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two wire alternator
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Tue May 15, 2018 11:35 am    Post subject: two wire alternator Reply with quote

This is a bit of borderline classic question...but I'm a bit lost on alternators. I have a '97 Jaguar that's not charging. It has a connector on the back with three terminals ( in addition to the main output post ) ...the plug that goes into it has two! wires. Why two ..and what do they do? I assume one is an exciter voltage from the ignition? ..what's the other one?
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'60 Armstrong Siddeley Star Sapphire
'80 Reliant Scimitar
'47 Jaguar MKIV --- in bits!!!!
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47Jag



Joined: 26 Jun 2008
Posts: 1480
Location: Bothwell, Scotland

PostPosted: Tue May 15, 2018 12:28 pm    Post subject: Reply with quote

Ignition warning light perhaps?

Art


Last edited by 47Jag on Tue May 15, 2018 7:31 pm; edited 1 time in total
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petelang



Joined: 21 May 2009
Posts: 442
Location: Nottingham

PostPosted: Tue May 15, 2018 2:53 pm    Post subject: Reply with quote

You need to identify the colours of the cables to be sure but probably the regulator within has "battery sensing" and this means there is a thin wire connected back to the battery terminal (or very near) to tell the regulator what the actual voltage is at the battery terminal. This was done to overcome long cable lengths and high under bonnet temperatures where volt drop could occur and hence the alternator was getting false information leading to either overcharging or undercharging.
The second wire would be brown with a colour tracer or just plain brown. The ignition "exciter" from the warning light conventionally brown and yellow.
The above is if it is a Lucas ACR type with integral regulator.
Some Jaguar models also had a fan mounted to the battery case to assist cooling the battery as they got very hot under the bonnet and this similarly affected accurate charging. In these cases there may be a further wire from the alternator to power the fan.
Peter
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Wed May 16, 2018 11:01 am    Post subject: Reply with quote

I've picked up info ...the two wires are a seperate ecxiter feed which arrives at the alternator via a torturous route that also splits after a fuse and supplies a bunch of ancilliaries...which strikes me as poor design, so there's maybe fuse away OR the connector that supplies the exciter votlage to the fuse box is, incredibly, under the wash wipe bottle right at the front of the car...so that may simply be corroded. There's a very good thread on the Jaguarforums about it..I'll let you know!
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'80 Reliant Scimitar
'47 Jaguar MKIV --- in bits!!!!
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