Thumbs up! Posted October 24, 2019 Report Share Posted October 24, 2019 Hey Guy's,I have a 138 I have been sorting out and I am not sure if I have the correct brake light switch? When I apply the brake pedal it extends the switch pin and opens the circuit so when your foot it not on the brake pedal the switch is compressed and the circuit is closed,does that make sense? Quote Link to comment Share on other sites More sharing options...
johnjsy Posted October 25, 2019 Report Share Posted October 25, 2019 Hi, it seems to be the wrong switch. With the pin in it should be open circuit, pressing the brake pedal allows the pin out, completing the circuit, the brake light works. What is needed is a reverse light switch as used on pretty much any car. If you have a decent auto parts store near you, call in and see if you can find a suitable one. Take a multimeter with you, set to the diode range, be sure the contacts close when the pin is out. Hope this helps........ Quote Link to comment Share on other sites More sharing options...
lorenzo Posted October 25, 2019 Report Share Posted October 25, 2019 Hi , Thumbs Up - If your Alpina is wired as per original direct lighting , the stop lamp circuit is via the "earth/ground " side of the ignition feed coil in the magneto. Quote from an earlier posting on the subject:- . The switch is of an unusal design and exact replacments can not be found. The original switch is held in a normaly closed condition by a tag on the brake pedal and switches to normaly open when the pedal is depressed. Ignore the previous response - you do have the correct switch. 1 Quote Link to comment Share on other sites More sharing options...
Thumbs up! Posted October 25, 2019 Author Report Share Posted October 25, 2019 (edited) 9 hours ago, johnjsy said: Hi, it seems to be the wrong switch. With the pin in it should be open circuit, pressing the brake pedal allows the pin out, completing the circuit, the brake light works. What is needed is a reverse light switch as used on pretty much any car. If you have a decent auto parts store near you, call in and see if you can find a suitable one. Take a multimeter with you, set to the diode range, be sure the contacts close when the pin is out. Hope this helps........ 8 hours ago, lorenzo said: Hi , Thumbs Up - If your Alpina is wired as per original direct lighting , the stop lamp circuit is via the "earth/ground " side of the ignition feed coil in the magneto. Quote from an earlier posting on the subject:- . The switch is of an unusal design and exact replacments can not be found. The original switch is held in a normaly closed condition by a tag on the brake pedal and switches to normaly open when the pedal is depressed. Ignore the previous response - you do have the correct switch. Thanks for the replies Guy's, I will have to find a image of the wiring diagram to wrap my head around this type of system. Lorenzo, does this switch look like it is an original OE switch that Bultaco would have used or a replacement,the switch had no continuity but after using some electrical spray cleaner it is working again. Edited October 25, 2019 by Thumbs up! Quote Link to comment Share on other sites More sharing options...
lorenzo Posted October 25, 2019 Report Share Posted October 25, 2019 Hi, Thumbs Up - I have no direct experience of model 138 and am making a few assumptions here,,,,,,my own Alpina is an earlier model. Looks to me like an OE switch, though. If it's direct (AC) lighting - no battery and no rectification - it should be wired similar to this :- Hope this helps. Quote Link to comment Share on other sites More sharing options...
Thumbs up! Posted October 26, 2019 Author Report Share Posted October 26, 2019 Hi Lorenzo, As I understand it AC is Alternating Current and DC is Direct Current.Yesterday I used an ohm meter and applied it to the yellow wire from the engine case and got current to the green wire at the taillight,then I connected the two wires at the brake light switch I got power at the black wire and green wire at the brake light. In my mind that tells me the tail light is on when the engine is running and the brake light is on also when the brake light switch is in the closed position (pin compressed and brake pedal not being applied). The tail lamp has been modified at some point and had a single filament bulb and socket in it,would this not supposed to be a dual filament bulb and socket originally? Quote Link to comment Share on other sites More sharing options...
Thumbs up! Posted October 26, 2019 Author Report Share Posted October 26, 2019 I found this simple diagram for the switch that confirms the switch is normally closed and uses a path with a resisitor when open.Does this connector look like the spot where the resistor would plug in? Also note this bike does have a battery compartment. Thanks in advance! Quote Link to comment Share on other sites More sharing options...
Vincentm Posted November 1, 2020 Report Share Posted November 1, 2020 Have you had any luck with a wiring diagram for the 138 ? I've just got one, an American import with a switch on the headlight and could always do with help on wiring. Quote Link to comment Share on other sites More sharing options...
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