The common belief is that British wiring is unreliable and troublesome. Few TVR owners would disagree with that statement and the cult of “The Fallibility of Lucas” has become so common that even people who have never owned a British car (but are car lovers) make “Prince of Darkness” jokes. And we laugh...... Did you hear what the Lucas Works Motto is? “A good days work and home before dark!”

Please send me your Lucas jokes – I'll post them on the web site!

Automobile wiring is not rocket science and there are some things we can do to make wiring and electrics in general more reliable. Even British cars can have reliable electrics. I rewired my 2500M and have had NO electrical problems for two years. None! So how do we make our TVRs electrically reliable and why do they fail?

Have you ever seen a 1929 Ford Model A wiring diagram? Probably not. The wires on Model As are cloth covered and there are very few wires. Their connections are “bullet” connections where there is a male part on each end of the wire and a dual female connector that each male part plugs into to connect wires. They look almost exactly like the infamous “lucar” connectors that all TVRs up to the Tasmin/280i series used. They (on the old Fords) seem never to have problems. Most of the problems we have with British wiring are in the connections – usually multiple connectors where 3 or more wires come together. The Lucar female connections (called “Snap Connector Sleeves”) are open on the ends and if there are an uneven number of wires connecting, leaving an open end to the sleeve, they let in air, water, oil, gasoline, fumes, etc. One theory of Lucas wiring would tell us that they let out smoke, which is needed to conduct electricity. There is no engineering explanation of that theory!

The “Snap” is important. Most connection problems are due to corrosion (as explained above) or loose connections. The male “bullet” connectors must “snap” into place in the female “Snap Connector Sleeves”. If they don't, they will pull or fall out. This is the first thing to fix on any wiring harness. There is a special tool (available from British Wiring – see the end of the article for their web address) that pushes the bullets into their Sleeves. It is essential.

Bullets need to be connected to the wire very carefully. I solder all of mine, but there are special crimping tools that work well also. If you check factory wiring harnesses, the bullets are crimped. But without the special crimper, the connection will not be good enough.

Since good connections are important, what makes bad connections? Corrosion as well as loose connections can be at fault. If a connector moves (isn't “Snapped” in place), the corrosives (air, water, etc) can get to the whole connection surface and make it less or non conductive. Have you noticed that connections that have been securely in place for years don't cause problems? The corrosion can't get between where the connectors are securely in contact. However, don't plug a new bullet connector into an old multiple sleeve style connector – it is inviting trouble – the inside of the sleeve might already be corroded. This is also why an “easy disconnect” plug is a good idea for our M series bonnets. If you are always unplugging the wires that go to the bonnet the connectors will wear and get loose, allowing corrosion to get into the sleeves.

Automakers have tried other types of connections. Multiple connectors like the ones on the Tasmin/280i series are meant to be better sealed than the Lucar Bullets. Are they? I found on my 280is that they are just as bad, but do stay together better. In fact, they are hard to get apart. Automakers have also added insulating grease to the connectors. The theory is that you coat the connectors and when they connect they scrape off the grease and make good contact but are still surrounded by grease. Sounds good! But if there is any corrosion (and probably even if there isn't) connectors get hot and melt the grease. It flows away or even into the connection if it is moving at all and soon causes problems. I know of a Dodge (made in Normal, Illinois at the Diamond Start plant) that has so much grease in the relay connections that every few months the relays stop working and the connectors have to have the grease cleaned out of them! I'd rather have a bullet connection!

The best connection is no connection. Try not to add any type of connector and if wiring something new, make the wires as long as needed in one piece. Wires don't usually cause problems, but the connections on the ends do.

Wiring Diagrams

The British have a wiring code from before WWII. Their wiring code suggests that all cars made in the UK use the same colors of wire to indicate what each wire is used for. Of course we TVR owners know that is not always used – the first Tasmins had all black wires with tags on the ends telling what the wires did. Of course the tags fell off.......

There is a web site on British Wiring Codes at http://www.jcna.com/library/tech/tech0014.html. It is pretty good, but remember, TVR didn't always follow it. While not all British cars use these codes, most do. When I rewired my 2500M I mostly followed this code. It was usually the same as the old wiring harness, but not always. I followed the code anyway. I suggest you do also.

British wiring has a base color and a trace color.

The color codes are: Color Code Color Code White W Black B Red R Green G Yellow Y Orange O Brown N Blue U Slate (gray) S Purple P So the code for a red wire is “R” and for a blue wire with red tracer it is “UR”

There are some general use rules that should be followed: Grounds are solid Black Ignition circuits have a base color of white Circuits controlled by the ignition switch have a base color of green Circuits that are hot with the ignition switch off have a base color of purple Headlight circuits have a base color of blue Running lights have a base color of red Brown is the main battery feed. Each of the individual items in the above basic circuits have a different trace color.

