at once with no problems. Have her leave the light on and save your worrying for something else she's doing, it's just not a concern.

On my 550 I absolutely can't tell any difference between cranking it with the light on or off. It just doesn't matter.
 
In my experience, if your GS, regardless of displacement, doesn't fire up well within 3 seconds, something is outta' wack.
 
tkent02 said:
One second unless it's been sitting a month in below zero (F) temperatures.
Click to expand...

Agreed. I was using three seconds as an absolute maximum.

In good tune, all you have to do is THINK about pressing the start button.
 
Yes, I agree with you.

Still, the headlight interruption is.... elegant. A bit less voltage drop for the coils and startermotor on his wife's bike -that could be useful .

Whichever, on bikes with a "real" switch, I have forgotten to turn them back on too , every so often, and that's definitely a bad thing
 
It reduces the electrical load by 1/2. Of course that might only be 10% of the starter load. On bigger engines it does make a diff.
 
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