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MG MGB Technical - Alternator wiring

Inadvertantly placed on General List, now transferred:

Hello good people,

I am sure someone will be able to assist here. I have a 18ACR Alternator on my B Roadster. My wiring loom only has one thick brown wire and one thinner brown/yellow wire. I know that the thick brown wire goes to the starter solenoid and the thinner brown/yellow wire is the charging light wire. There is provission for a further large wire on the Alt' connector. I have read that both these large spade connectors should have thick brown wires and both should go to the starter solenoid. Am I giving myself a problem using only one brown wire to the starter solenoid?

Thank you for your time.

Andy Shepherd. Newcastle. UK

M A Shepherd

My understanding is that the designers of our cars felt that it was adequete to use on a single brown wire from one of the large spades back to the battery via the solenoid connection. Probably, they were right.

I have advocated using a second, simply because it cannot hurt, does no harm, and might actually reduce the load on either wire (if they are both of the same gauge, # 10 awg.), allowing perhaps a slightly greater and easier flow back to the battery for charging AND to the various circuits and current drawing items in the car. All things considered, it would then probably make as much sense to increase the gauge of the Brown wire from the solenoid to the fuse block as well to something like #8 awg, maybe even #6 awg. just to ensure that those electrons don't choke on the single # 10 ga. wire in the OE loom. What is the point of providing an easier path to the battery without also increasing the ease of access to those electrons by the rest of the electrical equipment in used by the car?? Just an alternative way of looking at our cars electrical system and its "efficiency".
Bob Muenchausen

Some years had a thin brown wire as well as the thick but they both went to the same place on the solenoid, then we got the so-called two-wire alts which are actually three-wire but with only one of the output spades used as you describe, then in the latter years when the alt capacity went up two heavy gauge output wires were used.

As Les says there is no harm in providing one (I have used the spare terminal to connect direct to the fan relay on my factory V8 and get a useful boost in cooling) but unless you have added significant electrical load to the car there probably isn't much to gain.
Paul Hunt

Thanks Bob & Paul
You have answered my query. I have added an electric fan but I have fed this through an additional fuse and a relay likewise spot and fog lamps. Everything else as standard. I think I will put the extra cable to the alternator though.
Many thanks
Andy
andy shepherd

This thread was discussed between 17/11/2002 and 18/11/2002

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