Wiring diagrams used to be in the owners' manual of every car. Of course they took up ¼ of a page! I knew things were changing when I looked at my 1971 VW Super Beetle wiring diagram in 1973 – 3 pages and the ground wire was orange! Since then the wiring diagrams have gotten much more difficult to decipher. The unreadable 2500M wiring diagram is 2 pages (shrunk to 1 making it unreadable). You need 5 or 6 pages for a 280i and all the books show you several of each page to pick from with no accurate indication as to which one is yours.

There are about 3 wiring diagrams for 2500Ms that are circulating. I think they all came from the “factory” code that was xeroxed and reduced to the point where it is useless. The wires simply can't be followed. I also got one off the Internet and it was not accurate for my car and one from a vendor that again wasn't accurate for my car. So I decided to make my own. The file “Stock2500MWires.pdf” is a main wiring diagram for a stock 2500M. Is it correct? Probably. Remember, each car is different. They are hand made! If you have corrections to be made to them, let me know! (email me at farquasi@mac.com) Some of them I had to guess what the wires were supposed to do since the factory wiring diagram was so bad. There are some things not on my wiring diagram – most notably the seat belt interlock wiring and emission wiring.

Note that there are only 6 fuses (4 in the fuse box) and some substantial users of current are not fused at all! So I decided to rewire my 2500M and improve on the old wiring harness. I used 18 fuses and fused everything. I used a “blade type” fusebox with 16 fuses (available from British Wiring – see below) and mounted it on the top of the driver's footwell. That necessitated moving the wiring cable from the right to the left side of the engine. I also used more relays for the cooling fans and horns. There are two inline fuses (not counting the radio) also. Finally, I doubled the wiring to headlights and cooling fans just to make sure they never failed. Rather like suspenders and a belt, but I hate to lose lights and I really need engine cooling. See my revised wiring diagram in the file “”Mod2500MWires.pdf . Again, these files are in the members only section of the TVRCCNA web site.

What wire to use?

British wire and US wire is not rated the same way (of course). US is by gauge – the larger the gauge number the smaller the diameter of the wire and the less current it can carry. British wire is rated by the number of 0.3 mm diameter strands in a wire.

British Wire Size (Strands)	Capacity (amps)	Use
9	5.75	Side & tail lamps
14	8	General Wiring
28	17.5	Horns, Headlights, High Current accs.
44	25.5	Generator, Control Box, Ammeter
65	35	Alternator feed, Ammeter
84	42	Alternator feed, Ammeter
120	60	Alternator feed, Ammeter

If you can find the US wire in the right colors there is nothing wrong with using it unless you are looking for a Concours deElegance win. If you are soldering the bullets on there should be no problem.

Most Common British Wire Sizes	US Wire Sizes (Approx)
14 strand	18 gauge
28 strand	14 gauge
44 strand	12 gauge
65 strand	10 gauge

Make sure you use large enough wire. Hot, melting insulation doesn't help the reliability of your car!

The covering (insulation) around the wire is important. It keeps the wire from corroding. You don't want nicks in the insulation so that the copper is exposed. Copper conducts electricity very well, but if it is exposed to air it oxidizes to form bluish – greenish copper oxides which DO NOT conduct electricity! If you find a wire showing dull, blue-green colors on the wire you might want to replace the wire. Sometimes I have found corroded wires inside the insulation. I don't know how it got there, but I replaced it.

Solder contains lead (newer solder doesn't ), silver, tin, and other metals. The idea is that the solder doesn't corrode. It does. However, it doesn't matter if the connector was not corroded when it was soldered. Only the surface of the solder corrodes where it is exposed to air. Much of solder is tin, which doesn't corrode very much. But tin doesn't conduct electricity that well, so it needs other metals alloyed with it. Most connectors are “tinned” -- that is coated with tin or solder so they corrode less and when you solder to them they make a good contact. When you solder something to a tinned connector the oxidation-covered solder melts and the oxidation goes away.

Getting good materials:

There is no way to use cheap wiring supplies to make a good wiring harness. It costs money. There are many places you can get good wiring supplies, but most of them are focused on hotrods – a bad word in the British Car groups. British Wiring has the right tools and materials. A quality crimper is important as is the tool to snap bullets into the sleeves. A good soldering iron is important also. A quality “gun style” soldering iron is very helpful. Get the big one. You'll need it.

You can get a wiring harness for the 2500M from British Wiring. I ordered it and it was very nice. It just didn't fit my car. The wires came out at different places and were different colors. As I said... each car is different. I figured out what colors and amounts I needed and sent for them and the connectors. It cost as much or more than the wiring harness. But it fit.

Sources of Materials and Information:

British Wiring at http://www.britishwiring.com has wire, connections, information, and lots of other stuff in their catalog. You can download the catalog from their site. It is like a textbook on wiring British cars. From this company you can get relays, the tools, bullet ends and snap connectors.

The Jaguar Clubs of North America have a web page with the British Wiring codes at http://www.jcna.com/library/tech/tech0014.html.

British wiring is summarized at http://www3.sympatico.ca/peter.mckercher/restoration/wiring.html.

 

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