Author Topic: Lights not working (1965 B40F)  (Read 558 times)

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Phil C

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Lights not working (1965 B40F)
« on: 10 January, 2019, 13:11:41 »
Hello everyone, I'm trying to find out why my headlight and tail light have stopped working (but stop light and horn work okay.) 
I've charged the battery and it is showing about 6.2v, so that's okay.
Tested the headlight bulb: okay.
So I guess the next step is to check power is reaching the switch. Here is my first stupid question of the day (please see photo attached): does the black plastic bit just pull off the metal bit to expose the connections? (I'm guessing so but don't want to pull too hard in case not!)
Thanks in advance.
Phil.

Phil C

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Re: Lights not working (1965 B40F)
« Reply #1 on: 10 January, 2019, 13:15:23 »
Here's the photo.

JulianS

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Re: Lights not working (1965 B40F)
« Reply #2 on: 10 January, 2019, 13:43:40 »
Yes just gently pull it off.

Photos show what you will see.

I suggest you also check the dip switch.
« Last Edit: 10 January, 2019, 13:47:03 by JulianS »

Phil C

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Re: Lights not working (1965 B40F)
« Reply #3 on: 10 January, 2019, 13:49:48 »
Thanks very much Julian. I'll let you know how i get on.   Phil.

Phil C

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Re: Lights not working (1965 B40F)
« Reply #4 on: 10 January, 2019, 14:16:22 »
Her'e what I found when I pulled the switch apart (see photo). I guess the wires simply push in?  Don't seem to want to pull out though?

Anyway, I set my multimeter on DC volts and connected one end to the battery and pushed the other end into connection 2 on the switch, which I believe is incoming to the switch from the battery via the ammeter. I expected to get either about 6v or 0.  But I got about 4.5v.  Why could that be? Something wrong at the ammeter?   

Phil.

Phil C

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Re: Lights not working (1965 B40F)
« Reply #5 on: 10 January, 2019, 14:42:45 »
I've just lost and regained my connection to the website so this might come to you twice - sorry if it does.  Anyway, I'm confused. Having measured 4.5v at the light switch, I checked the voltage at the ammeter.  Where three wires leave the ammeter, I got 4.5v. Aha, I thought, if there are about 6v where the single wire enters the ammeter, then the problem is at the ammeter. But the reading was 0.  How can that be?   Phil.

Bees

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Re: Lights not working (1965 B40F)
« Reply #6 on: 10 January, 2019, 16:00:01 »
I am far from an expert on wiring, but surely it's a process of elimination.

Looking at a wiring diagram of a B40, you've got one wire from the negative terminal of the battery that goes to the ammeter, it should be brown and white according to the diagram I found.

If you put one probe of the multi meter on the ammeter terminal where that wire connects and the other on to the positive terminal of the battery (if you can reach it) do you still get 6v. if you can't reach the battery any metal part of the bike should do.  if the multi meater doesn't read 6v then there is a problem in that length of wire, if you've got 6volts then you know the wire is sound. Then try the other ammeter terminal to see if the problem is in the ammeter.

persistance pays off.
« Last Edit: 10 January, 2019, 16:07:10 by Bees »

Phil C

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Re: Lights not working (1965 B40F)
« Reply #7 on: 10 January, 2019, 16:06:41 »
Our messages passed in the ether I think Bees!  Phil.

Phil C

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Re: Lights not working (1965 B40F)
« Reply #8 on: 10 January, 2019, 16:23:12 »
Except mine doesn't seem to have reached the site

Phil C

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Re: Lights not working (1965 B40F)
« Reply #9 on: 10 January, 2019, 16:30:13 »
Again, two of these might arrive, as I'm having a bit of computer trouble.   Here's an update in case anyone is still interested: walking the dog, I had a brainwave: maybe I connected my meter to the wrong terminal at the battery! So when I got home I put it on the +ve (earth) terminal and got readings which make a bit more sense:  very little at the switch; less than half a volt where three wires leave the ammeter; 6v where the single wire enters the ammeter.  So I guess the problem is either a duff ammeter or a duff connection there.

It does help if you connect the meter to the correct terminal! Not sure where the 4.5v came from when I wrongly connected.

Phil.

Bees

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Re: Lights not working (1965 B40F)
« Reply #10 on: 10 January, 2019, 17:01:02 »
It seems logical to me that it's a problem with the ammeter as 6v has to find its way through the ammeter where it gets split into 3, one for the main bulb, the side light and ignition.

I've got to replace my ammeter on my bike later I'll see if I get the same reading on both sides of the ammeter and post back.


Phil C

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Re: Lights not working (1965 B40F)
« Reply #11 on: 10 January, 2019, 17:30:24 »
I've checked the connection and it appears sound, but no volts there. So I guess the ammeter is a gonner?   Phil.

Bees

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Re: Lights not working (1965 B40F)
« Reply #12 on: 10 January, 2019, 19:22:55 »
Looks like it is. Just checked mine and I get the same reading on either terminal.


Bees

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Re: Lights not working (1965 B40F)
« Reply #13 on: 10 January, 2019, 19:27:09 »
I expect this will sort the non start problem too as the coil probably not getting 6v either.

Worth checking just to see. With the ignition on put the multimeter probes on the coil pos and neg.

Phil C

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Re: Lights not working (1965 B40F)
« Reply #14 on: 10 January, 2019, 19:38:52 »
Okay thanks Bees, I guess I'll order a new one (these old bikes are money pits, aren't they?!)

I suppose it's best to get the Lucas one if it fits.  And I imagine there'll be an "O" ring or felt washer or something underneath the bezel.

Fingers crossed.

Phil.