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David Gore
Moderator
Username: david_gore

Post Number: 3306
Registered: 4-2003
Posted on Sunday, 19 May, 2019 - 09:14:   Edit PostDelete PostView Post/Check IP

My long-time US friend who is also a motor bike enthusiast has sent me a link to an article that included a summary of the post-WW2 British automotive wiring code. I have reformatted this information to make it easier to follow:

"The British wiring codes are amazingly simple and easy to learn.

Black is ground.

Brown is power - After it is switched in the ignition switch, Brown becomes white.

When White is fused, it becomes green and when Brown is fused, it becomes purple

When Brown goes through the headlamp circuits, it comes out as Red with Green stripes for parking lights which usually go through the fuse block and comes out red to go to the lamps and red with a white stripe to go to the dash lights. Brown comes out of the head lamp switch as blue for head lamp dip switch, blue with white stripes for main beam and blue with red stripes for dipped beams.

Any wire that has a black stripe is a typically a switched circuit ground (like a lot of negative side two wire horn systems) and green wires tend to feed the convenience things on the car. The yellow wires are for the alternator or generator. There are more, but armed with this info you can troubleshoot almost any system on a British car.

Grounds are the big problem, keep them clean and assemble them with silicone dielectric grease. The little bullet connectors throughout the car need to be likewise cleaned and assembled with dielectric grease, and check to make sure the heat hasnít overcome the springback of the metal for the secure connections.

Some of the weaker contacts in the switching can greatly benefit from having a simple 12 volt relay placed in the circuit to take the electrical load and heat off the switches.

Although early British cars typically have two fuses for the entire car and the later ones have four (up to the early eighties); the electrical systems if properly cared for and kept in good order are almost bullet proof."

.
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Larry Kavanagh
Grand Master
Username: shadow_11

Post Number: 447
Registered: 05-2016
Posted on Saturday, 25 May, 2019 - 23:45:   Edit PostDelete PostView Post/Check IP

Thanks David, for me (who knows little or nothing about electrical circuits) this is invaluable information.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 2849
Registered: 06-2009
Posted on Sunday, 26 May, 2019 - 04:02:   Edit PostDelete PostView Post/Check IP

David,

This little nugget deserves its place alongside the eBay auction by Craig Bolton for Lucas Replacement Wiring Harness Smoke Kit.

I actually had him repair my now sold '99 Jag XJ8L when the fuel pump decided to die when I was driving through Belington, WV. It was an interesting weekend.

Brian
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David Gore
Moderator
Username: david_gore

Post Number: 3315
Registered: 04-2003
Posted on Sunday, 26 May, 2019 - 09:18:   Edit PostDelete PostView Post/Check IP

Brian,

I was considering putting this information in the previous thread detailing the world's humorous opinions on Lucas electrics.

I decided agains doing this and opened this thread as I could only see benefits coming from this knowledge.

However, there is still a nagging thought that the colour code is an example of making a simple thing complicated.......

.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 2850
Registered: 06-2009
Posted on Sunday, 26 May, 2019 - 10:38:   Edit PostDelete PostView Post/Check IP

David,

If that information was not actually intended as a joke, it comes across as such anyway because it is just so ludicrous and Rube Goldbergian. The line, "the electrical systems if properly cared for and kept in good order are almost bullet proof," would have any lovers of British marques ROTFLTAO.

I have never heard any serious devotee of all things British automotive utter such a thing other than as the most arch of humorous observations.

Brian
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 2851
Registered: 06-2009
Posted on Monday, 27 May, 2019 - 01:04:   Edit PostDelete PostView Post/Check IP

By the way, the following applies not only to the Haynes instructions, but to large parts of any workshop manual as well.

The REAL meaning of the Haynes instructions
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Mark Aldridge
Grand Master
Username: mark_aldridge

Post Number: 611
Registered: 10-2008
Posted on Monday, 27 May, 2019 - 05:29:   Edit PostDelete PostView Post/Check IP

Brian, have you experience of old Bosch electrics, in particular wiring ? 924 Porche, 190e, W123 X2, W124 Mercedes. They really are no better than the Prince of Darkness in old age.
Mark
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Larry Kavanagh
Grand Master
Username: shadow_11

Post Number: 449
Registered: 05-2016
Posted on Monday, 27 May, 2019 - 08:49:   Edit PostDelete PostView Post/Check IP

Definitely Mark, the engine wiring loom on the W124 Merc between 1993 & 1997 was a disaster. Someone came up with the bright idea of using biodegradable wire coating but due to the heat generated in the engine bay it degraded long before its time causing serious engine management problems and a possible fire hazard. I had to replace one recently and it wasn't cheap.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 2852
Registered: 06-2009
Posted on Monday, 27 May, 2019 - 13:12:   Edit PostDelete PostView Post/Check IP

No, I don't have that experience. That being said, no one, least of all me, has made the claim that non-British marques don't have their quirks and issues, too.

This is particularly true in the early stages of new (at the time) technology.

Brian
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Mike Thompson
Frequent User
Username: vroomrr

Post Number: 554
Registered: 04-2019
Posted on Sunday, 02 June, 2019 - 01:23:   Edit PostDelete PostView Post/Check IP

Why does the engine have so many grounds on it. I know of 3 major grounding cables to the engine. (I'd make a joke at this point, but we loose people, so I won't.)
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Robert J. Sprauer
Grand Master
Username: wraithman

Post Number: 436
Registered: 11-2017
Posted on Sunday, 02 June, 2019 - 02:05:   Edit PostDelete PostView Post/Check IP

The engine is isolated from the subframe and the subframe from the body. RR uses positive electrical flow and relays the grounds for circuit continuation.
Therefor it is important that grounding is clean and connected.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 2857
Registered: 06-2009
Posted on Sunday, 02 June, 2019 - 03:42:   Edit PostDelete PostView Post/Check IP

It's the "clean and connected" part that's far more critical than the number, and it seems that both "clean" and "securely connected" is a perennial problem on many British marques.

I can't count the number of issues I've fixed by doing nothing more than disconnecting grounds, cleaning the terminals on both sides of the connection, giving both a good coat with Sanchem's NoOxId A-Special electrically conductive grease, and putting them back together. I now swear by using electrically conductive grease, as it lasts "forever" and prevents corrosion and the ingress of dirt (where that counts - at the point of contact).

Any time I pull apart any electrical connection I mechanically clean what I can reach that way, chemically clean what I can't (e.g., Caig Deoxit or TV Tuner cleaner & lubricant) and give the terminals I can reach a very thin coating of electrically conductive grease. I have never had to revisit one that I've treated in this way.

Brian
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Robert J. Sprauer
Grand Master
Username: wraithman

Post Number: 437
Registered: 11-2017
Posted on Sunday, 02 June, 2019 - 04:20:   Edit PostDelete PostView Post/Check IP

I use the same protocol Brian.

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