1972 wiring diagram: something wrong?

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pierodn

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Hi All.
I mounted the new harness as required by the 1972 wiring diagram (master switch 4 positions). 
The 1972 wiring diagram says that the two positions light switch may be set only with  U and UY wires.
But in this way the rear light doesnt work! the stop yes.
After fitting to the two position light switch in addition to U and UY even the NG wire (like in 1971 wiring diagram but that provides only NG and U wires to the two positions light switch and a 3 positions master switch without UY) everything works perfectly!
Why?
 
pierodn said:
I mounted the new harness as required by the 1972 wiring diagram (master switch 4 positions). 
The 1972 wiring diagram says that the two positions light switch may be set only with  U and UY wires.
But in this way the rear light doesnt work! the stop yes.
Click to expand...

Yes, with the 4 terminal ignition switch, the tail, pilot and instrument lights [NG] are fed from terminal '3' of the ignition switch, and the headlamp has a separate feed [UY] from terminal 4.


pierodn said:
After fitting to the two position light switch in addition to U and UY even the NG wire (like in 1971 wiring diagram but that provides only NG and U wires to the two positions light switch and a 3 positions master switch without UY) everything works perfectly!
Why?
Click to expand...
If I understand correctly, you are using a 3 terminal ignition switch (the ignition switch numbers on the wiring diagram refer to the terminal numbers)? By connecting NG to the headlamp switch you will have wired it the same as shown on the 1971 wiring diagram.


The change to the 4 terminal switch appears to have been made so that parking lights are selected at the ignition switch-but without the facility to also switch on the headlamp.
 
Hi Les.
Sorry but i didnt understand what you mean.
I have a 4 master switch like says the 1972 wiring diagram for 1972 harness.
But with UY on the 4 and NG on the 3 from the master switch to the light switch all works (first right switch the parking light with pilot only, second left no power, third left power, four power and front light and stop but no rear light.
If i fit a NG too to the light switch (with U and UY) on the 4 the rear light works but the 1 the parking light works with pilot and hiah beam!
Thank you.
Piero
 
pierodn said:
I have a 4 master switch like says the 1972 wiring diagram for 1972 harness.
But with UY on the 4 and NG on the 3 from the master switch to the light switch all works (first right switch the parking light with pilot only, second left no power, third left power, four power and front light and stop but no rear light.
If i fit a NG too to the light switch (with U and UY) on the 4 the rear light works but the 1 the parking light works with pilot and hiah beam!
Click to expand...

I think I understand. By connecting NG to the lighting switch, the NG circuit (pilot, tail, instruments) is being fed from UY.

If, as you said, the NG circuit does not work when NG is only connected to master switch terminal 3 then the master switch may be faulty, so check for voltage at terminal 3 when the key is at the first (park) and fourth (ignition and lights) positions.
 
Also, are you sure you have the master switch wires connected to the correct terminals?

Although the terminals are numbered clockwise 1-4-3-2 on the wiring diagram, the original Lucas switch terminal sequence is: 1-4-2-3.

1972 wiring diagram: something wrong?
 
Hi Les,
You have understand what happened, sorry for my bed explanation.
Me too thought the problem was the master switch that was not working fine!.
So i have taken another 4 positions master switch from another bike, a roadster " well working".
Well, the problem remained the same, the rear lights continued to not turn on!!!!!! also with the other master switch.
So i checked into the light shell of the other bike " well working" and with a lot of surprise i have seen the NG wire fit to the switch with UY and U!!!!!!!
The bike "well working" was never molested from me and so the modification was not done from me before!
What is the problem?
Thank you.
Piero
 
pierodn said:
Me too thought the problem was the master switch that was not working fine!.
So i have taken another 4 positions master switch from another bike, a roadster " well working".
Well, the problem remained the same, the rear lights continued to not turn on!!!!!! also with the other master switch.
So i checked into the light shell of the other bike " well working" and with a lot of surprise i have seen the NG wire fit to the switch with UY and U!!!!!!!
The bike "well working" was never molested from me and so the modification was not done from me before!
What is the problem?
Click to expand...

From what you have described, unless there is a fault in the new wiring harness, I can only think that an NG wire is not connected correctly somewhere, or, a bad tail lamp earth/ground has been known to cause problems?
 
In a previous thread, it was mentioned that some (early?) 1972 models apparently had an NG connection to a 3-position lighting switch, not shown on any 1972 wiring diagram, (but there doesn't seem to be any logical explanation for doing so when a 4-terminal master switch is used)? :?

1972-wiring-t11940.html#p138148
 
L.A.B. said:
pierodn said:
Me too thought the problem was the master switch that was not working fine!.
So i have taken another 4 positions master switch from another bike, a roadster " well working".
Well, the problem remained the same, the rear lights continued to not turn on!!!!!! also with the other master switch.
So i checked into the light shell of the other bike " well working" and with a lot of surprise i have seen the NG wire fit to the switch with UY and U!!!!!!!
The bike "well working" was never molested from me and so the modification was not done from me before!
What is the problem?
Click to expand...

From what you have described, unless there is a fault in the new wiring harness, I can only think that an NG wire is not connected correctly somewhere, or, a bad tail lamp earth/ground has been known to cause problems?
Click to expand...

Hi Les,
i mean.
But the rear light system works well because on the first switch (bike parking)
the rear light is on!
I means all the wires are connected.
Thank you.
Piero
 
L.A.B. said:
In a previous thread, it was mentioned that some (early?) 1972 models apparently had an NG connection to a 3-position lighting switch, not shown on any 1972 wiring diagram, (but there doesn't seem to be any logical explanation for doing so when a 4-terminal master switch is used)? :?

1972-wiring-t11940.html#p138148
Click to expand...
Hi Les,
I agrre that with 4 positions master cylinder you dont need a 3 light switch position.

But with 2 position too without NG the rear light doesnt work the same.

But the other Roadster with 1972 wiring harness has a 3 positions light switch with NG wires!!!!!!
May be the previous owner had the same my problems?
Thank you.
Piero
 
I would say that with two or three light positions switch, you always need the NG connect to have the rear light on the bike starting.
Ciao
Piero
 
pierodn said:
I would say that with two or three light positions switch, you always need the NG connect to have the rear light on the bike starting.
Click to expand...

Well, no, not really as NG (pilot, tail, and instruments) should be fed directly from the master switch terminal 3 when at the "ignition and lights" master switch key position (4) so there should be no need to power NG from the separate headlamp supply [UY] as the whole idea of keeping the two circuits separate is so that the headlamp is isolated when the master switch is turned to the "parking lights" key position (1).
 
pierodn said:
I mean, but as x 1972 wiring diagr the rear light works only in parling position!
Click to expand...

According to the 1972 diagram, manual and riders handbook, the (running) lights should work at "Park" (key 1) and also at "Ignition and lights" (key 4).

1972 wiring diagram: something wrong?


At "Park", master switch terminals 1 and 3 are common, and at "Ignition and lights" all four terminals are common.
Although the wiring diagram is a schematic drawing so is only a basic representation of the circuitry it does show an NG wire running directly to the tail lamp from master switch terminal 3 therefore logically, the tail lamp should work independently from the headlamp switch.
 
Hi Les,
i agree.
The only thing i can think is that of the 4 position the 3 NG terminal is not common with 1/2/4 terminals!
If this were true, it is not a failure of my master switch because the same happens with the other one.
Thanks.
Ciao
Piero
 

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