Wiring Do’s & Don’ts

heater fan plug

What’s wrong with this picture ?

Over the years much loud noise has been generated about the supposed deficencies of Lucas electrical systems, mostly passed along by the ignorant to the ill informed.  To this Jackals’ Chorus I would pose this simple question:  Please name even one Japanese car with its 50 year old electrical system still intact and working?   O.K.  I thought not.

There are some simple rules for understanding Lucas wiring (it also helps if you’re not color blind).

So here are the basics:

E-type in trailer

Mike & Butch tie down an E-type

Black is Ground   A.K.A. “Earth”, Letter “B”

Brown is Battery,   Hot all the time,  Letter “N”

White is Ignition  (also electric fuel pumps),  Letter “W”

Green is Switched thru the Ignition & Fused,  Letter “G”

Blue is the Headlight circuit, Letter “U”

another view

Almost tied down

Red is the Parking Light circuit, Letter “R”

A green wire might have a black stripe if it goes to the temperature or fuel sending unit, but green with white is RIGHT, and green with red is the left turn signal.

Now we’re ready to address the question posited by the first picture.  Green wires in a 4-way snap connector common with black wires is a dead short, but not to worry because it’s fused, and this raises another point.  A 17/35 amp fuse is a ‘slow blow’ fuse.  It handles 17 amps continuously and will accomodate a temporary 35 amp surge, such as when you turn  the heater fan on when the wipers are working.    Replace it with a 35 amp Buss fuse and it becomes a meltdown.  However no worries either way here, because the heater switch didn’t work anyway !

B.T.W. : That yellow band around the oil gauge hose means it’s an original Smith’s hose, and that means this one is at least 40 years old.    Best to replace ’em when you see that, because over time they get very brittle and once they crack from the engine flexing you can lose five quarts of oil in just a minute or two.


broken synchro ring

Broken baulk ring

Here’s the broken baulk ring which Patrick fished out of the four synchro transmission of his MGB GT last week.  It’s split is just slightly to the right of the top ear of the baulk ring (click on the picture for a closer look).  It’s an unusual event when anything breaks in one of these transmissions, but there you have it.  At last report the car and its owner were in Texas headed for Arizona, after stopping in Tennessee to replace the fuel pump.  Best to carry a spare !

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