Assimlator question when changing to negative ground

To resolve the turn signal and headlight LED issues on my 74 Commando, I have gone with the Podtronics unit and have converted to Negative ground/earth. (Removed rectifier assembly and Zener).

I had never noticed the assimilator before. Mine is the three-post version, and by the info on the NOC site, it is a mechanical device. My question is: Is it sensitive to polarity? Do I need to re-wire it or replace with a modern device? I searched the accessnorton site, and found some information but still need this question answered.

NOC link:
https://www.nortonownersclub.org/support/technical-support-electrical/warning-light-assimilators

Thanks.
~998cc

Yes it is polarity sensitive.

Either swap it for a negative ground unit https://www.coolcatcorp.com/product/SS3AW.html

Or get a charge warning light, which in my opinion gives you far more useful information https://www.improvingclassicmotorcycles.com/products.htm


Your other alternative is to leave everything positive ground, and fit LEDs that are wired for positive ground bikes http://www.norbsa02.freeuk.com/goffyWhyNotLEDs.htm

This option makes it much easier for you (and others) to troubleshoot in the future, as all the wiring diagrams out there are correct, and all the red wires that go to ground won’t be so confusing!!!

gtiller said:

Your other alternative is to leave everything positive ground, and fit LEDs that are wired for positive ground bikes http://www.norbsa02.freeuk.com/goffyWhyNotLEDs.htm

This option makes it much easier for you (and others) to troubleshoot in the future, as all the wiring diagrams out there are correct, and all the red wires that go to ground won’t be so confusing!!!

Click to expand...

I agree with the portion I quoted of gtiller's post. IMO, converting to neg ground solves another one of those non-existent problems that is easier and more conveniently left 'unsolved.'

The stock assimilator is just a relay. I believe the coil works off AC from the alternator. Why would that be polarity sensitive?

maylar said:

The stock assimilator is just a relay. I believe the coil works off AC from the alternator. Why would that be polarity sensitive?

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Reasonably close but not an electromagnetic relay....It is a nichrome wire coil heater element around a bimetalic strip with a contact that opens when heated by approximately 6.5 VAC average (only 1 leg from the alternator) the opening contact is what ungrounds the red bulb
Not polarity sensitive...

dynodave said:

Reasonably close but not an electromagnetic relay....It is a nichrome wire coil heater element around a bimetalic strip with a contact that opens when heated by approximately 6.5 VAC average (only 1 leg from the alternator) the opening contact is what ungrounds the red bulb
Not polarity sensitive...

Click to expand...

+1
And IMHO it seems to use a ridiculous amount of power to keep a light bulb off. I use a coolcat solid state unit that gtiller suggests. Been on my bike for over 5 years and works fine.
Pete

In reality, after another quick look, part of the nichrome wire stretches while self heated, with a nichrome series limiter coil, and allows switch arm to swing controlling the red lights switch contact. delete bimetalic arm...

MexicoMike said:

I agree with the portion I quoted of gtiller's post. IMO, converting to neg ground solves another one of those non-existent problems that is easier and more conveniently left 'unsolved.'

Click to expand...

Good day MexicoMike.
Changing polarity of a Norton (or any automotive) electrical system has proponents and detractors, and I fully respect all points of view since all have merit in their own right.

Changing over to negative ground was a decision made over time, and it was a decision that was not made lightly. It came down to a few factors: 1. Maintenance and the availability of components at the local auto store; these components requiring negative ground. 2. I am used to negative ground systems on my bikes, cars, and radio projects. All being the same polarity lessens the odds of making errors when working on the systems or even attaching a battery charger. To minimize confusion, I also changed the colors of the Norton battery leads using heat shrink tubing.

The zener diode regulation method stresses the charging system components, so I wanted to change over to the Podtronics regulator; this provided the opportunity to switch polarity.

Regards,
~998cc

998cc said:

To resolve the turn signal and headlight LED issues on my 74 Commando, I have gone with the Podtronics unit and have converted to Negative ground/earth. (Removed rectifier assembly and Zener).

I had never noticed the assimilator before. Mine is the three-post version, and by the info on the NOC site, it is a mechanical device. My question is: Is it sensitive to polarity? Do I need to re-wire it or replace with a modern device? I searched the accessnorton site, and found some information but still need this question answered.

NOC link:
https://www.nortonownersclub.org/support/technical-support-electrical/warning-light-assimilators

Thanks.
~998cc

Click to expand...

Personally, I throw the silly thing away and install a oil pressure switch. I'm much more interested in knowing that I have oil pressure than knowing that the stator is making power. Madass140 sells a kit and I have his kits for those in the US.

I changed to negative earth once as the alarm I fitted would not work with a positive earth. The alarm failed so I quickly went back to positive earth. Just not worth all the hassle trying to remember how you rewired it and never being able to use the proper wiring diagram when fault finding. I am fully LED, the tail lamp is the only one that needs a dedicated solution to suit positive earth, all the rest are easy, the headlamp bulbs all seem to be ambidextrous out of the box and multi voltage.

I switched to negative earth when I changed voltage regulators and ignition, mostly to accommodate LED blinkers. Yes it sucks remembering that red is still ground and is now negative.

maylar said:

I switched to negative earth when I changed voltage regulators and ignition, mostly to accommodate LED blinkers. Yes it sucks remembering that red is still ground and is now negative.

Click to expand...

Red negatives can be a bit confusing, but for me, negative ground/earth is more natural.

Just finished testing the circuits. All four of the blinkers flashed at the same time. Traced this to the indicator lamp in the headlight shell bleeding current back through the inactive flashers. All good now but with no indicator for the time being.

~998cc

998cc said:

Red negatives can be a bit confusing, but for me, negative ground/earth is more natural.

Just finished testing the circuits. All four of the blinkers flashed at the same time. Traced this to the indicator lamp in the headlight shell bleeding current back through the inactive flashers. All good now but with no indicator for the time being.

~998cc

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Yeah it's a clever scheme that they used that works with bulbs but not with LEDs. The current for the flasher indicator light runs through the non-blinking bulbs. I fixed that by isolating the indicator with a couple diodes.

maylar said:

Yeah it's a clever scheme that they used that works with bulbs but not with LEDs. The current for the flasher indicator light runs through the non-blinking bulbs. I fixed that by isolating the indicator with a couple diodes.

Click to expand...

Thanks Dave.
Diodes are great devices; this world would be a very different place without the physics of semiconductors. That's a good solution, and I plan to isolate the indicator lamp with a common ground and diodes as well.

Regards,
~998cc

dynodave said:

In reality, after another quick look, part of the nichrome wire stretches while self heated, with a nichrome series limiter coil, and allows switch arm to swing controlling the red lights switch contact. delete bimetalic arm...

Click to expand...

Dynodave, Good information. One would think that in the mid-70's a solid state device could have been incorporated...? Solid state regulators were provided in some 60's American cars; the indicator power could have been picked up there. I did see that the assimilators were used in cars as well, so perhaps the device was too well established to reinvent as solid state. For whatever reason, mine stopped functioning after the conversion to neg ground.

Regards,
~998cc