Ron L
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- Feb 27, 2004
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Since the forum has been a little slow lately, I'm going to try to describe what I have learned and have yet to learn about the Lucas 35601 stop switch. Over the years I have collected a handful of new and used 35601A switches and read everything I could about them. Most of the information is from Triumph and BSA sources as I found little information from Norton or Lucas. Unfortunately, much of what I found has been proven incorrect by my testing of the switches I have in my collection.
1) "There are two different 35601A switches differentiated by a black or brown button. " This appears to be substantiated by a Triumph service bulletin from January 1966. It states that the brown button models are suitable for battery and coil ignition motorcycles while the black button models are only suitable for AC energy transfer ignition. What could be the difference? Well looking at the ET wiring diagrams vs. the battery and coil (P11), we see the kill button on the ET ignition simply connects the points leads together.
The kill button on the battery and coil ignition (on a P11) takes both the points to ground at the handlebar.
So the switch for battery and coil version will show continuity from each connection to the metal switch body when the button is depressed. The version for the ET ignition only shows continuity between the two terminals when the button is depressed and not between either terminal and the metal body.
Sounds good. Brown button for battery and coil and black button for ET. Maybe this was true back in 1966, but the half dozen or so buttons I have are a mixture of black and brown and all will ground through the housing. Hmmm... Maybe manufacturing was changed after 1966. Certainly the ground through the housing button will work for ET ignitions as well, so why make two versions.
2) The 31071 button does not ground to the housing when depressed. That is my experience when I test the one example I have. Perhaps Lucas changed the number on the ET variant to 31071 at some point and discontinued using brown buttons on the battery and coil 35601?
3) If you are using an electronic ignition on your P11, to use either of these buttons you should install a relay. You want to open the circuit to the electronic box, not send it to ground. Set up the relay so it is normally closed on the ignition side and grounding the button will energize the relay coil.
4) The difference in the housing for this switch between Triumph and P11 has been documented before, but to reiterate, the Triumph is stamped steel while the P11 is machined and is thicker and has a square shoulder compared to the Triumph.
I hope this helps somebody, and if you have any different results, let us know.
1) "There are two different 35601A switches differentiated by a black or brown button. " This appears to be substantiated by a Triumph service bulletin from January 1966. It states that the brown button models are suitable for battery and coil ignition motorcycles while the black button models are only suitable for AC energy transfer ignition. What could be the difference? Well looking at the ET wiring diagrams vs. the battery and coil (P11), we see the kill button on the ET ignition simply connects the points leads together.
The kill button on the battery and coil ignition (on a P11) takes both the points to ground at the handlebar.
So the switch for battery and coil version will show continuity from each connection to the metal switch body when the button is depressed. The version for the ET ignition only shows continuity between the two terminals when the button is depressed and not between either terminal and the metal body.
Sounds good. Brown button for battery and coil and black button for ET. Maybe this was true back in 1966, but the half dozen or so buttons I have are a mixture of black and brown and all will ground through the housing. Hmmm... Maybe manufacturing was changed after 1966. Certainly the ground through the housing button will work for ET ignitions as well, so why make two versions.
2) The 31071 button does not ground to the housing when depressed. That is my experience when I test the one example I have. Perhaps Lucas changed the number on the ET variant to 31071 at some point and discontinued using brown buttons on the battery and coil 35601?
3) If you are using an electronic ignition on your P11, to use either of these buttons you should install a relay. You want to open the circuit to the electronic box, not send it to ground. Set up the relay so it is normally closed on the ignition side and grounding the button will energize the relay coil.
4) The difference in the housing for this switch between Triumph and P11 has been documented before, but to reiterate, the Triumph is stamped steel while the P11 is machined and is thicker and has a square shoulder compared to the Triumph.
I hope this helps somebody, and if you have any different results, let us know.
