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Alternator Not Charging


dandanfireman

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Hey guys,

 

I'm in the middle of getting my S7 on the road again and have now found the alternator doesn't seem to be charging. Its a standard pinto one. I have removed the rear casing to check the brushes and they appear fine however the battery stays at 12v and drops without raising up to 14v ever.

 

There is a 2.2 mF capacitor on the rear aswell which is linked inline with the earthing part of the circuit, are these known to fail at all?

 

Any advice on what could be the issue would be greatly appreciated.

 

Many thanks

 

Daniel Hall

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options are new or have the one you got reconditioned but in mo new is same price as recon when I priced it up. but the lads at my local parts place found me an old stock item and got it cheaper than should of been hth

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Sound like a Lucas (Ford) A series with a radio supressing capacitor. This should be connected to its own solo terminal and earths through the body of the alternator. There isn't usually an actual earth wire. If you don't have a radio you don't need this capacitor and it can be removed without problems

The main connector has two large spades which are common for output to battery + and a third small spade which is for the excitor wire to the slip rings and comes from one side of the ignition light. Other side of ignition light comes from an ignition live. Make sure the excitor wire is live at the alternator end when ignition is on. Without this you get nothing out of the alternator.

Is there a good engine to chassis to battery neg earth.

 

Nigel

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Guest chris brown

Does the ignition warning light come on when ignition is switched on and go out when the engine is running? Without this light working it is not unknown for the alternator not to work (some do but other identical ones wont)

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Yes, with the ignition on. Check with the ignition on the ignition light should be off if that terminal is disconnected. Ignition light should come on if that terminal is earthed. That would confirm the excitor wire is wired correctly.

 

Nigel

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Guest peter2b2002

you could alwas check the leads where they connect to the alternator minty had a problem a few years ago when we went to le mans lost the chargeing light thurned out the wires had brocken inside the insulation by the studs

peter2b

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Ok many thanks guy i now know from yr comments I have wired the gen light and red light on the dash incorrectly. Also the reason the alternator wasn't charging the battery was because I had put in an old smiths ammeter and wired it up according to the caerbont website however my ammeter was different. Either way the alternator is charging now thanks guys.

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  • 2 months later...

okay after checking over and over it turns out my excitor wire isn't ttached at all. I found it lying loose under the scuttle panel. Longboarder you mentioned this should be attached to the ignition light? Is this excitor wire used as an earth for that light or a +ve ? I'm a little confused how this wire is used. Does it require a 12v supply or does it supply one itself. Don't think i should become an electrician lol

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