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MG MGB Technical - Lucas Gremlin Got Me SpOOked

Greetings --

Twice in the past six months my '64 electrcal system has shut down -- once while parked and the other just driving along.

It appears to be an ignition switch problem, so I ask for various expertize.

When this has happened, there is no ignition light, no fuel pump, no starter -- fuses have not blown, and no electric smoke, (as in short circut) -- it is as though the battery is disconected. After about five minutes, all is back to normal operation.

There's no outstanding electro/mechanical connection problems --eg: all connectors are relativley new, as is the fuse block.

My general question is this a sign of ignition switch failure? Any one experience a similar situation? Any other thoughts or suggestions?

Thanks --- glg
glg

glg. I would tend to agree with your diagnosis. It is either the ignition switch or the brown wire going to it that is bad. I would check the wire and its connectors first, then the switch. But, I believe you have hit it on the head. Les
Les Bengtson

Does anything else that is not connected to the ignition switch work, such as lights? If everything is dead then it could be a poor battery connection. I have had the battery ground to the chasis come looose enough to cause an intermitant total electrical failure. Problem could be a loose hot wire too. Could also be the link wire between the batteries if you are still running twin 6 volts.

-Jared
Jared Snider

If the battery became disconnected while driving along the alternator would continue supplying power and the engine would continue to run - but you may get an overvoltage condition and blow any lights that are on.

Like Jared syas if the lights don't work either then you can forget the ignition switch, I would check the cleanliness and tightness of the connections at the solenoid.
Paul Hunt

Les,

Thanks for concurring with that assesment. Since it's only been twice this summer, it's impossible to track down until it happens again.

I shall double check connections and to play it safe, will carry a spare ignition AND headlight switch -- (ignition on for parking lights and engage starter with headlight)

Perhaps just a fluke with no answer.

Paul and Jared -- It's that the stuff mentioned -- and the horn -- would't work -- then, after a few minutes all was well --- is that a sign of impending switch failure?
(battery connections solid and clean )

Just don't know. Thanks for your replys

glg
glg

GLG,
Good luck on your gremlin, it looks like the most obvious culprits have been identified. Just an unrelated tip, though, you may want to install a 30 amp fusible link between the large brown wire and the solenoid. Years ago I turned on the headlights on my '64 and, due to a short, burned up my entire wiring harness before I could raise the bonnet and disconnect the brown wire. I've run one since then on my early B's. I use one of the pink, u-shaped fuses with a clear window in the top. Not sure of the application, but just about every Japanese car in the junkyard uses them.
David
David

30amp Spade fuses you mean David? or the computers main protection relay? They start off as a red color but fade over time from heat to a pinkish color before they usually blow on the older jap cars that is.
CJD Dark

Thanks for the tip David.

During the restoration I had thought of putting in a multiple fuse block -- a chicken in ever pot and a fuse in every circut.

Sometimes Lucas is just facinating!

glg
glg

glg - if the horn (what about the lights?) didn't work until the car came back to life then I say again it isn't the ignition switch but a bad connection, probably at the solenoid. On a 64 these are probably spade connections which

If considering main circuit fuses alternator equipped cars really need two - one in the alternator brown(s) and one in the other brown(s) feeding the remainder of the cars electrics where they come off the solenoid. 30 amps is OK for a dynamo but they would need to be rated *at least* to the maximum output of an alternator i.e. 34 amps for early cars increasing to 43 amps for the 18ACR. Whilst the fusing current is generally higher than the rated current running a fuse at higher than its rated current will shorten its life.
Paul Hunt

CJD,
The fuse that I use is not a spade fuse, but has two parallel female connectors that plug in to a fuse block on the Japanese cars and is pink from new. It very well may be the main computer protection, I don't know. They are on the rack at every auto parts store, though, and are are about 1/2"x 1/2" square on the top. I use a double-ended male connector that joins the brown wire and one terminal on the fuse and the other fuse terminal slides over the spade connector on the solenoid. No cuttings or splicing is necessary.
David
David

This thread was discussed between 02/11/2003 and 04/11/2003

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