Author Topic: C11G battery does not charge when engine runs  (Read 1793 times)

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Offline Faster

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C11G battery does not charge when engine runs
« on: July 10, 2019, 10:49:57 pm »
After the engine stall ( been working for 5 min ), I use the multi-meter on the battery and I've got 6.07 V . The battery was fully charged 6.52 V prior the engine start to run .
I've made all the connections with a brand new Lucas harness with brand new components like ignition coil and rectifier ( the square one with 4 poles that works for 6 or 12 V ) .
I did follow the original BSA electrical diagram and did checked Lucas ( very basic ) just to confirm if I was doing things right . Everything it's working fine and I was careful identifying the alternator wires colors to match the greens of the harness and connect them on the right positions on the rectifier (2 ) and Switch (1)
Should I start checking the connections on the rectifier ? If everything is correct should I suspect the alternator ?

Offline chaterlea25

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Re: C11G battery does not charge when engine runs
« Reply #1 on: July 10, 2019, 11:22:39 pm »
Hi,
Does the bike have a PRS8 ignition and lighting switch?
To get these to work there are quite a number of linking wires (jumpers) that must be connected to get things to work as it should
the links are in this diagram (same as C11G)
https://bsac10c11c12.co.uk/smf/wiring-diagrams-91/lucas-1956-c12-(ohv)-wiring-diagram/

Its easy to test the alternator for voltage AC and DC at the rectifier

John

Offline Faster

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Re: C11G battery does not charge when engine runs
« Reply #2 on: July 10, 2019, 11:45:50 pm »
Hi John

I do have a PRS8 and I am not sure about the lightning switch !? I did follow the first diagram shown on the link you have sent . I was really careful regarding connections .

So , I will use the meter for AC on the two poles on the wires coming from the alternator ?

Online Ginge

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Re: C11G battery does not charge when engine runs
« Reply #3 on: July 11, 2019, 10:30:46 am »
Yes. Alternator can be measured with meter on AC.  Polarity doesn’t matter ( because it alternates)
Ginge.

Offline Faster

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Re: C11G battery does not charge when engine runs
« Reply #4 on: July 11, 2019, 09:57:43 pm »
Measuring the alternator on it's own , 3 wires , I have voltage in all 3 combinations ! Connecting them to the rectifier , dark green and light green , I have 0.15 V AC !

I presume there is a cat somewhere on the connections on the PRS8 , even tough , I checked a couple times .

I have 3 diagrams . One came with Lucas harness , colored , the lucas prs8 generic for 6V single cylinder machines and the BSA C11G 54-57 . There is a slight difference between the first and the other two . It's the position of the green and dark green on pin's 7 and 16 . On the first shows green on T7 and dark green on T16 the others shows the other way around . Lucas PRS8 shows a bridge between T5 and 6 that don't shows on the other two .
 Not sure if these details can influence the good working order of the circuit !

Offline chaterlea25

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Re: C11G battery does not charge when engine runs
« Reply #5 on: July 12, 2019, 12:41:06 am »
Hi,
Measuring with a meter is only a start,
Get a 12v headlamp bulb,
Test connect the bulb to each wire and the bikes chassis, the bulb should not light
connect it across each pair of alternator leads in turn,
it should give a dull light on one pair, a brighter light with one of the pair and the third wire
and no light on the other combination
Connect the pair that does not light the bulb together, and to one side of the bulb and the third to the other side of the bulb
This should light the bulb brightly on revving the engine a bit

Connect this combination to the AC connections of the rectifier directly, (with the loom disconnected)
Connect the headlamp bulb to the DC connections of the rectifier
It should again light the bulb brightly
Those tests will confirm that the alternator and rectifier are good, then we can proceed to the bikes wiring

John

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Re: C11G battery does not charge when engine runs
« Reply #6 on: July 12, 2019, 06:40:54 am »
If your using a meter with auto range they tend to show a residual voltage hench the 0.15 v or I may have read that wrong? John's idea of the lamp is a good simple test to check the alternator.if that works OK you can then move up the wiring to check the next bit.
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Offline Faster

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Re: C11G battery does not charge when engine runs
« Reply #7 on: July 12, 2019, 07:47:25 pm »
Thanks John for your well explained method to find out about the alternator and rectifier .
I will do that tomorrow and I'll leave you the outcome !
I feel more confident about the right way of doing it .
Thanks to Owen too .

The tech that rebuild the alternator was at my place yesterday and for him the alternator it´s ok ( made impedance checks and measure aC voltages coming directle from the alt  ). He was surprised about the absence of voltage on the rectifier soon the alt is connected to the harness . He did mentioned some of the tests but not all that John has described !

