There are only three wires
 

So how could I stuff it up, right?
This is a schematic for the Denso alternator, R1100S Model 1999.
I can't get the alternator to charge. Is there a multimeter test to check the 'IC". What should I see?
http://forums.pelicanparts.com/uploa...1224446792.jpg

If you have a volt meter you can measure the alternator output. It ought to be somewhere in the neighborhood of 14 V, measured across the red & yellow wires in your schematic.

I take comfort...
 

...that at least 67 others didn't know.
The trigger wire is the one that runs through the idiot light. ?!? Thats just dumb - if the idiot light burns out (blue to yellow/green), not only will the charging system not work, you wouldn't know about it before the battery went flat. And once the battery went flat, would anyone think to check that the globe was burnt out before going through the effort of checking the alternator???

http://forums.pelicanparts.com/uploa...1224469714.jpg

Whats the voltage at the battery terminals with the bike running? how about at 3k rpm?

I got it figured out finally!

Before, with the ignition off, the battery voltage was 12.8 v
With the ignition on, fuel pump off, system voltage dropped to 12.4 v
With the engine running, fuel pump on, system voltage dropped to 12.2 v
With the engine running and the trigger wire properly connected, i.e. to the idiot light circuit, system voltage is a strong 13.8 v.

Cool!

Still blown away by how the circuit is designed though.

That has been the standard for YEARS, at least for the European auto industry. NO charge, FIRST thing to check is whether the light illuminates when the key is first turned on. If it does not, take your handy-dandy 12 v test light, connect the clip to the positive battery terminal and touch the terminal, if it charges, you found the problem.

Well, obviously it is a valid design then. But what is the other wire for? (the green one?)

I believe that is the one the regulator monitors for system voltage, to regulate the charging rate.

That makes sense. Thanks!

That has got to be one of the silliest designs I have seen. I simple lamp failure brings down the charging system, what on earth where they thinking?
Designed in unreliability, just what everyone needs.

Clear something up for me here...
Looking at the diagram, the blue wire is just a switched 0v - when the alternator output is good the IC lets the blue wire float so's the lamp does not light - at other times the IC drops the blue wire to 0v.
The green wire is +12v for the IC
What is this 'trigger' function of the blue wire?
many thanks

It is a bit of a mystery to me as well, but the electrician I took it to said that the alternator will only produce current if the warning lamp circuit is complete. If there is no 12VDC to D+ (hard to see on the scan but that is the name of the circuit with the blue wire), then the alternator does nothing but spin. Go figure.

Please don't get stuck on the terminology...trigger is my interpretation of function; the en-gah-nears probably used several words with a total of twelve syllables to describe it.

Being an alternator and not a "classic" generator it uses an electromagnetic current to produce the magnetism, where the classic generator used a permanent magnet.

That being said the design uses the small current through the bulb to produce a small amount of magnetism to get the process started. Once there is power output from the alternator the regulator feeds that back into the field circuit, thus removing the load through the bulb and shutting the light off. Actually quite simple and common.

BTW, that is why the alternator light stays on sometimes if you don't add revs after it is started. The weak magnetic field does not let the process get started, but after a few revs are added and the process gets started, they will still charge at idle. Conversely, if the lamp blows, as in this case, there is sometimes enough residual magnetism in the rotor to start the process if you add a lot of revs. So if ever stranded with no bulb to fix it, just wind it up to redline once and you may get the alternator charging to get you home.

that's a really really useful reply, thankyou. Much better than the lunatic drivel that's taken over that other thread about tyres, ahem.