General => Douglas Motorcycles - General Discussion => Topic started by: Sgtbiro on 20 Nov 2020 at 18:13

Title: More electric questions
Post by: Sgtbiro on 20 Nov 2020 at 18:13
Hi Still trying to get my head round putting my new harness onto my Dragonfly. My next puzzle is i am fitting a solid state rectifier and i don't know where to put the wires from the harness.
I think the brown wire is the AC  coming in from the generator.
The blue wire is the DC going out to the lights .
But i don't know what the red wire is for and not sure what terminals they all go to on the rectifier see attached photo.
Can anyone advise please. 

Cheers Kevin.
Title: Re: More electric questions
Post by: EW-Ron on 20 Nov 2020 at 20:59
A bridge rectifier normally has 2 connections from the ac, and a +ve and -ve output.
If you didn't get any wiring instructions with this newfangled gadget,
you'll just have to plug it in and see what comes out where !
Is that the + and - marked on your gadget there ?

Now, you mention a brown wire from the 'generator'.
My memory is a bit mushy on what you have - year/model - does it in fact have an ac alternator ?
If you only have one ac output wire, it'll only have half wave rectification ?

At less than $2 each (in bulk), its cheap to experiment ... (
Title: Re: More electric questions
Post by: eddie on 21 Nov 2020 at 07:43
           Assuming you are retaining the 6 volt positive earth system, refer to the original wiring diagram and wire the 4 terminals of the solid state rectifier as follows:  + to earth,  -  to 6 on the switch (blue wire on original diagram),  AC to alternator (brown wire), AC to 3 on the switch (red wire).

  I think I saw in one of your previous postings that you are going over to 12 volt. If this is the case, other alterations to the wiring will be needed. Wire up the rectifier as before but omit the red wire. Join together the yellow and green wires from the alternator and connect them to the vacated AC terminal on the rectifier. This will now give you full output from the alternator irrespective of the switch position. You now need to wire a Zener diode between the negative terminal on the rectifier and earth (make sure you get the correct Zener diode (positive earth) - this will then control the charging voltage and prevent the battery from boiling dry. The Zener diode will need to be mounted on a heat sink as it can get very hot when dealing with the full current being generated by the alternator.

Title: Re: More electric questions
Post by: isettaman on 21 Nov 2020 at 08:55
Hi Kevin
Could I suggest a simple way to establish which wire goes where?
I always do this faced with a new harness. Get your multimeter and set it to resistance or Ohms and then work systematically through each wire to find where you get a circuit then you know which wire goes where, where it comes from and where it goes. Of course, label each wire as you go. You can also use a battery, wire and bulb to test for a circuit in the same way. Bulb lights up when connected to either end of a wire then you know where it goes.
Hope that makes sense.
Title: Re: More electric questions
Post by: Ken Rogers on 22 Nov 2020 at 09:11
Hi the photo is showing the positive connection and one of the 2 ac connection which are both on the left hand side