The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: stev60 on 07.01. 2020 02:56

Title: Lucas U39
Post by: stev60 on 07.01. 2020 02:56
On the face of it these would appear to be  simple to wire in, Ive struck the same problem with two switches,and probably missing something simple. these are replica ones with a terminal connected to the centre by copper strips and a copper plate to take bullet connector for power source, is there a diagram to show exactly how these are wired 
Title: Re: Lucas U39
Post by: Greybeard on 07.01. 2020 09:30
Title: Re: Lucas U39
Post by: Swarfcut on 07.01. 2020 10:29
Stevo, It's more likely to be the switch, not you.

 Thanks to GB's link you can see the basic wiring for the switch.

  Check the switch actually works with a continuity test. As a pattern part there is a good chance the wiper to the centre actually connects to nothing and is for display purposes only!

 If the fault is the switch, worth digging apart to see if it is a simple assembly error on both of them, rather than a complete manufacturing pattern part replica copy take the money fiasco.

Title: Re: Lucas U39
Post by: stev60 on 07.01. 2020 18:57
Yes your right im sure ive got to dud switches the continuity check proved it , if I pressed hard enough on the lever I got a reading but not what it should be, really they are junk and taken up a lot of time, made in India, Ive noticed there are wassell brand switches but where they are made now one wonders, thanks for the link Greybeard   
Title: Re: Lucas U39
Post by: Swarfcut on 08.01. 2020 09:00
Stevo... In the short term rewire the switch to be a simple single pole on/off.

  Set the switch to L or H and put power to one pillar and feed the dipswitch and rear light from the adjacent pillar. The "clicker" bridges these two contacts. Any failure here can only be due to poor conductivity, so a good scrape of the surfaces will help. Forget speedo and pilot for now. Not strictly correct, but better than simply dumping a poor purchase.

 As you have found with pattern parts they all require some sort of attention. With world wide distribution and low cost Indian and S.E. Asian production, even choosing a well established brand is no guarantee of quality, borne out by experiences related elsewhere on the Forum.

Title: Re: Lucas U39
Post by: stev60 on 08.01. 2020 18:50
yes ive looked at that option and it works , I can also put the power through the terminal that holds the body of the switch in which powers up the whole switch only problem there is it the off position it leaves the pilot light on, I will have another look this afternoon, one switch is complete crap it came on a new headlight for another bike, the other looks well made both are branded Minda one has flats for retaining clip the other dosent, it maybe I will have to look at $50 for another one with the fear it will have the same problem, the other option is wassell. Thanks
Title: Re: Lucas U39
Post by: stev60 on 09.01. 2020 18:49
Ive worked it this way , power from amp meter to terminal 3 with tail light wire clik one way for pilot and otherway for dipswitch terminal one can livened from original power feed giving an option for some thing else. on this switch I cant quite work out why terminal 6 would become live purposely when switch is in off position although ive seen photos of a wire in this terminal. There is no continuity at all so it is a dud but will still work
Title: Re: Lucas U39
Post by: stev60 on 27.01. 2020 18:21
Just quickly back to these switches, Ive had three over a period that had problems so there must be a few duds our there, to get the  one I had problems with on this occasion I drilled another hole for the spring a little further around so the clicker picked up the first  terminal for dipswitch, second was tail and power from amp and third pilot , then dead terminal for off . Works as should .
Title: Re: Lucas U39
Post by: BSA_54A10 on 28.01. 2020 11:20

I rather thing that this diagram is actually wrong
Title: Re: Lucas U39
Post by: edboy on 07.02. 2020 19:29
i have always had problems with these switches. usually in winter coming outside and finding the battery totally flat where the insulation fails.the solution is to wire a ignition switch into the circuit between the battery and light switch with a pilot light to tell you ignition is off or on.