Warning Light Gremlins

Not open for further replies.

Ron Hulton

Jul 18, 2005
Country flag
So what else is new on a Norton ?? Just installed a Sparx 3 phase high output kit on my MkIII . In order to get the red warning light to go off i had to tie into two of the three yellow wires from the regulator and terminate them to the two " AL " positions on the warning assimilator switch .

This is where the fun starts ..

Key on , red light on

Start the engine and the red light goes out just like it should.

As the revs increase the red light comes back on . Not noticeable during the daytime but at night you'd think it was Rudolphs nose . I realize that RGM makes a unit that fits in the headlight shell but that is not telling me what or why this is happening . Has anyone successfully done the Sparx mod using the old assimilator switch and if so , what am i missing.

Thanks in advance

Hmm... Millard has the solid state assimilator wired as you and claims his works fine. I don't have a three phase on my MkIII, but do on my '73 850 Interstate, but it had the earlier mechanical (can-type) assimilator with only one alternator connection. I could not make it work, so went with the voltage sensor from RGM.

From Al Osborne on the solid state assimilator:
"The voltage applied from the ignition terminal biases the transistor on, and the warning lamp lights.

As soon as there is an output of sufficient voltage from the alternator the transistor is biased off and the warning lamp goes out.

Again the system is not that clever when it comes to failures elsewhere and the transistor is very vulnerable from any overloads."

Could it be that as the revs increase, the three legs of the alternator passing rectified voltage through the ignition switch terminal is too much for the two legs you have connected (supplying un-rectified AC voltage) thus overpowering the transistor?

I may be talking out my A$$ here as I am no electronics expert. As I say, Millard reports his is wired as yours and works. Perhaps your assimilator is faulty?

Here is a link to Al Oz's explanation:

Hiya Ron
As Ron L says, mine is wired that way and works fine.
Sorry I can't offer any words of wisdom though as electricks is a bloody mystery to me akin to black magic.
I did find the guy at Tri-cor helpfull though when I called for wiring instructions - before I noticed them on their website :?
Maybe give em a call?
(+44) 01432 820 752

I think the can-type assimilator is incompatible with three-phase. I don't understand the electrics of it so can't offer a lucid explanation unfortunately!!! I had a three-phase alternator on my 74 Commando for awhile and the warning light was always on. Switched to a high output single phase alternator and it seems to work fine. You are probably better off switching to some sort of solid state warning system anyways. I have heard a few folks say the old can-type are subject to vibration damage and aren't very reliable.
I may be way off the mark here, and it doesn't help that i don't have the wiring diagram in front of me, but i have an idea of what it might be. I also apologize in advance if what follows is a real long explanation of something that's common knowledge to everyone else...
At the risk of sounding too obvious, the regulator... er, regulates the voltage going through the system by comparing the input voltage to some internal benchmark voltage. (Note that if you're still using the zener diode, that acts as your regulator) If it determines the voltage coming through from the alternator is a "healthy" voltage it allows it through to charge the battery, as well as going to the assimilator which then sees appropriate voltage and, therefore, a properly-operating alternator.
However, if the voltage is too high it does either one of two things, depending on the regulator type. It can either short SOME of the current to ground to bring the voltage down to an acceptable level that won't toast the battery and various electrical bits living on the system, or it'll just act like a regular switch and short ALL current to ground until the input voltage drops back down to a reasonable level.
With your steroided hi-output charging system, i'm guessing that at low revs and when idling the system charges fine and the warning light stays off, but your revs don't have to go up too high before that high voltage threshold on the regulator is met and it starts shorting everything to ground. I'm also guessing the series goes alternator to reg/rec to assimilator to warning light, and in that case the assimilator won't see any voltage coming from the alternator since the regulator's shorting it all to ground. Then the light goes on because the assimilator thinks the alternator's dead, when it's actually just working TOO well and the regulator is stepping in to protect the battery from getting fried.
Of course, this is all assuming the regulator on your bike is one that dumps everything to ground once the upper voltage limit is met, or dumps enough that the voltage going to the assimilator is low enough to set off the warning light. It's also assuming the assimilator is just connected to the regulator and not tied into the alternator somehow and directly reading its output. I think both of these depend on whether you have a newer reg/rec setup like Podtronics or the old Lucas rectifier and zener setup because they're wired up slightly different. This is my basic understanding of this stuff applied to just the Commando, so somebody let me know if Commando/Lucas components act differently than this. They ARE Lucas components after all...

Not that this helps fix the problem or anything either, but if i'm right at least you'd know when the light comes on at higher revs that it's not because the alternator's going bad...
Scheffy.G said:
It's also assuming the assimilator is just connected to the regulator and not tied into the alternator somehow and directly reading its output.

Well...actually, the assimilator is triggered directly by the generator AC output, it being connected to one (in the case of the silver can type) or both (850 MkIII encapsulated type) stator wires.

I must admit to being a bit puzzled why Millard's setup works and Ron's doesn't but there could be a difference between the two systems that nobody is aware of?

Here is the layout of the two different types of assimilator:

http://www.nortonownersclub.org/technic ... etail.html

(actually there are two types of encapsulated MkIII assimilator as Canadian models had an assimilator that switched the headlamp on after the engine had started)

Here is the electrical section from the 1970-72 workshop manual which has the (up to '72) wiring diagrams included, but not the late types (like MkIII):

http://rocbo.lautre.net/technique/norto ... p/135.html

Use the: << < > symbols to change the page.
O.K. Here's the story. At 600 rpm the red light is on just like it is supposed to be . As the rpm is increased to 1000 the voltage rises to approximately 13 volts measured at the light itself. As the RPM is further increased the voltage drops and by 2000 rpm the voltage now reads 11.2 v and the light begins to flicker. Any further increase in throttle will decrease the voltage even more and the light becomes a steady red.

Now the other half of the story is ............ using my digital meter to check voltage at the battery the voltage increases/decreases normally as the throttle is increased/decreased. It would appear as if something is happening at the assimulator switch itself ............ but what ????????? The switch is the flat type .. PN 06-6393
Ron, you trying to get ready for mid-Ohio again? You still have all your juice going through the kill switch?
Mid Ohio ??? gosh , last time i went there it was nothing but grief but i'm always up for a ride . Is there something on i should know about ??

Power still through the kill switch . Ya !! as far as i know . I haven't changed anything ( that i can remember)..
Not open for further replies.