Charge indicator/warning light assimilator function. 1973 850 Commando

Jonez69

Jonez69

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I'm refreshing my red 73' this winter. The only electrical component that does not function is the charge warning light. I tested the bulb and it is good. New 3 phase stator is sending 14 plus V to the battery. i haven't check continuity from the assimilator to the light itself. My question is, if indeed the assimilator unit is bad, will it give me problems down the road if I just leave it in place rather than replace it? Thanks for your replies!
 
Can't answer your exact question but many owners replace the assimilator with a charge warning LED light, such as from this bloke:

Improving Classic Motorcycles

Books and products to help you get the best from your classic motorcycle on today's roads
www.improvingclassicmotorcycles.com www.improvingclassicmotorcycles.com
These typically give more than just a yes or no response to charging, letting you know if under or over charging is happening. There are also some with an oil pressure low warning feature.
 
Jonez69 said:
I'm refreshing my red 73' this winter. The only electrical component that does not function is the charge warning light. I tested the bulb and it is good. New 3 phase stator is sending 14 plus V to the battery. i haven't check continuity from the assimilator to the light itself. My question is, if indeed the assimilator unit is bad, will it give me problems down the road if I just leave it in place rather than replace it? Thanks for your replies!
Click to expand...
Just leave it out - it will hurt nothing. And:

1) Connect the White/Brown wire currently connected to it to an oil pressure switch - low pressure - light on.
2) Install an actual battery monitor as @Tornado said.
3) Do nothing

BTW, the assimilator does not indicate battery charging. It only says that the stator is making AC power. Indicates nothing about the rectifier, Zener, or battery. And, they generally don't work at all with modern charging rectifier/regulators such as Podtrinics or Tri-Spark. Since you have a three-phase stator and a pre-MKIII I assume you don't have the original bridge/Zener.
 
The assimilator, as far as I know, is identical to the Lucas 3AW used on old British classic cars.
I have take apart a Lucas 3AW to try repair it.

It operates on a simple principle. It is a temperature operated relay. As voltage is applied, a bimetallic strip is heated that eventually moves and breaks the normally closed contact. The normally closed contact keeps the ignition warning light on.

If the assimilator innards are the same as a Lucas 3AW, then there is no harm to leave it as is. ie not working.
 
marshg246 said:
Just leave it out - it will hurt nothing. And:

1) Connect the White/Brown wire currently connected to it to an oil pressure switch - low pressure - light on.
2) Install an actual battery monitor as @Tornado said.
3) Do nothing

BTW, the assimilator does not indicate battery charging. It only says that the stator is making AC power. Indicates nothing about the rectifier, Zener, or battery. And, they generally don't work at all with modern charging rectifier/regulators such as Podtrinics or Tri-Spark. Since you have a three-phase stator and a pre-MKIII I assume you don't have the original bridge/Zener.
Click to expand...
Thanks, Greg and all
the warning light did not work when I bought the bike, so i just wanted to make sure it wasn't somehow tied to the system in a way that could leave me stranded. I had already learned of the battery monitor light as a replacement but was thinking of saving a bit of coin where I could, at least for now. Just this past month I have removed the zener and rectifier and installed a Tri-Spark MOSFET, along with the 3 phase stator. My old stator had seen better days. Also installed a Tri-Spark ignition and new Premier carbs. This bike is really solid and just needed TLC and new spares to replace tired and worn out bits.
 
Jonez69 said:
Thanks, Greg and all
the warning light did not work when I bought the bike, so i just wanted to make sure it wasn't somehow tied to the system in a way that could leave me stranded. I had already learned of the battery monitor light as a replacement but was thinking of saving a bit of coin where I could, at least for now. Just this past month I have removed the zener and rectifier and installed a Tri-Spark MOSFET, along with the 3 phase stator. My old stator had seen better days. Also installed a Tri-Spark ignition and new Premier carbs. This bike is really solid and just needed TLC and new spares to replace tired and worn out bits.
Click to expand...
So you've spent loads on all those nice bits...the charge warning LED's are less than 40 or 50 USD shipped from the UK (assuming you order before tariffs are brought into affect by your dear leader ;) ). There is a US made one as well if I recall.
 
Tornado said:
So you've spent loads on all those nice bits...the charge warning LED's are less than 40 or 50 USD shipped from the UK (assuming you order before tariffs are brought into affect by your dear leader ;) ). There is a US made one as well if I recall.
Click to expand...
:D Yeah, well I guess it isn't so much about the money to repair a warning light that tells me my brand new stator has output, as it is because I really don't feel like taking off the gas tank again to fix a semi-useless warning light since it doesn't make a hill of beans difference to the operating of the charging system. I have this bike ready to go on a shakedown when the weather cooperates. Temps reaching 50F next week!
 
My assimilator does work but I like to know the voltage so I bought something
like the below 12volt digital meter (see link) and siliconed it on top of the fork lock keyhole as it is small

Connections were easy as I connected one lead to the coil hot wire spade connector and one to a ground.

But its a rabbit hole.
I also installed an oil pressure gauge from Norton Holland Works. Great quality oil line from head to gauge.
Who knows, maybe one day an oil temp gauge or and oil cooler!

Dennis
 
Sometimes the assimilator can be easily fixed.

If it is high mileage and the contact is closed, there is corrosion/arcing buildup on the contacts and a simple filing works with a very thin blade file like a points file

But if the contacts are open, to me it is unrepairable.
Dennis
 
I have the ICM unit that is the one with the oil pressure added on with the sender unit from Don Pender that has been flawless for over 5 years now.Not an expensive piece. I like the way it shows me when the ignition is on and then goes off when bike is running.Hides in the headlight shell nicely.
Mike
 

ICMotorcycles.com &nbsp Ignition / Alternator / Battery / Charge Warning Lights

Ignition Alternator Battery Warning lights Charge monitors. Combined charge and oil pressure warning lights
www.improvingclassicmotorcycles.com www.improvingclassicmotorcycles.com
Tornado said:
Can't answer your exact question but many owners replace the assimilator with a charge warning LED light, such as from this bloke:

Improving Classic Motorcycles

Books and products to help you get the best from your classic motorcycle on today's roads
www.improvingclassicmotorcycles.com www.improvingclassicmotorcycles.com
These typically give more than just a yes or no response to charging, letting you know if under or over charging is happening. There are also some with an oil pressure low warning feature.
Click to expand...
 
Had a somewhat similar issue a couple of years ago with the charging system on my 1974 850 MKII Commando. While I never found a definitive answer, the general trend of advice was that a three phase alternator is incompatible with a standard "warning light assimilator". I binned my "warning light assimilator" and following advice from this forum, (and as suggested above) installed a "charge warning light" from:

Improving Classic Motorcycles

Books and products to help you get the best from your classic motorcycle on today's roads
www.improvingclassicmotorcycles.com www.improvingclassicmotorcycles.com

Works great! Is much more useful than the "warning light assimilator", in that it monitors the state of the battery and not just whether the stator is producing current or not. Worthwhile upgrade!
 

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