BTH Cut-Out

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
Michel
I found the wiring diagram which is a mixture of several different diagrams to work for the Miller / BTH combination.
For anybody else looking this is for a 1936-37 series A single that the factory fitted with Miller lights and a BTH mag generator. There was probably approx 50-100 bikes fitted with this combination.
BTH-Miller combined diagram.jpg
Simon
 

Michel

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VOC Member
Dear Simon,
Great, wonderful, beautiful ! Could you send it to me on my email address. I send it to you in PM. Do you come to the international rally in Belgium in 2019 ? If so, you will be entitled to one or more abbey beers if you like Belgian beers. I wish you an excellent weekend under the sun and driving your Vincent, of course :)
 

Michel

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VOC Member
Dear Simon,
I followed your diagram and the electrical circuits worked perfectly. But you have to install a connection between the terminals n°5 and n°7. In the next few days, I install the BTH cutout but I already noticed that the BTH generator charges (very) weakly.
Thank you.
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
Michel
You should not need a connection between terminals 5 & 7. If you do then there is something different with your headlight switch. The speedo bulb and rear light bulb should be on a separate terminal to the pilot bulb and the switch connects them up depending on the switch position. Here is what each switch position should do on a series A single with Miller lights:

Off - no lights and no charging.
Ch - no lights and the battery charges through the charge resistor at a low rate.
Hi - Main headlight on, speedo bulb on, rear light on and charges full rate (resistor not been used). Note the pilot bulb is not connected or used in this position.
Lo - Speedo bulb, back light and pilot bulb connected. Note the main headlight is not connected in this position.

The above switch positions work exactly the same on series B & C bikes but as they have charging regulator on the dynamo and not a charging resistor then position 2 does nothing.

Simon
 

Michel

Well Known and Active Forum User
VOC Member
Simon, we agree.
Next step, replace the manual switch with the BTH cut-out.
Wait and see, as our English friends say.
Michel.
 

Michel

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VOC Member
Hi everybody,
And that's it, the cut-out is in place and everything is working normally. Except that the cut-out has not closed yet because the battery is fully charged.
 

Michel

Well Known and Active Forum User
VOC Member
Hello Simon,
Considering the BTH generator, what is the capacity (Ampere / hour) of the battery 6 volts lead on your Comet and you advise ?
Michel.
 
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