Classic cars forum & vehicle restoration.

[FAB Cruiser]

My wife has a 1966 MGB which is positive earth / dynamo.

I'm thinking of replacing the loom and switching to negative earth / alternator.

My question is should I use a new '66 loom like the original, get that working with everything 'as is' and then do the switch to Negative earth (changing the dynamo for an alternator, modifying the rev counter, replacing the fuel pump etc),??

OR.. Should I install a 1969 onwards loom, which was the first year offering negative earth and wired for an alternator with integral regulator??

My guess is it doesn't really matter.

The advantage of the first option is it gets broken down into two stages and I can prove the re-wire works before moving on to the polarity change. Also with a '66 loom, the connectors should be correct for all the original ancillaries.

At least everything is available 'off the shelf' unlike my Zephyr!

Thanks
David

[Nic Jarman]

If you replace the loom first it will end up as a much neater job. If you can find a '69 or later B take loads of photos so you can see all the differences. Good luck.
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1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush

[FAB Cruiser]

Hi Nic,

Do you mean I should use the earlier or later loom?

I have a 72 roadster as a reference but haven't looked at the differeneces in detail as the 66 only arrived this week. The early loom will be right for things like no reverse lights, single speed wiper etc.

Cheers
David

[ukdave2002]

Firms like Autosparks will make a custom or modified loom up for you..

[Nic Jarman]

Use the later loom as it will have all the wires you will need. You may have to relocate the odd component and lose the control box. Its a big job and worth doing well.
_________________
1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush