Wiring question

[Garym]

Hi all.I am in the process of restoring one minor from two,replacing a rotten bodyshell for a good one.
The wiring harness is in place on the good one,done before I bought it.It looks like someone has replaced the dynamo for an alternator,because the leads to the regulator box are taped up and bypassed.Does anyone know what leads go where, and will any alternator fit, or just certain ones.

[bmcecosse]

Virtually any alternator will fit - unless you have a strange foreign one maybe ? Most alternators these days are completely self contained (the old Lucas 11AC had external control box and relay) - they require a good thick wire directly from the main 12v +ve bus (usually taken from the live side of the starter solenoid) and they need a feed from the Ign warning light which acts as the sensor wire, and also tells you if the thing is charging! And of course - they virtually all need to be on a -ve earth car.
The main feed wire would normally be BROWN - and connects to the large terminal on the alternator, and the sensor wire would be the brown/yellow wire which originally was connected to the D terminal on the regulator - and then to the field connection on the old dynamo. Just remove the two wires from the D terminal - and join them together - and connect to the small terminal on the alternator.

[rayofleamington]

The wire from the big terminal (the main power feed) needs to be capable to take the maximum Alternator current.
So if you fit a 60Amp alternator, don't forget you need wire that'll take 60 amps.

I had one Minor where the previous owner had wired up the alternator with speaker wire. This caused no problems because the car had standard kit (no heated window etc..). The current will match what is needed plus some more to charge the battery.
However when I got a flat battery I was in a panick - this would potentially allow the max Alternator current, which could have set the tiny wire on fire. At this point I remembered why I had planned to replace that wiring ASAP!

On the same Minor I re-wired the entire back end as it had been made up like a birds nest with short pieces of wire twisted together at the ends. I lent the Minor to a friend for a year and not long afterwards one of the engine bay wires caught fire (horn or indicator - I can't totally remember).

Another example: On a Landrover I had once, the previous owner had wired a 12v socket in the back of the cab. He'd fitted the fuse at the socket, so if the feed wire sheathing got damaged on any of the sharp drilled holes he made, it would simply have overheated and caught fire.
This is not really meant to scare - but just a warning about avoiding wiring looms that have been modified by a previous owner - in many cases they have made a real mess!

Almost always the best thing to do with a modified loom is to replace the entire thing. But failing that, take out ALL the mods then fix anything that doesn't work using properly fused feeds!