Old wiring, new Bosch alternator

andyborris Posted a lot Freedom is just another word for nothing left to lose. Posts: 2,218	Old wiring, new Bosch alternator andyborris @andyborris
	Sept 25, 2012 18:10:07 GMT Select Post Deselect Post Link to Post Back to Top
	Old wiring, new Bosch alternator, how to connect the two? My wiring is a mess, but not quite as bad as I first thought! Car now has a 2 wire Bosch alternator (instead of an dynamo), with a large cable running to the battery and a second much thinner wire, this is (I'm assuming!) the field wire? Can I use this field wire to power the ignition light? Secondly, on a Triumph a wire from the dynamo control box provides power (via the ammeter) for the circuits not controlled by the ignition switch. In fact all the non-switched current goes through the ammeter! How can I use this wire to maintain supply to these circuits and get a true ammeter reading? Will the ammeter work if take a feed from the charge wire on the alternator? Thanks


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ianboyd Part of things Posts: 592	Old wiring, new Bosch alternator ianboyd @ianboydsnr
	Sept 25, 2012 18:59:05 GMT Select Post Deselect Post Link to Post Back to Top
	The thin wire doesn't power the light, the battery does, the thin wire excites the alternator and earths through it, therefore the light goes on, when the alternator is running,that same wire becomes a live, that extinguishes the light, But it does go to the light non the less, big wire to battery, little wire to lamp, make sure the alternator is well earthed to the engine, and the earth strap is good, ammeter should be wired the same as before, only you need to connect the control box to the battery, through a fuse, effectively the control box becomes a junction box! Bear in mind that the alternator will produce more power, so will need thicker cable!
	Last Edit: Sept 25, 2012 19:02:23 GMT by ianboyd

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andyborris Posted a lot Freedom is just another word for nothing left to lose. Posts: 2,218	Old wiring, new Bosch alternator andyborris @andyborris
	Sept 25, 2012 19:26:08 GMT Select Post Deselect Post Link to Post Back to Top
	Sept 25, 2012 18:59:05 GMT ianboyd said: , ammeter should be wired the same as before, only you need to connect the control box to the battery, through a fuse, effectively the control box becomes a junction box! Should have added, dynamo control has long gone, some of the control boe wires were joined together by nicely hand cut oblong copper strips!


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Clamity South East Posts: 708	Old wiring, new Bosch alternator Clamity @calamity
	Sept 26, 2012 14:51:52 GMT Select Post Deselect Post Link to Post Back to Top
	Sept 25, 2012 18:59:05 GMT ianboyd said: Bear in mind that the alternator will produce more power, so will need thicker cable! This means it's a good idea to fuse the thick wire at the battery end with e.g. an 80A fuse. Unless you really want to keep it, it'll save you two long runs of thick cable and likely some grief if you get rid of the ammeter and just run the thick wire direct from alternator to battery. The ignition light will tell you if there's any problems in the charging circuit. (Either it won't light up when you turn the key indicating an open circuit/fried alternator, or else it'll come on when the engine runs indicating the belt has gone.)
	~ '72 Toyota Hiace ~ Sweet chestnut shed build ~

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