Assimilator question

I'm in the debugging phase of my 72 Roadster project.
The warning light on the headlight body does not light when I turn on ignition, prior to starting or when running.
I've confirmed bulb is good and white wire coming to lamp is hot when ignition on.
I've checked connections on brown/wire back to the assimilator and if I ground it the light comes on as it should.
However when connected to the WL at the assimilator the light does not come on which sounds like problem within assimilator.
However both my old original assimilator and my new one have same problem so I'm thinking assimilator ok.

Assimilator wiring is white/brown to WL, green/yellow to AL and red to E.
I followed the troubleshooting instructions in my workshop manual for assimilator which called for swapping the white/brown from the "WL" terminal to the "E" terminal. If assimilator was bad the bulb should light, which it didn't.
In that case it says the problem would be wiring, which I've checked every way I can think of.

The green yellow comes from the alternator by way of the rectifier but from what I know about electrical I doubt that is the source of the problem.

Any suggestions would be appreciated.

Thanks
Bob

rx7171 said:

I've checked connections on brown/wire back to the assimilator and if I ground it the light comes on as it should.

Click to expand...

Did you try connecting the brown/white wire directly to the red assimilator wire? If you did that, and the bulb lit up, then the assimilator must be faulty? If the bulb still didn't light, then the fault must lie somewhere along the red wire, so try connecting a jumper wire from assimilator 'E' to ground, and see if the bulb lights?

Bob

I'm not sure from your description how your green/yellow AL feed is wired, but I believe the assimilator actuates from AC rather than DC input--and the AC input need not be high--my light goes out during kick-starting. The ground is interrupted to extinguish the light--double grounding doesn't hurt. You might try running a jumper direct from the alternator green/yellow wire to the AL terminal.

It is a frustrating exercise sometimes to get these things to work. Good luck



Tim Kraakevik
kraakevik@voyager.net
'72 Combat

kraakevik@voyagernet said:

You might try running a jumper direct from the alternator green/yellow wire to the AL terminal.

Click to expand...

I don't quite see how the AC output could be the cause of this problem?
As AC output triggers the assimilator to turn the warning lamp OFF by interrupting its circuit once the engine reaches a certain RPM, but in Bob's case the warning light doesn't actually come ON to start with?

The only other thing I can think of, would be if a rectifier diode has failed and is passing current, then battery current could be leaking to the assimilator unit and may possibly be causing it to trigger?
This is only a guess, so I suggest Bob that checks what happens when the green/yellow wire is disconnected from the assimilator (with brown/white and red connected to their assimilator terminals)?
If the warning lamp then lights up, the problem could be the rectifier?

I don't know that it is worth mentioning but I solved a host of wiring issues by throwing away the original connector block under the fuel tank and connecting wires directly. I was chasing a number of problems that magically fixed themselves when I took this step. The block looked fine on inspection but the internal metal butt connectors had started to fail. I would be suspicious of any original connectors regardless of where they are located or or how they look.

Thanks everyone for your suggestions.

The one that I tried first and worked was L.A.B.'s

Did you try connecting the brown/white wire directly to the red assimilator wire? If you did that, and the bulb lit up, then the assimilator must be faulty? If the bulb still didn't light, then the fault must lie somewhere along the red wire, so try connecting a jumper wire from assimilator 'E' to ground, and see if the bulb lights?[/quote]

Once I brought in a new ground to "E" it works.
Rather than chase the wiring harness ground it was simpler to just create a new ground directly to the frame to "E".

Now light comes on when I turn on key and quickly goes out when I start the bike, confirming my alternator is working. Cool.

Thanks
Bob