Head light not working

[jyrki]

Hi,
headlight is not working.. if I measure voltage from connector before headlight it has 11 volts (high beam and low beam situations) but it will not light (H4). But if I connect same bulb directly to the battery of bike, bulb works (over 12 volts). What could cause that? Is it really the limit for H4-bulb that voltage, 12 volts? BR Jyrki

[ribbert]

Hi,
headlight is not working.. if I measure voltage from connector before headlight it has 11 volts (high beam and low beam situations) but it will not light (H4). But if I connect same bulb directly to the battery of bike, bulb works (over 12 volts). What could cause that? Is it really the limit for H4-bulb that voltage, 12 volts? BR Jyrki

The globe will work right down to 3 or 4 volts, it will just get dimmer as the voltage drops.

If you've got power (check it at the globe holder as well) and you know the globe works, the only thing left is a functioning earth. Run a wire directly from the headlight to a known good earth and see what happens.

I have heaps of these made up in different lengths all over the garage and in the tool kit on the bikes, it makes trouble shooting really easy by temporarily supplying power or earth to a circuit while leaving your hands free. On the road you can jury rig or bypass a faulty component with one (or hot wire the ignition if you lose the key) etc. Each one probably costs 5-10 cents to make.





Noel

[fj1289]

How does the starter switch interrupt power to the headlight?  Does it do it by removing the ground?

[Pat Conlon]

How does the starter switch interrupt power to the headlight?  Does it do it by removing the ground?

Yes, the starter button does interrupt the light...and the starter button has been known to partially stick.

[FJmonkey]

I fixed a non-working head lamp at a rally once. I all I did was jiggle the start switch.

[gdfj12]

The starter switch has 4 wires going to the body of the switch in the housing that terminate in 4 small contact pads. The starter button has a strip of copper in it that bridges one pair of the terminating pads at a time. In the default position, button out, the button completes the headlight power circuit and the starter circuit is open. In the depressed position it completes the starter circuit and the headlight circuit is open, allowing the amperage that the headlight would be using to help turn the starter.

I know this because I recently completed the conversion of my '89 to the later model 2 throttle cable set-up and couldn't source a 1991-1996 FJ RH switch housing, so I used an R1 RH switch housing that uses a simple starter switch, i.e only 2 wires going to it. I used a DPDT relay added into the merged wiring harness for the switch housing so that the plug would match to the FJ main wiring harness and would replicate the functionality of the FJ starter button. It works perfectly, cutting off the headlight when the starter is cranking.


George De

How does the starter switch interrupt power to the headlight?  Does it do it by removing the ground?

[jyrki]

Hi George, this sounds reasonable! Thanks! Next I need to open starterswitch and if there is something wrong..
BR Jyrki

The starter switch has 4 wires going to the body of the switch in the housing that terminate in 4 small contact pads. The starter button has a strip of copper in it that bridges one pair of the terminating pads at a time. In the default position, button out, the button completes the headlight power circuit and the starter circuit is open. In the depressed position it completes the starter circuit and the headlight circuit is open, allowing the amperage that the headlight would be using to help turn the starter.

I know this because I recently completed the conversion of my '89 to the later model 2 throttle cable set-up and couldn't source a 1991-1996 FJ RH switch housing, so I used an R1 RH switch housing that uses a simple starter switch, i.e only 2 wires going to it. I used a DPDT relay added into the merged wiring harness for the switch housing so that the plug would match to the FJ main wiring harness and would replicate the functionality of the FJ starter button. It works perfectly, cutting off the headlight when the starter is cranking.


George De

How does the starter switch interrupt power to the headlight?  Does it do it by removing the ground?

[jyrki]

Hi,
I checked starter switch, and it has only 2 cables. But there is some "coppercolour" depbris inside the switch, between four boles.. could that cause that there is allways some connections in open position (so that headlight would be off), but eventhough (third picture) there is in anycase 11 volts in final connections of the headlight... and bulb will not light.  If the voltage is not the only one needed?
Could that depris cause sortage of amperes through relay unit (where starter which is connected), which hinders headlight to light?!?!?