KZ750 H2 ' relays for low and high beam headlight

I have measured the voltage at the bulb socket getting 10,5 volts for the low beam and 10 volts for the high beam.

I decided to install two microrelays to feed the H4 lamp and a new ground direct from battery.

I have trouble with the HEAD LAMP FAILURE light staying on (tachometer gauge), so it triggers the RESERVE LIGHTING MODULE - it gives the high beam only 3,2 volts to the high beam so you can continue driving in case the low beam burns out and meanwhile not blinding other vehicles. This 3,2 volt are not enough to trigger the high beam relay, but it keeps buzzing with annoying noise.

Does anyone know how the HEAD LAMP FAILURE system works?

+12 volts low beam cable triggers the low beam relay (always on because it is a US bike)
+12 volts high beam cable triggers the high beam relay
original bulb ground was left unused

undiablo wrote: Does anyone know how the HEAD LAMP FAILURE system works?

I'd wager it works like the brake light failure detector works: it looks for the bulbs filament resistance (which is like less than 10 Ohms) and signals a failure if the impedance is higher which would be an open filament. Disconnecting the light as you have done will also look like an open filament = failure detector signals.

undiablo wrote: ...Does anyone know how the HEAD LAMP FAILURE system works?....

On Kawasaki models equipped with a reserve lighting system -- in event of a headlight failure due to a blown filament in the headlight bulb, the reserve lighting system automatically switches the headlight beam from high to low, or vice versa, to (hopefully) instantly regain headlight function.

When automatically switching from low beam to high beam, a resister slightly lowers voltage to the headlight in order to keep the high beam slightly less bright and therefore less likely to "blind" oncoming drivers. Which might be an important consideration when riding at night where there's oncoming traffic.

Good Fortune!

bountyhunter wrote:

undiablo wrote: Does anyone know how the HEAD LAMP FAILURE system works?

I'd wager it works like the brake light failure detector works: it looks for the bulbs filament resistance (which is like less than 10 Ohms) and signals a failure if the impedance is higher which would be an open filament. Disconnecting the light as you have done will also look like an open filament = failure detector signals.

Thanks, but the positive wires for low and high beam are not disconnected. They are connected each one to a relay and work like a trigger signal. Please see the mod wiring diagram. However I have not measured the internal resistance of the relays... wich I supose would be different from 10 ohms as you say...

Could I place a resistor in that case?

undiablo wrote:

bountyhunter wrote:

undiablo wrote: Does anyone know how the HEAD LAMP FAILURE system works?

I'd wager it works like the brake light failure detector works: it looks for the bulbs filament resistance (which is like less than 10 Ohms) and signals a failure if the impedance is higher which would be an open filament. Disconnecting the light as you have done will also look like an open filament = failure detector signals.

Thanks, but the positive wires for low and high beam are not disconnected. They are connected each one to a relay and work like a trigger signal. Please see the mod wiring diagram. However I have not measured the internal resistance of the relays... wich I supose would be different from 10 ohms as you say...

Could I place a resistor in that case?

Thanks, but the positive wires for low and high beam are not disconnected.

They are disconnected from where they used to be connected.


Since the relay coil draws much less current than a headlight filament, it follows that it's resistance has to be a lot higher. Theoretically, you could add a large power resistor in parallel to drop the impedance but that burns power.

There has to be another way... may be Loudvx?

Well.... I give up. Thanks to all anyway. I hate to be beaten by astupid black box reserve light device