ducatipaso.org

Hi Guys and maybe Girl.

I have just had a break down of the regulator unit, and I have replaced it with a RR51 type. My PASO alternator has 3 wires, 2 yellow and 1 red. The regulator has only 2 yellow ( and of course 1 red(bat +) 1 Green (bat - ) and 1 white for the dashboard light indicator). According to the instruction, when the alternator has 3 wires as the PASO has, the 2 yellow wires go the 1 yellow wire on the regulator, and the red wire from the alternator, is to go to the other yellow on the regulator. BUT THIS DOES NOT WORK !. But if I connect the alternator as if it only to the regulator with only the yellow lines connected Yellow to yellow it seems to work. The voltage shows 13 volt fully loaded.? You know, I am satisfied that it works, but it just tiks me that it doesn’t work according to the plan. Does any one have a explanation.

Regards
Klaus

The answer to your question depends on when your bike was made, and where it was sold. My '90 sport that was sold in California has three wires coming out of the alternator, but the red wire is unused. I don't know why. I hooked it up according to the wiring diagram I had, but I got no voltage. I taped it off, and got a good 14v. Much later I got a hold of the wiring diagram for this specific bike, and it had only the yellow wires attached.

What did your old regulator have?

Hi Nilaus
The two yellow wires are the main alternator coil connections. The very ends of the bit of wire that makes up the coil in the alternator. The red wire is a centre tap in the middle of the coil. If you connect the two yellow alternator wires together and then connect them to one of the yellow regulator wires, and the red centre tap to the other yellow reg wire, the power generated in each half of the coil cancels itself out. The power is dissipated in the alternator windings and the wiring loom, and if run for long enough may cause the coil to overheat and go open circuit - not easy to fix.

If you imagine the centre tap on the coil as the zero voltage point the extremities of the coil (yellow wires) alternate (ie an AC generator) between positive and negative, but are always the opposite of each other. (There is more than one physical coil in the alternator but the concept is correct as they are all connected together).

Connecting the yellow alternator wires to the yellow reg wires is fine. Leave the red alternator wire disconnected- tape it up and tie it down so it can't short to anything.
To check the story above you could connect one yellow alt wire to one yellow reg wire, and the red alt wire to the other yellow reg wire. This will also work but you will only have half the alternator power available at the regulator.

In fact, on the bit of paper that came with one of my replacement regs years ago, it says pretty much that. Also says in brackets that the other yellow alt wire is not used.

The coil theory is much the same as the secondary winding of a mains power transformer. Search on Full Wave Centre Tap or Full Wave Bridge Rectifiers for more info. Don't worry about the maths but see http://www.atc-frost.com/products/design/va.htm for some illustrations on how the coil connections work in concept. The regulator has the diodes inside - and plenty of other bits.

cheers
Dave

Hi,

Electrex have a new model now named ESR510 (formerly RR51), however in the instruction it says on the left:
"you will have a red wire left over. Make sure to cap it off ..."

http://www.electrosport.com/Images/fitting.esr510.a.pdf

G.

Thanks for all your answers, you have been most help an informative. My old regulator, which I was told was an original one, had 3 connections from the stator. But as I wrote before, it works.