change from pos - 6v to neg - 12 v

[sean]

1962 super rocket
lucas El 3 dynamo 6v
DVR 2 N [new]
instructions with the DVR2N say to disconnect the F and D wires running from dynamo
connect the - terminal to ground and run a jumper from the pos terminal and flash the green F wire you should see a spark
My problem is I dont get a spark ? [ if I touch the jumper from pos to a ground I get a big spark ]
I have checked fuses
I have a new 12v gel battery 12.8 volts
the dynamo was charging fine in its previous 6 volt pos earth configuration .
any suggestions appreciated I am no electrical wizard .....why do you need to disconnect the D wire if your only flashing the F wire ?
thanks in advance
Sean

[limeyrob]

Battery must be connected negative to frame/earth.  Have you done that?
Feed to ammeter must be on positive with a fuse (say 20A)
Dynamo is not connected so you have F and D terminals.
Now take jumper from battery pos to F and stroke it across.

As a test you can take the dynamo chain off (yes its a faff) and motor the dynamo by putting 12v pos to both F and D and checking it spins the right way.

[Triton Thrasher]

Sounds like either the other end of the field coil is not connected to the casing or there’s a loss of continuity (break) within the field coil.

[sean]

Battery must be connected negative to frame/earth.  Have you done that?
Feed to ammeter must be on positive with a fuse (say 20A)
Dynamo is not connected so you have F and D terminals.
Now take jumper from battery pos to F and stroke it across.

As a test you can take the dynamo chain off (yes its a faff) and motor the dynamo by putting 12v pos to both F and D and checking it spins the right way.

Battery neg is connected to ground via 10 amp fuse
charging system was working fine on previous 6 volt pos earth
feed to  ammeter pos side reads 12.8 volts
taking the chain off will be a last resort

[sean]

Sounds like either the other end of the field coil is not connected to the casing or there’s a loss of continuity (break) within the field coil.

charging system was working well on the 6v pos earth system

[groily]

As a test you can take the dynamo chain off (yes its a faff) and motor the dynamo by putting 12v pos to both F and D and checking it spins the right way.

That's quite true and motoring with neg earth will re-set the polarity (or confirm it if you've already succeeded in reversing it without noticing).
Reversing dynamo polarity will not affect its direction of rotation though, unless you have inadvertently swapped  the field coil or the brush connections by mistake.
So you shouldn't have to go through the faff with the chain really!
This is a good layman's guide:
https://www.matchlessclueless.com/electrical/lucas/repolarising-lucas-dynamo/

[Swarfcut]

 These are the most annoying faults, turning a simple modification into a hammer thro' the tank moment. So start at first principles.

 Dynamo was working fine, so a headlamp bulb or meter across a D-F link to earth establishes whether the dynamo is still giving any output. As TT notes, field coil connections/integrity are number one suspects, also dynamo body earth connection also something to consider. Service Sheet 809 gives basic test procedure.

 Big spark from battery  pos to earth shows for now the battery is good and battery earth connection is fine. A test meter from your pos jumper to F should indicate continuity if all is in order. Maybe you are expecting a BIG Spark.....as the current is fed through a coil with resistance, only a smaller one is to be expected. Could be all is as it should be, plenty on the Forum about waking and repolarising reluctant dynamos.

 Swarfy.

[chaterlea25]

Hi All,
Sean, what regulator was fitted for the 6 volt setup?
Asking because if it was not a Lucas type it could be that the internal field connections are wrong for the new setup

John

[sean]

As a test you can take the dynamo chain off (yes its a faff) and motor the dynamo by putting 12v pos to both F and D and checking it spins the right way.

That's quite true and motoring with neg earth will re-set the polarity (or confirm it if you've already succeeded in reversing it without noticing).
Reversing dynamo polarity will not affect its direction of rotation though, unless you have inadvertently swapped  the field coil or the brush connections by mistake.
So you shouldn't have to go through the faff with the chain really!
This is a good layman's guide:
https://www.matchlessclueless.com/electrical/lucas/repolarising-lucas-dynamo/

thanks
I have read through that article several times [ im old  ] there is a link on the DVR2 site today looks like the tank is coming off and going through the wiring harness built by a previous owner .

[sean]

Hi All,
Sean, what regulator was fitted for the 6 volt setup?
Asking because if it was not a Lucas type it could be that the internal field connections are wrong for the new setup

John

regulator was original Lucas

[sean]

These are the most annoying faults, turning a simple modification into a hammer thro' the tank moment. So start at first principles.

 Dynamo was working fine, so a headlamp bulb or meter across a D-F link to earth establishes whether the dynamo is still giving any output. As TT notes, field coil connections/integrity are number one suspects, also dynamo body earth connection also something to consider. Service Sheet 809 gives basic test procedure.

 Big spark from battery  pos to earth shows for now the battery is good and battery earth connection is fine. A test meter from your pos jumper to F should indicate continuity if all is in order. Maybe you are expecting a BIG Spark.....as the current is fed through a coil with resistance, only a small insignificant one is to be expected. Could be all is as it should be, plenty on the Forum about waking and repolarising reluctant dynamos.

tank is too expensive but I am getting there  I turned the lights off in my shop because I thought the same maybe its only a faint spark but nothing....  going to take the wiring harness apart its all taped together by PO and check deeper will look up the service sheet  but as I mentioned was charging fine past few years on 6v  pos earth thanks for all the suggestions everyone ......gives me an excuse to be in the shed and not working on wifes to do list  the bike is more important .

 Swarfy.

[groily]

Have you checked field coil continuity by measuring the resistance from the F terminal of the dynamo to the dynamo body, to follow up on what TT said a bit ago? There should be 2.8 to 3 ohms showing on a standard E3L. If it's 'open line' then the field coil isn't all there, for one of the reasons he gave.

Also worth checking the "bleedin' obvious" - that F actually IS F on the dynamo output terminals. D should be connected to a brush while F should disappear into the dynamo body where the field coil lives. It's not so very rare to find they've been hooked up the wrong way round if they've been on and off a few times.

[sean]

got it sorted
thanks for all the suggestions ....it was an aluminum bullet wire connector had oxidizing between the male and female ...put a jumper in the connector and then flash with the jumper from the pos and it worked .
going to clean everything up and put it back together .
Have a good day
Sean

[limeyrob]

Worth pointing out that bullet connectors seem to be a near random set of metals - steel, copper, brass, ally and quite a few of the combinations will get galvanic corrosion.  Unless it a perfect resto I would remove as many as possible and use longer cables and soldered joints. Solder is not perfect but it does give a good connection for longer. 

[sean]

Worth pointing out that bullet connectors seem to be a near random set of metals - steel, copper, brass, ally and quite a few of the combinations will get galvanic corrosion.  Unless it a perfect resto I would remove as many as possible and use longer cables and soldered joints. Solder is not perfect but it does give a good connection for longer.

and clean the flux off with isopropyl alcohol before shrink tubing