will4x4 Posted July 22, 2010 Share Posted July 22, 2010 Hi my 1994 defender battery light has just come on after driving 40 odd miles. I have a voltmeter and it is still reading 13.5 when the engine is on and 12 when off... My batteries are both about 12 months old and seem really good (their the maxim type or whatever there called) Any ideas where to start looking and why it would come on when all seems fine and dandy? Cheers Quote Link to comment Share on other sites More sharing options...
western Posted July 22, 2010 Share Posted July 22, 2010 check the drive belt first -- is it intact & tight are the battery connections clean & tight could be a charging fault with the alternator, worth having it bench tested. Quote Link to comment Share on other sites More sharing options...
will4x4 Posted July 22, 2010 Author Share Posted July 22, 2010 even though the volt meter is shownig its charging fine? seems really odd Quote Link to comment Share on other sites More sharing options...
western Posted July 22, 2010 Share Posted July 22, 2010 alt will still charge if the belt is slightly slack, but could just enough to put the light on Quote Link to comment Share on other sites More sharing options...
brighouse shed Posted July 22, 2010 Share Posted July 22, 2010 took my battery off this weekend for a spot of hot metal glue gun play. same problem no issue starting just the light comes on applied some more effort to tightening the battery connections, ..........cured Quote Link to comment Share on other sites More sharing options...
errol209 Posted July 23, 2010 Share Posted July 23, 2010 even though the volt meter is shownig its charging fine? seems really odd 13.5V isn't "charging fine", it's just "charging". An alternator in 100% nick running at a few 1000 rpm should be giving you 14 - 14.5V. Have you measured the voltage accross the big terminals on the back of the alternator, to eliminate a bad earth problem? What reading is the warning light terminal giving you? if its more than 14.5V then as Ralph suggested it could be a regulator pack fault. Quote Link to comment Share on other sites More sharing options...
will4x4 Posted July 26, 2010 Author Share Posted July 26, 2010 Hi bit of an update. It is the alternator that needs changing.. i bought a second hand one from a 300tdi discovery however the pulley is different. I have tried to change it over but cant for the life of me get this one off, any ideas or tips? Also thought i might just get a new one and it seems the 65amp replacement part is £110 and the 100amp upgrade is £100 however i would will still need to change the pulley or buy a different belt? I'm a bit confused now can someone shed some light i just want to get her charging again with a simple bolt in bolt out job without having to change the belts as (i bought a few spare this size) and if i can upgrade it if it wont cost much to do so ... thank in advance Confused Will Quote Link to comment Share on other sites More sharing options...
errol209 Posted July 26, 2010 Share Posted July 26, 2010 It's a while since I did it, but it went as follows: 1) undo the pulley securing nut so that it is still on but right at the end of the thread 2) clamp pulley in Workmate so that alternator hangs down underneath 3) apply small amounts of 3-in-1, WD40 or Plusgas to threads 4) make and deploy beverage of choice 5) put a bit of scrap timber over the nut and tap authoritatively with LR special tool No. 1 (hammer) until the alternator drops onto the nut. Don't hit it very hard, as you can break the lip off the pulley and / or knacker the bearings, but it will go eventually. Quote Link to comment Share on other sites More sharing options...
will4x4 Posted July 26, 2010 Author Share Posted July 26, 2010 Thanks errol but thats the prob i cant get passed stage 1 :)the 24mm nut Quote Link to comment Share on other sites More sharing options...
western Posted July 26, 2010 Share Posted July 26, 2010 if you've gone for the 100amp Alternator upgrade the main brown cables to the battery & starter motor otherwise you'll have more problems later. another run of cable, the same size as the existing wires & attached to the same place both ends will be fine. Quote Link to comment Share on other sites More sharing options...
errol209 Posted July 26, 2010 Share Posted July 26, 2010 Thanks errol but thats the prob i cant get passed stage 1 :)the 24mm nut Go 2), 3) then 1) Quote Link to comment Share on other sites More sharing options...
western Posted July 26, 2010 Share Posted July 26, 2010 IIRC isn't there a allen key socket in the end of the alternators shaft, if so, use a suitable size allen key to hold the shaft while undoing the nut. Quote Link to comment Share on other sites More sharing options...
will4x4 Posted July 26, 2010 Author Share Posted July 26, 2010 prob is you cant hold an Allen key on it with a nut on it. think ill drop it in and use an air gun on it. With the upgrade on the wiring that goes from alternator to start motor to battery can i just add another wire from alternator straight to battery? Cheers Quote Link to comment Share on other sites More sharing options...
western Posted July 26, 2010 Share Posted July 26, 2010 prob is you cant hold an Allen key on it with a nut on it. think ill drop it in and use an air gun on it. With the upgrade on the wiring that goes from alternator to start motor to battery can i just add another wire from alternator straight to battery? Cheers as I posted above -- another run of cable, the same size as the existing wires & attached to the same place both ends will be fine but you need to find out what size cable is already fitted, so you can have either a new much thicker cable or 2 lengths of the same original size cable to battery & starter. Quote Link to comment Share on other sites More sharing options...
will4x4 Posted July 26, 2010 Author Share Posted July 26, 2010 Thanks for all your help its fixed. Managed to get the pulley off and its all good .....for now. another job learnt. (i can take an alternator out in 10 mins now) Quote Link to comment Share on other sites More sharing options...
western Posted July 26, 2010 Share Posted July 26, 2010 Excellent, we never stop learning Quote Link to comment Share on other sites More sharing options...
will4x4 Posted July 26, 2010 Author Share Posted July 26, 2010 Yep, i really knew it would be a bad idea to set fire to the truck this morning Quote Link to comment Share on other sites More sharing options...
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