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D7 Lighting Coils
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gpo746
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June 14, 2019 - 11:37 am
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I have a twin switch D7 '66 6v Positive earth , could any of you wise ones out there be so kind as to tell me what the resistance of the lighting coils are when dark red and white wires not screwed to the plate ?(so not to skew the readings) Please . Also, what the AC voltage readings off these two wires are when bike is running under load ?(with lighting on)  Tickover AC Voltage and Highest it should go upto. Reason I ask is because I have blown bulbs AND have fitted a Rex Caunt Regulator ,bulbs still went floodlight bright and blew!. I have a new Lucas wiring loom , all earths are spot on ,fresh 6v battery etc. Help would be greatly appreciated Thanks.

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Mags 1
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June 14, 2019 - 11:53 am
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The wire on the lighting coils is quite thick, so quite low resistance to current flow, only a few ohms will you find.

I've had readings of 30 volts ac from these and charging coil too on my Bantams, especially so when you have good magnets in the rotor, but 8 to 10 is a regular seen voltage on lighting coils output. That's why folk advocate a voltage regulator I suppose.

Tickover voltage on lights coils will fall below six volts generally, the idea is to only use the full lights whilst moving, I think.

I wonder if someone has converted your lighting coils to 12 volts by connecting the coils in series? Parallel is the normal way, ie, both starts together and ends of coils connected together.

Four now on the road and at least several in bits.

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sunny
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June 14, 2019 - 3:35 pm
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the  things   you   ASK    WILL NOT   help   you  fix  it        ,,you  need  to  follow   the    INFO    that  comes  with  both   the  new  LOOM & REX s  regulaytor     ,,,   thers   lots of    2 switch   looms   the   NORTON  JUBLE  is just   one    ,,and  as  far  as i know  the  3  wiering   systems  fited  to  the D 7  modles   dont   fit   each  uther  so   you  need  to  find  some of  my preveus   posts     for  moor   info ,,   the  D 7  wiering  dyagrams   will  help    ,, NOT  A   LOT    but   have  a   look  anyway

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gpo746
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June 14, 2019 - 7:05 pm
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Hello Sunny,

Thanks for the reply . Why would my initial enquiry not help me solve it? The idea is to ascertain if the coils are out of spec etc. The loom is THE CORRECT one for a 1966 twin switch D7 , all the wiring is correct as I have checked and re-checked . Loom is Lucas direct replacement for Wipac S3536WW19212L.jpg

As for Regulator instructions ,I have connected in Parallel as per Rex's instructions .It is simple , 1 red wire on the regulator . Where the dark red wire from the stator plate joins the harness I replaced the single female bullet connector with a double female and re-connected dark red from stator to loom and put red wire from regulator into that . Regulator is well earthed to bracket where rectifier is .

Mags 1

Thanks for your reply as well . I am also seeing 25~30 volts AC when I rev it abit and about 8v AC with lights on on tickover . 6v AC nominal on tickover with no lights on . Coils are showing 0.2 ohm on digital meter and around 1 ohm on my AVO meter . Digital meter is abit crap so I will stand by the Avo reading . I will have a look at the coils tomorrow but out of interest I have put a 12v Headlight bulb in and it does not blow BUT it is SUPER bright when revved 2-3k . I put a 12v speedo bulb in too but this was a dull glow until revved and it got adequately bright.

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Mags 1
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June 14, 2019 - 7:51 pm
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Lucas stuff is made in another country now I believe, so not even the name is British now, let alone the products, your new harness was probably quite expensive, but I'm afraid that guarantees nothing any more these days.

Rex knows his Bantams alright and will get you sorted I'm sure, did he sell you the harness?

Four now on the road and at least several in bits.

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mikef
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June 14, 2019 - 8:25 pm
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The rex Caunt 6V AC regulator should limit the AC voltage to the lighting circuit. It seems that you have connected it correctly. The red wire to the dark red from the generator. The dark red wire from the generator, as you probably realise supplies the lights.
Are you absolutely sure that the earth to the regulator is good? Is the bracket well earthed to the frame?
I know that these regulators do work, I suppose it is just possible that yours is faulty.
I would suggest that you check the voltage between the metal tab of the regulator to the red wire, if this goes up to 20 odd volts then the regulator is faulty.
I would also that you check the wattage of the bulbs that you have fitted as even without a regulator the bulbs should not normally blow.
The only thing that normally causes problems is the aftermarket ducon dip switch. It is break before make, instead of make before break. It normally just blows the rear lamp. then the rear lamp having blown puts extra power into the head lamp and can blow that.
Wattage of the D7 headlamp should be 24 if I remember correctly, the rear lamp is 5.

Good luck.
         Mike.

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Mags 1
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June 14, 2019 - 8:32 pm
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mikef said

Wattage of the D7 headlamp should be 24 if I remember correctly, the rear lamp is 5.

Good luck.
         Mike.  

30/24 if I remember correctly Mike.

Four now on the road and at least several in bits.

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sunny
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June 14, 2019 - 9:54 pm
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the  D7   1704  geny  was      for    the   2 swich  d7  only      from  Bsa  its  isnot  interchagable  with  uther  looms  ,,     3536   is NOT  the  nuber    i     have   for  the   loom     that  gos  with   the  1704  geny          ,,,  the  1704  geny   can  pok  out  upto  20 volts  if  wiered  rongly     you   need  to do moor  checking   to  find wots   rong        loom  nunber  for  D7  are  3348  ,, 3347 &   3538    

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mikef
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June 14, 2019 - 9:55 pm
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I think the D7 was 24/24 W but could be wrong. The D14 was 30/24 W.

Just going to check the manuals now. You've made me think.

