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Good morning!

I have been trying to figure out the operation of the low/high headlight and the left hand switch. Using the Ducati Workshop manual, I am following pg 41 Operation of headlight switch. With the key off and position 1, the running light, green light and rear lights come on. When inserting key, position 1 works and rear brake light functions. When in position 2 with key in I do not get the headlights to come on, will the headlight only work with the bike running? I can not get 6v to the white wires with key in and bike off. Possibly bad diode?

Also, where both white wires come in, only one position will allow headlight to work when jumped directly to 6v, the other leg doesn’t. It doesn’t appear the bulb is bad, other ideas?



The wiring diagram I am following is from clymer manual pg 33 160 Monza Jr, this doesn’t show the red and green light in headlight bucket.

The typical schematic diagram of an Italian light switch is of no real value. It does nothing to convey where power is supposed to be directed by the rotations of the switch.

Since you have a battery, you are not dependent on the engine running to supply power to operate the headlight bulb.

Seemingly, with a working switch it looks to me that node #7 on the switch is likely the power feed to the switch, and the switch will direct power to either node #1 or #2 for low beam or high beam operation.

If the battery is uncharged or weak, a working switch may look faulty as the high amperage requirements of the headlight filaments might need more power than the battery can deliver.

If you have a good 6-volt power source (a fully charged 6-volt battery, a 6-volt battery charger, or a 6-volt power supply) it would be useful to test the headlight bulb (both high and low beam filaments) outside of the motorcycle's wiring to assure yourself it's not a bulb issue.

It looks like the gray and blue wire meeting up at the headlight socket terminal would be the "ground" wire. Run a wire from your known good power source to that terminal and tap the other wire one-at-a-time to the terminals on the bottom of the bulb (the ones that the curved copper pieces are touching in the picture.) The headlight should light when power touches either terminal.

If the headlight is good, without the headlight connected I would use a voltmeter to check that power is going to the switch and then I would set the switch in all possible rotations and make a chart of which of the two white wires coming off of the switch have power for every rotation of the switch.

I'm suspicious that your motorcycle has been rewired. Having a white wire for high beam and a white wire for low beam is confusing. Also, the gray wire and blue wire both being used at the same electrical node lends to confusion when wiring and debugging the electrical system. It seems like the bike was rewired with the wire that was on hand after not being able to source or wait for the correct wire color(s) to be purchased.


Jim

If your Monza has been wired as per the circuit diagram, then the following will apply;

The alternator will drive the headlight and tail light with A.C.
The battery will feed the horn, brake light and parking lights.
The ignition is independant of the battery and is driven from a separate coil in the alternator.
The diode will rectify A.C. from the alternator to top up the battery.

It's important to use the correct wattage bulbs to balance the alternator output power with the load (or you'll the bulbs).

Not the best system for running electrics, you have only 28 Watts from this alternator.

There should be a description of the electrical system somewhere in the manual.

Hope this helps

Max

The wiring diagram will work if you follow it. Your headlight does not seem to be wired correctly. Start with the stator. You should have three wires. Also don't use the headlight as a ground. Run one additional ground wire wire (that is not the color of the other ones) from the headlight to the frame near/at where the battery is grounded and use that instead. What is nice about this system is that if the battery dies you can still run the bike. Good luck.

duck749 wrote:I have been trying to figure out the operation of the low/high headlight and the left hand switch. <snip>

First off, can you please confirm that this is what you switch looks like?



It works like this:

Key OUT, switch position 0:
Nothing.

Key OUT, switch position 1:
Parking lights front and back, green idiot light. No horn, no brake light.

Key IN, switch position 1:
Dipped headlight, rear light, brake light and green idiot light.

Key IN, switch position 2:
As above but now MAIN beam (dazzle, dazzle ...)

So it seem that it's just that your headlamp wiring that isn't working, either on dipped or main. Time to get the continuity tester out ...