Where did main beam go? |
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Dave P.
Senior Member Joined: 12 Jan 2015 Location: Northants Status: Offline Points: 5573 |
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Posted: 28 Jun 2020 at 16:28 |
I spent most of yesterday afternoon trying to answer the above question.
The V7 Special(1971) had suddenly lost main beam, and having just fitted a new dip switch I thought I'd done something wrong. The circuitry is made more complicated as it all goes via relays and two auxiliary headlamps are also included in the plot. I checked the wiring for bad connections etc and having completely rewired the bike last year I thought that I'd messed up.The culprit was eventually found; one of the Lucar male terminals on the changeover relay was ever so slightly, almost imperceptibly loose. Just the lightest touch would bring the main beam on then it would go off again when I removed my finger. This relay is maybe a year old,You can't win can you? |
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
1971 V7 Special. 1972 850GT. 1970 T120 Bonnie. 2009 500 Bullet. |
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ranton_rambler
Senior Member Joined: 13 Feb 2015 Location: Stafford Status: Offline Points: 1147 |
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I had to push start my SP last weekend. Same root cause - female connector not making good contact at rectifier. The particular terminal is the one that provides the field current to the alternator and also puts the charge lamp on. So no charge and no warning lamp...
I almost made it home - the RITA box gave up when the battery got too low, which was 11V according to my multimeter. Ian
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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I had that happen many, many years ago, suddenly left in the dark on a country lane. Culprit was a connector moving to the point it shorted to earth.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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The connector going loose is quite likely because of heating up and losing its springiness to grip the terminal, once it starts going just a bit loose the resistance goes up and so does the temperature. I used to get this on an old Mini I had. The electrical output for the entire car (the only exception being the starter solenoid) went through ONE (1!) 1/4" blade terminal, this used to go limp at frequent intervals and flatly refuse to send any more electrons through, due to simply getting too hot. |
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"Chicken nuggets don't dance on a Tuesday."
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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That's the weakness of those blade terminals. Seen that happen many times.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Dave P.
Senior Member Joined: 12 Jan 2015 Location: Northants Status: Offline Points: 5573 |
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Nooooo! 'Twas the terminal, the male Lucar thingy which is a part of the relay which was loose, though one could hardly tell so minimal was the movement.So the break in the circut was inside the relay.
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
1971 V7 Special. 1972 850GT. 1970 T120 Bonnie. 2009 500 Bullet. |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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I had that on my Stebel horn, the relay supplied with it (Made in Italy) was so well designed that thespade was moulded into the base and the telay gubbind fixed inside the case and the two just pushed together. Within a week or two that pressed together joint made no connection. I fitted a proper relay from a proper manufacturer. |
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Dave P.
Senior Member Joined: 12 Jan 2015 Location: Northants Status: Offline Points: 5573 |
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I fitted a proper relay from a proper manufacturer. Quote Brian.
I thought I had done that. Maybe it was a rougue one. I hope the replacement is better. |
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
1971 V7 Special. 1972 850GT. 1970 T120 Bonnie. 2009 500 Bullet. |
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