Mike.

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sunny
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June 15, 2019 - 8:54 am
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6 watts  in  the  haedlamp   only   make  a  problam    wen  useing a  NON   BATERY  SYSTEM        ,, i think   the   regulaytor    being   used   isNOT  compatable    with   the  2 sw  D7  system       as  its   odd   in  BANTAMS   also ,,  its   is  the only  one   that  works  in  the  way  it  dose the   singel  switch D7   allmost   alike    but dont   need  an   Emegance   to   swich  in   if  the  baterys    flat

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gpo746
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June 15, 2019 - 10:35 am
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Hello mikef

The wattage of the bulb is 30/24w . 24/24w don't seem to be available these days. Yes, the voltage goes upto 25v + AC when connected to dark red wire and to casing of Regulator. Earth is spot on . Did a "bleep" test with my digital meter one proble on engine one on casing of regulator. spot on. It is the same with all the earths / earthing points on the bike.

Mags 1

I bought the loom direct from Wassell (a friend has a trade account) here are the details I pulled from their site

** Please log in to view ** WIRING HARNESS - Lucas,BSA
Genuine Lucas Twin switch Coil Ignition Main wiring Harness. As fitted to BSA Bantam D7 models (1963-66).
Direct replacement for Wipac S3536.
Supplied with Switch sockets.
Premium quality cloth braided wiring harness!
Supplied boxed, and with colour coded wiring loom installation plan.

Coil Ignition Main Harness: Yes
Made in England.
Lucas is a registered trademark of Lucas Industries Limited

Connections seem to be identical inside the sockets . only big differences are the earth colour . instead of transparent it is white with blue tracer..not a problem . Colours to rectifier are the same. I am using a silicon square 35A rectifier but that should make no odds here as that is for the DC side of the system NOT the AC lighting side. DC lighting only comes in on the L position for pilot and tail so I believe.

Hello Sunny,

The Genny is indeed a 1704 . The regulator I am using is this one :

** Please log in to view **

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sunny
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June 15, 2019 - 11:06 am
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im    not   inprest  with   regulator     in   use  on  bantams        the   output  is  to  low     from  the  geny  useing   a  6 volt  system       a  12 volt reg/rec   is beter      &  upgrade    the  lot    with  a  D 1 or  3   geny  ,,,     or  as  i  do     stik    to  the old  system    ,, you  can  get  regultors on  E BAY    for  just  £ 3,50      but   not   werth  it   to  me      so   i  serjest you  bin   that  reg     as   you   have  the  rest   for  6 volts 

its  all   FUN     as i  say   keeps   us   bizy    ,,  you   mite  like to   get  the  genny   certyfied on here  as  the  coils  mite  NOT  be  as  the  nuber  says   1704

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gpo746
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June 15, 2019 - 3:44 pm
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Hello Sunny,

I will return it to Rex I think. If it cant handle being used on a Bantam then its £28 down the swanny . I am not rich and cannot afford that . I winched when I bought it !

How do I get the coils certified?

Thanks

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mikef
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June 15, 2019 - 5:31 pm
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Maybe worth checking the generator coils. The outer two should be wired in parallel with one end going to earth and the other to the dark red wire (generator terminal 3).
Resistance of these coils in parallel would be low, never actually measured it but maybe less that 1 Ω.
The centre coil should have no connection to earth or the other coils, it is used for battery charging only and goes directly to the rectifier.
It is possible that someone has wired all three coils in parallel at some time in the past. This could give excessive power to the headlamp when a standard wiring loom was fitted. It would also upset the battery charging of course.
Certainly it seems that the regulator is faulty but it is worth checking exactly how the coils are wired. Maybe if all three coils are wired in parallel the generator could output enough current to destroy the regulator, unlikely though, I would have thought.

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sunny
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June 16, 2019 - 8:11 am
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  sorry   GPO   a  verry  poor   choise   of  word  on  my  part     if you  get  time   a  photo   of  the  geny  coils  on  here  will  help  use   conferm   its a  1704  geny

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gpo746
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June 17, 2019 - 6:22 pm
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Here is the stator plate . It is marked 1704 and the red tails are together on to No.3DSCF4530-1.JPGDSCF4531-1.JPGDSCF4532-1.JPGDSCF4533-1.JPG

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Mags 1
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June 17, 2019 - 7:58 pm
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Looks like one wire is bared and shorting out to earth???

Four now on the road and at least several in bits.

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gpo746
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June 17, 2019 - 10:41 pm
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Mags 1 , No, it is just old oil on the sheathing from over oiling the cam felt pad  ..besides it is the white wire which I believe is earth anyways .

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sunny
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June 18, 2019 - 8:43 am
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hi  GPO   the  magnet   ROTOR   has   been  rubing  on the  coil stator  LEGS  that  means   the  oilite  BUSH   needs  CHANGING    ,,oil   must   also  run  from  the   felt   pad  to  the BUSH   utherwize  it  dont  get  oiled  so  thats  wy   its  needs  chaging  if  you  get  time  FILE   a  sharp  edges   away      so   the  sheathing   gets  a  chance   to  do  its   JOB     &  the  coils   are   a  set  No  1704       the  RED  wier  from  post  3  going  to the igniton  s/w  gets  reruited  to   H/ lamp ,, the  ciols  look  o/k   but  may  stil  have  an  earth  short

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gpo746
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June 18, 2019 - 8:53 pm
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Hello Sunny, Yes, I have an oilite bush on order already . The sheathing is doing its job it just looks bad because of the old oil. I have checked the windings and there are no shorted turns as there is 0.02 ohms reading  . Still baffled why we are seeing 25 ish volts max AC ? What is the best way to regulate it then?

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