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Ray White
Joined: 02 Dec 2014 Posts: 6304 Location: Derby
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Posted: Fri Aug 23, 2019 11:57 pm Post subject: positive earth wire colour. |
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Probably something I should know but just can't remember...
Should earth wires in a positive earth car be red? |
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Bitumen Boy
Joined: 26 Jan 2012 Posts: 1735 Location: Above the snow line in old Monmouthshire
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Posted: Sat Aug 24, 2019 5:45 am Post subject: |
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I doubt it. My Herald was originally positive earth but all the earth wires are black, and the colour coding in the loom seems to follow the general conventions of the time. Of course there's always an oddball..! |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire
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Posted: Sat Aug 24, 2019 8:51 am Post subject: |
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Hi Ray
In the UK from the early 30's most vehicle manufactures adopted the Lucas standard in which all earth wires are black, regardless of vehicle polarity, certainly all vehicles in the Nuffield/ BMC group used this convention
Dave |
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Ray White
Joined: 02 Dec 2014 Posts: 6304 Location: Derby
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Posted: Sat Aug 24, 2019 10:12 am Post subject: |
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Thanks guys. I shall be completely rewiring my MG TC which is positive earth. At least I now know for sure that earth wires are black regardless of polarity.
The confusion came about because I was looking at the colour of battery cables. It seemed counter intuitive for a red wire to be connected up to a negative terminal. |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire
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Posted: Sat Aug 24, 2019 10:38 am Post subject: |
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Ray
My 57 MGA is 12v positive earth with 2 x 6v batteries fitted. From the factory all the battery cables had black insulation including the starter cable, the only exception is the positive battery to chassis (earth) which was a plain braided cable.
Dave |
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Ray White
Joined: 02 Dec 2014 Posts: 6304 Location: Derby
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Posted: Sat Aug 24, 2019 12:42 pm Post subject: |
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ukdave2002 wrote: | Ray
My 57 MGA is 12v positive earth with 2 x 6v batteries fitted. From the factory all the battery cables had black insulation including the starter cable, the only exception is the positive battery to chassis (earth) which was a plain braided cable.
Dave |
Dave. Unfortunately my car TC was hastily rewired 12 volt positive earth with a variety of black and red wires to earth. In fact the wiring had been so poorly executed I have had to strip it all out and will have to start again. I have ordered with a new harness from Autosparks via the Octagon MG car club. It will be a big bill but hopefully worth it. I am also fitting a new CS! electronic distributor and dynamator. It comes with a 45 amp wire and a TD pulley.
John Marks of Vintage Restorations who is restoring my instruments will be beefing up the ammeter to handle the extra output. |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire
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Posted: Sun Aug 25, 2019 10:26 am Post subject: |
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Ray
Coincidentally I fitted an electronic ignition distributor and a Stealth dynamator to the MGA when I restored it.
Unfortunately I had a parasitic current draw problem that would leave the battery flat after a couple of weeks if the car wasn't used, this was traced to the dynamator which was out of warranty (note to self don't buy these things until you need them!)
To stop the battery drain I fitted a relay that isolates the dynamo when the ignition is off; this was supposed to be a temporary fix some 4 years ago! The problem will almost certainly be a leaky diode in the units rectifier that wont take long or cost much to fix, your post reminded me its another job on the list!
Dave |
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Ray White
Joined: 02 Dec 2014 Posts: 6304 Location: Derby
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Posted: Sun Aug 25, 2019 12:37 pm Post subject: |
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As it happens, a relay came with the Dynamater.
I haven't yet read all the blurb but will be more cautious having read about your experiences with one of these things! |
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