Offline Faster

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Re: C11G battery does not charge when engine runs
« Reply #8 on: July 13, 2019, 12:22:22 am »
Thanks Ginge for the tip !

Offline Faster

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Re: C11G battery does not charge when engine runs
« Reply #9 on: July 13, 2019, 05:48:14 pm »
Att. to : chaterlea25

Hello John

I've made all the tests and the results are exactly the same as you described . 100%

Just need to let you know the following .

The alternator have been repaired and the tech used 3 different colors for the 3 wires and left a sticker in each one !

Blue as green
Brown as dark green
Black as light green

I made the respective connections on the loom

On the 3 possible combinations using two of the wires  ( Alt ) on each time to see the density of the 12V lamp , I had the following results :
Brown + Blue = null
Brown + Black = weak
Black + Blue = strong

( I have got a feeling there is something wrong with the color combination ( stickers ) that was given by the repair shop ... just a guess )

I hope these information can lead you to the answer of the equation !

Lucas loom uses dark and light green on AC connections on the rectifier ! The one left , green , goes directly to PRS8 on T7 or T16 ( difference spoted between modern Lucas loom diagram and both Lucas generic PRS8 for 6V single cylinder and BSA C11G diagram .
« Last Edit: July 13, 2019, 05:55:51 pm by Faster »

Offline chaterlea25

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Re: C11G battery does not charge when engine runs
« Reply #10 on: July 14, 2019, 12:26:46 am »
Hi,
Here is where confusion can reign  ::)

I do not know the colours used on the new loom, so assuming it agrees with
https://bsac10c11c12.co.uk/smf/electrical-equipment-service-sheets/electrics-c11g-c12-(alternator-models)/

Did you join the brown and blue together and test the bulb to the black? it should give the brightest light
If this is so?

Then the Black is the common, this will go to one AC connection on the rectifier, along with the light green to the loom
The Brown will be the low output and go to the other AC connection, along with the dark green wire to the loom
The Blue will go directly to the loom connecting to 14 on the switch, mid green or green and yellow

I hope this works as its 00.24 AM
John

Offline Faster

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Re: C11G battery does not charge when engine runs
« Reply #11 on: July 14, 2019, 09:43:32 am »

Hello

The new loom uses light , medium and dark green .   Lucas part number B2
Yes , I join the brown and blue together and test bulb to the black . I have completed all tests . The results were the same as you described .

Following your logic , that is exactly the way they were and are connected .
Not sure about connecting mid green on T14 !!!? I think that goes on T16 on the old diagrams or T7 on the Lucas part B2 diagram !

Thanks for your help

João

Offline Faster

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Re: C11G battery does not charge when engine runs
« Reply #12 on: July 14, 2019, 09:12:04 pm »
Hello

I used the 2 diagrams attach as a reference ( plus the very basic Lucas B2 diag. that came with the loom . Difference is this one has T7 and T16 inverted )

Lucas PRS8 came already with the bridges established as shown on BSA C11G wir. diag. I followed all the connections from the loom to the switch using the attach diagrams as guidance . I've noticed the PRS8 typical diag. has one more bridge which I added. T5 to T6 ! I still did not tried without it to see if the absence of AC voltage on the rectifier still remains .

I think there is members in this forum that knows the C11G electrical connections by heart . I'll appreciate some feedback .

Offline ianinglis

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Re: C11G battery does not charge when engine runs
« Reply #13 on: July 14, 2019, 10:03:44 pm »
looking at the alternator its very easy to see how the 2+4 coil arrangement works -

between GB & WG - 2 coils charging
between GY & WG - 4 coils charging
if you join GB & GY and then check between the joint and WG - 6 coils charging
(which is what the light switch is supposed to do)



ian
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Offline chaterlea25

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Re: C11G battery does not charge when engine runs
« Reply #14 on: July 14, 2019, 11:04:27 pm »
Hi Faster,
I did say it was past midnight  :o
OK so not 14 but 16 and looped to 17

If you made a mistake wiring the switch? it is possible that the alternator output  is being shorted out?
Part of the design of the system is to short out the high output coils when the ignition only is on , 4-5 is closed, loop to 18 and closed to 17
The charging direct current depends on the loops  between 2 , 10 , 12 on the switch which are then connected to 13 when the ignition is turned on
The reason that the rectifier was not originally connected directly to the battery is because the old plate rectifiers had leakage and this would flatten the battery over time

Disconnect the wire to the loom that is also connected to the brown from the alternator and the blue that is going to 17 on the switch
Start the engine and see if there is AC present on the rectifier?

Enough for now
John