Converting to Negative Earth

[trish1400]

Just wondering if anyone has converted their positive earth Bedford to negative earth?

I believe you can ‘flash’ the dynamo but if you don’t drive it regularly it’ll go back to positive earth.

Any tips, thoughts, instructions?

Thanks!

[daveglanfield]

hi trish
you or right about flashing the dynamo but you have to swap the battery terminals round . and then its negative earth
it is impossible to go back to positive earth
hope this helps
dave glanfield

[trish1400]

Thanks Dave, good to hear from someone who has done it.

I’m still a bit worried about the dynamo reverting to positive earth though. The flashing will only change the magnetism in the coil to a degree, it will always retain some of its original magnetism. To be honest I’m way out of my depth here but it has something to do with remanence and magnetic hysteresis.

Back in the 1970s my Dad converted my grandfather’s fishing boat to negative earth and after my grandfather died my uncle took it on, only he didn’t use it for months and when he tried to start it sparks started flying. The coil had reverted to its previous magnetism and therefore the battery was connected the wrong way. Dad says as long as the dynamo is used regularly it shouldn’t be a problem but we’re not sure what that means in practical terms; e.g. if the van isn’t driven for a month will it still be ok?

Anyone got any idea? Or can lots of people vouch that they’ve never had a problem and therefore I should just get it done.

Thanks,
Trish

[grumpydad]

Hi
why not just fit a alternator
you will get a better charging rate as well
its quite a easy job
if you get the right alternator
its about 2 hours work
the hardest thing is to find a fanbelt to match
but if you do it i will mesure mine and let you know the size

[trish1400]

Hi,

Thanks for that. We did think about changing it to an alternator but were worried that the stress on the water pump bearings would be too high. Is that not a problem?

How many amps is your alternator? Dad’s got a 50 amp one kicking around.

Any information you can give would be really useful!

Thanks,
Trish

[grumpydad]

Hi
wyh would you put more strane on the water pump
the belt would be no more tight than a dynamo
the alltner will be handed
you will need one fron a ford
all the bmc ones are on the wrong side

as for the wireing that is very easy
on the back of the aultnater
you have 3 terminals 2 big and one small
the 2 big ones go to the battery
use wire that will carrey 30 amps for each one
or the live side of the solniod
that leves 1 small terminal
find the ingintion light wire
on the reglater and put this on the small one
job done
if you put up a wireing drigram
i can tell you witch wire goes to the small one
for the ingintion light

a spell check on the post page would help me a lol 😀

[trish1400]

Hi,

Sorry, must have not clicked View on a notification email so I stopped getting notification emails (gets me all the time).

Thanks for the reply. Fixed the dynamo again this weekend but it’s days are numbered. Next time I’m taking your advice and switching to an alternator.

Thanks for the info.
Trish

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