Headlamp Relay for Custom Wiring Harness

[peterg]

I've done quite a bit of research on this and am looking for confirmation.
Below is the schematic for the Stock Safety Relay I lifted from 650rider.com. The relay coil is feed from the Stock alternator's 6V yellow wire. Once the motor is running and the headlamp is on the headlamp relay coil is kept closed by the headlamp feed via the resistor. This ensures that the headlamp stays on in case the alternator power dips.

Below is my understanding of how a Headlamp Relay should be connected in a custom application. Since I'll be using a PMA, which does not have a 6V lead, the relay coil needs to be feed by one of the PMA's wires that feeds the R&R. Since this voltage is in excess of 12 volts feeding the relay coil through the headlamp power via a resistor is not needed.

Makes sense? Or am I completely out to lunch.

 

[Jim]

That's gonna be an AC output from the PMA. As long as the relay is compatible with AC power, it should work. If it wont take AC, you could put a diode on the PMA line to pin 86. Would give you a pulse DC.....

 

[peterg]

Thanks Jim. Makes sense.

 

[Jim]

Thinking more on this.... if you use a DC relay, you'll prolly get a bit of chatter with the pulse DC. Could add a small capacitor. Might have to play with the size....

 

[peterg]

As long as the headlamp does not turn on before the starter motor has started the engine and the headlamp stays on as long as the the engine is running does a bit of chatter matter? The PMA is only feeding the relay coil and not the headlamp.

 

[Jim]

Well since you're not using batt. pwr. through a resistor to "latch" the relay the way the original system did, the chatter would make the headlight flicker.

 

[gggGary]

the chatter would make the headlight flicker.

KOOL, OLD SKOOL! All us old guy guys remember flickering dirt bike headlights.

 

[Eotnak]

4 diodes aka bridge rectifier and a capacitor should do the trick.

 

[5twins]

The original set-up will (and does) turn the headlight on before the motor starts. If you crank the motor over enough to start generating some charging output, the relay will trip and the headlight will come on, even before the motor is running. That's one of the things I don't like about this set-up. When you let off the starter button, the headlight remains on even if the motor hasn't started. Then you have added draw on the battery for your next start attempt. The only way to turn the headlight off again is to recycle the key switch to off then on again.

 

[peterg]

Sounds like the best solution is an on/off switch for the headlamp and a warning light lit when the headlamp is off. Since I will be using a stock switch which is an on/off type I will need a relay to turn off the warning light when the headlamp is off. Is there any concern about chatter in this application?

 

[Jim]

Is there any concern about chatter in this application?

Nope.

 

[mike in idaho]

Here is a circuit to turn on the lights with the neutral switch: http://www.geocities.ws/loudgpz/GPZheadlightTrigger.html

 

[Jim]

If all you want to do is kill the headlight during start, just use the starter power to de-energize a relay powering the headlights.
I drew this up a while ago to de-energize the alternator during start. Just run the relay contacts to the headlight circuit instead of the alternator....

EDIT: Better yet, use a double pole relay and disable the headlight and alternator both during start....

 

[Jim]

Like this.....

 

[peterg]

Jim. That's a good solution. Could the starter switch ground wire L/W be used to power the new relay coil instead of the starter motor power? I will not be using a safety relay. The starter solenoid coil will be feed from the battery via the key switch.

 

[Jim]

Could the starter switch ground wire L/W be used to power the new relay coil instead of the starter motor power?

You could if you ran the solenoid and new relay in series. Not sure how the added resistance would affect the solenoid though. Using starter power is probably your best bet.

 

[peterg]

The issue is powering the coils of the starter solenoid's and the headlamp relay's coils from the same power source? The start button would ground both the solenoid and the relay. This is my understanding of this circuit:

 

[Jim]

That would work.