warning light assimilator

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I think I've broken mine... Does anyone know if this thing breaks if you swap the cables? I think the alternator works, but how do I know when the red light keeps on? Is there any substitute for this thing that's more reliable?
Cheers!
 
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Sparkplug,

A rudimentary but quick check of your alternator output can be made with a volt/ohm meter. Simply set the meter to DC volts and attach the leads to the battery. Next rev up the engine and watch the meter – it should show a voltage increase from 12.5VDC at idle to about 13.5VDC at around 3,000 RPM. If your readings are close to these, chances are your alternator is OK.

Now, the red “assimilator” light will glow at idle and will not go out until the engine reaches some 1,300 RPM; if your light behaves in a similar manner, it’s working properly.

Jason
 

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solid state warning light assimilator

L.A.B.

Have you used one of the assimilators you showed? These were made for the higher ouput alternators on the 850Mk3 Commandos. They have one extra lead you need to deal with. I tried one on my '72 750. The warning light would not go out until around 3,000 rpms. I ended up going back to the aluminum can which are poorly made and overpriced. Unless you really need an idiot light, just unplug the thing and live without it.

Use a multimeter across the battery terminals with the engine revving to see if the alternator is working. You should get around 14Volts at full output.
 

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I didn't know that the Mk3 type do not work on earlier Commandos with the lower output alternator. I haven't used the AO type yet so cannot say if that type is any different but then I own an 850 Mk3.

The 'LVS' version offered by A O Services would seem to be the one to use on the earlier models: http://www.aoservices.co.uk/data/lvs.htm
 
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As a follow on to this thread my 850 Mk2A warning light recently started occassionally coming on. When riding along at various revs the warning light faded on and then went out again but it is now getting worse and won't go out. This problem started about a week ago - about 200 miles of riding.

Jason Curtiss said:
Sparkplug,

A rudimentary but quick check of your alternator output can be made with a volt/ohm meter. Simply set the meter to DC volts and attach the leads to the battery. Next rev up the engine and watch the meter – it should show a voltage increase from 12.5VDC at idle to about 13.5VDC at around 3,000 RPM. If your readings are close to these, chances are your alternator is OK.

Jason

Having read the above I've just checked my voltage at the battery - 12.5v with ignition on but engine not running and 11.8v with engine running. Engine revs or headlight on or off don't make a difference to this 11.8v reading.

The bike still has the original blue assimilator but this doesnt seem to be the problem as by checking the voltage straight from the battery the readings would not be affected by a duff assimiltor as this only regulates power to the warning light :?:

Also have also checked and cleaned the connections on the Zenner.

Anyone got any ideas :?: The charging side of electrics are not my strongest point :!:

I can't check the alternator output directly as my meter does not do AC :!:
 

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mike916sp said:
The bike still has the original blue assimilator

That's not the assimilator (unless somebody has painted it?) that is the 2MC emergency starting capacitor, check the wire colours as the 2MC wires will be brown/blue and red. The metal can type assimilator is normally silver and found under the tank (later Mk III type is rectangular black plastic fitted on the front of the battery tray) the 2MC capacitor is usually found at the rear of the battery. The assimilator wires are white/brown (from w/light) and green/yellow (from generator AC).



You could try disconnecting the alternator wires and connecting a headlamp bulb to them, then start the engine, the bulb should light up and get brighter as the engine is revved if there is output, but don't rev it too high though.
 
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Sorry about that - it is the original 2MC capacitor just behind the battery just getting bits mixed up. As I said these are the first charge problems I've had since buying the bike a year and a half ago and I'm not that familiar where all the bits are yet.

I've not tried a headlight bulb yet but just had another thought before I try it.

A few weeks ago I noticed that some of the wiring, which is all original, in good condition and not messed about with, got trapped between the headstock and the steering stop on the left hand side of the bike when on full lock. This resulted in a break in the wiring to the flasher warning light. I've since soldered up the breaks and shrink wrapped the joints which cured this problem.

Does any alternator output wiring run through this same area? My thought is that if some wiring in the alternator circuit was damaged as well as the indicator wiring when the wiring got pinched this might have cause my charging probems.

It seems odd thinking about it that the charge problem appeared at about the same time the wiring was getting trapped.

By the way all wires are now securely cable tiedell away from the steering stop.
 

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mike916sp said:
A few weeks ago I noticed that some of the wiring, which is all original, in good condition and not messed about with, got trapped between the headstock and the steering stop on the left hand side of the bike when on full lock. This resulted in a break in the wiring to the flasher warning light. I've since soldered up the breaks and shrink wrapped the joints which cured this problem.

Does any alternator output wiring run through this same area? My thought is that if some wiring in the alternator circuit was damaged as well as the indicator wiring when the wiring got pinched this might have cause my charging probems.

It seems odd thinking about it that the charge problem appeared at about the same time the wiring was getting trapped.

A damaged wire (white/brown) between the charge warning light and the assimilator could cause the w/light to malfunction if it was shorting, but no charge circuit wires should go through the headstock area.

Check all brown/blue wire connections, remove and clean the Zener and rectifier earth studs (don't do the nuts up too tightly when refitting them) try disconnecting the red wire from the 2MC unit briefly and see if that makes a difference to the voltage with the engine running, the Zener can also be tested by running the engine at low revs with it disconnected and checking if that increases the voltage, if so the Zener could be faulty?
 
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Sorted the problem.

Cleaned all the wiring and earth connectors including removing and cleaning zenner and rectifier - no difference. So one trip to Halfords later to buy a multimeter which did AC I found no output was being produced by the alternator.

Traced this to one of the two wires from the alternator which had some insulation broken away near the bullet connectors and had rubbed some loose broken strands through the insulation of the other wire from the alternator and was shorting out. This was all covered by the outer black plastic casing so was not visible.

Anyway cut the wiring back to the other side of the break, soldered on some new bullets and all is now fine :D
 
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