Is the alternator fubard?

brianmm · Two Stroke Sniffer Joined: 01 Sep 2010 Karma :

Hi gang,I have an old 91 xj600,Last of the pre-diversions.A couple of weeks ago i had to replace coils and rectifier/regulator,It was pushing out 18 volts.Run fine until the weekend and the battery went flat,now the voltage output is sitting at 11.5 volts and it doesn`t rise with revs at all,Could this be the rectifier again or more likely the alternator?All help greatly appreciated.

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

The alternator is probably ok as is the new regulator - immediate suspect would be the battery was stuffed by the broken regulator. If you can substitute the battery with another one (even a car battery using jump leads) and see what happens.

f.

brianmm · Two Stroke Sniffer Joined: 01 Sep 2010 Karma :

That thought had crossed my mind m8,but it was just with the meter on the terminals the voltage is not rising with the revs,even f the battery doesn`t accept it the output with the engine running should be higher than 11.5 should it not?

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

18 volts is too high I think. New reg/rec and battery I think.
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brianmm · Two Stroke Sniffer Joined: 01 Sep 2010 Karma :

I think i may have got away with the battery,I replaced the regulator about two weeks ago and it has run ok since then,holding a charge no problem.When i discovered this morning that the battery was low i checked the output from the replacement reg and it was only showing 11.5v.i stuck the battery on a charge and it charged fine and seems to be holding it.

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

No, really, it won't. It'll run out of grunt and the voltage will drop, which is why when you stick your busted battery on a more powerful mains charger it seem to charge and will start your bike. Then it'll be knackered again in two days and you have to push it home in the rain.

f.

brianmm · Two Stroke Sniffer Joined: 01 Sep 2010 Karma :

Ok in the morning i will attach a known good car battery with jump leads to it and see what sort of reading i get,hopefully it will just be the battery and t will give me an excuse to try one of these new gel things lol.

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

Make sure you disconnect the bike's battery when you do (just disconnect the earth strap from it) - it is is knackered it'll have a go at pulling the car battery voltage down as well. Hopefully a quick resolution after that.

f.