Extra Alternator Cable

[Stagnation]

I am reviving my Stag which has been off the road for about 10 years. I had to get a new alternator so ordered the usual model, but when it came it appears my Stag has an extra brown cable which connected to the old alternator via a spade connector which is positioned about an inch up from the ordinary plug-in bank of connectors. I can't seem to work out what it is for (mine is a Ford V6 conversion). It doesn't look like an add on cable. Any ideas? The engine runs without it and every piece of electrical equipmentI've tried still works?

[DJT]

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This cable is the 'excitation' connection for theoriginal alternator. Some aftermarket 'will-fit' alternators don't need it, but the voltmeter may not show correct readings without it, as I recently discovered.

There should be a permanent 12v at this lead, so if there is nowhere on the alternator to connect it, and everything works OK, then tape it up to prevent shorting.

Dave

[GDPR]

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Sorry to correct Dave, but the brown yellow is the excitation lead - the "spare" thin brown is the sensing lead for battery sensed alternators.....

Russ:dude:

[DJT]

imported post

kryten wrote:

Sorry to correct Dave, but the brown yellow is the excitation lead - the "spare" thin brown is the sensing lead for battery sensed alternators.....

Russ:dude:

As soon as I pressed the 'send' button, my thought was 'Not sure about this, but Russ will be along soon to correct me'. You are, of course, right about about the brown/yellow wire, Russ.

(Memo to self. 'Don't try and help with electrickery, when it ain't your subject' )

As I stated, I have just been through a similar problem. My car is a late '73 build. The mounting screws are in place for the alternator charging relay and control box, but I am not sure if they were originally fitted or not. Down on the chassis leg below thep/steering pumpis a black, in-line, Lucarconnector fortwo large brown wires from the alternator block, plus a white connector for two smaller wires. One of these goes to the alternator block and the other was hanging spare. This is the one that has +12v. I recently had charging problems and changed the battery as it was 10 years old. This didn't fix the problem, so I went to our local auto-electrical Stag guru who advised me that not only was the alternator very old, but it was the wrong type - only 35amp and no connection for this additional wire.

Fitted a refurbished, original-type alternator. Connected up the 'spare' wire and all is now fine, with well over 13-volts showing no matter what load is on the system (lights, heater, indicators, wipers, rear fogs, radio all together make no difference).

Does this sound as if this is a Stag that has been converted from early to late type alternator?

Dave