andygood Posted August 19, 2013 Share Posted August 19, 2013 Hi folks, So I was driving home last Thursday night and I got the multiple warning lights issue that a number of people seem to be having lately. (battery, cat, rear lights & oil level). I checked the voltage across the battery and sure enough, there was no increase in voltage with the engine running and revving slightly. Was booked in for new timing belt & brakes on Friday, so asked the guy to check the alternator. He pulled it and sent it next door to an alternator specialist, who said it was goosed and supplied a new Denso unit. Got the car back with everything looking good! While out for a drive yesterday, I noticed a slight whine from the engine bay. A short while later all the warning lights came on again... Pulled in, switched off and checked under the hood. Burning smell in engine bay, coils in alternator had gone from brown to black. Went to restart and found that the car was dead. No ignition lights, nothing. Hooked up the GF's car to jump start and some grease on the cable clips started smoking. Unhooked the +VE lead from the alternator and turns out the alternator was shorting the battery. Was then able to jump start the car but not enough battery left to keep it going. Probably not relevant, but a few weeks ago I replaced the thermostat, plugs, HT leads, dizzy cap and rotor. Also, mechanic said that the old belt tensioner was in a bad state and the old timing belt was a bit slack... So, any ideas what might be causing the car to eat alternators? Will do tippex test and check aux belt this afternoon. Cheers, Andy. Quote Link to comment Share on other sites More sharing options...
James Posted August 19, 2013 Share Posted August 19, 2013 I was going to suggest checking the crank pulley, but it looks like that is your intention anyway. Quote Link to comment Share on other sites More sharing options...
mellonman Posted August 19, 2013 Share Posted August 19, 2013 i would say faulty unit, take it back, if your crank pulley had failed your alternator wouldnt spin thuse would not be able to burn out and short the battery, no harm in checking though as the alernator could now be stuck solid and damage belts and pulley Quote Link to comment Share on other sites More sharing options...
mattdavies Posted August 19, 2013 Share Posted August 19, 2013 Do you have aftermarket pulleys ? If you have smaller alternator and bigger crank you will be spinning the alternator too much now. Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted August 19, 2013 Share Posted August 19, 2013 (edited) You would have to have a really bad short-circuit to destroy an Alternator - and that short-circuit would have to be on a REALLY thick lead (like the main feed to your Starter Motor) Have you worked on the car lately? Is there any way you have disturbed something such that it could be shorting out? Alternators consist of TWO parts - the generator, which is the coils etc, and the electronics, which contains Rectifiers to convert the AC from the generator to DC plus Transistors to regulate the maximum output to around 13.8 Volts. If those Transistors fail they normally go Open Circuit, so nothing is shorted out. However, it is possible that your new one went short circuit, which would cause the symptoms you describe. So definitely take it back ! I presume it wasn't actually a NEW one (which would cost a fortune) - more likely you were sold a Reconditioned One for £40 - £80? (where they usually just replace the Power Transistors or Rectifiers inside, whatever had failed) Personally, these particular Alternators are SO reliable that if one DID fail I would just fit a Secondhand one (which ought to cost you about £20 from a scrapper) Edited August 19, 2013 by Roger NE (see edit history) Quote Link to comment Share on other sites More sharing options...
straightsix Posted August 19, 2013 Share Posted August 19, 2013 Looked in the Cargo catalogue - although looking the same, some of the wiring plug's wires go into different terminals. Possibly worth checking? The wiring MUST be checked before fitting a new unit in case it shafts that one too. Quote Link to comment Share on other sites More sharing options...
andygood Posted August 20, 2013 Author Share Posted August 20, 2013 Hi guys, Thanks for the responses! I was going to suggest checking the crank pulley, but it looks like that is your intention anyway. Tippex-test checks out ok, assuming I did it right... (two lines across the gap in the outer, large-diameter part of the pulley, drove 20km home, lines still matched up). i would say faulty unit, take it back, if your crank pulley had failed your alternator wouldnt spin thuse would not be able to burn out and short the battery, no harm in checking though as the alernator could now be stuck solid and damage belts and pulley Going back this morning to have it checked! Do you have aftermarket pulleys ? If you have smaller alternator and bigger crank you will be spinning the alternator too much now. No, the pulleys are all stock originals. While the alternator is a brand new Denso unit, StraightSix's comment below sounds promising... You would have to have a really bad short-circuit to destroy an Alternator - and that short-circuit would have to be on a REALLY thick lead (like the main feed to your Starter Motor) Have you worked on the car lately? Is there any way you have disturbed something such that it could be shorting out? Alternators consist of TWO parts - the generator, which is the coils etc, and the electronics, which contains Rectifiers to convert the AC from the generator to DC plus Transistors to regulate the maximum output to around 13.8 Volts. If those Transistors fail they normally go Open Circuit, so nothing is shorted out. However, it is possible that your new one went short circuit, which would cause the symptoms you describe. So definitely take it back ! I presume it wasn't actually a NEW one (which would cost a fortune) - more likely you were sold a Reconditioned One for £40 - £80? (where they usually just replace the Power Transistors or Rectifiers inside, whatever had failed) Personally, these particular Alternators are SO reliable that if one DID fail I would just fit a Secondhand one (which ought to cost you about £20 from a scrapper) The alternator is a brand spanking new €200 worth of Denso OE... There was defo a short circuit from the thick positive cable which is bolted to the side of the alternator. As I pulled it off there was much sparking and then the power came back on the dash, alarm etc. Bloody battery was red hot and took about five hours to cool down... Looked in the Cargo catalogue - although looking the same, some of the wiring plug's wires go into different terminals. Possibly worth checking? The wiring MUST be checked before fitting a new unit in case it shafts that one too. Thanks for this info! I will check it out and see if it pans out... Thanks again, all! Quote Link to comment Share on other sites More sharing options...
andygood Posted August 20, 2013 Author Share Posted August 20, 2013 Looked in the Cargo catalogue - although looking the same, some of the wiring plug's wires go into different terminals. Possibly worth checking? The wiring MUST be checked before fitting a new unit in case it shafts that one too. ok, I just checked and the new alternator is a Denso, part number 27060-46120. Searching the forum this is a standard 100 Amp part. Next question, is a 100 Amp alternator ok to put on a manual NA? Should I be using a 90 or even an 80 Amp one instead? Cheers, Andy. Quote Link to comment Share on other sites More sharing options...
straightsix Posted August 20, 2013 Share Posted August 20, 2013 Pretty sure (if my memory serves me correctly) that NAs had 100amp alternators and a TT had 110amp Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted August 20, 2013 Share Posted August 20, 2013 (edited) Andy the rating in Amps on an Alternator is the MAXIMUM output current it will supply So just like power ratings on Loudspeakers, the bigger the number, the less likely it is to blow up ! That means it doesn't really matter what rating Alternator you fit, it's just less likely to fail the higher the Max output. In terms of what takes a lot of current from the Alternator in a car when the engine is running, it's mainly Headlamps, Heated Rear Window, Electric Fans (if you have them) and Music Systems . . . . Even with all of those switched on, in reality you're unlikely to ever draw more than 50 Amps. Then there's intermittent things, like horns, electric windows, wipers . . . but each of those only take up to about 10 Amps each. Unfortunately you may find that the Alternator going short circuit may have permanently damaged your battery (surprised there's no main fuse in the Mk4 Supra - there is in the Mk3) Edited August 20, 2013 by Roger NE (see edit history) Quote Link to comment Share on other sites More sharing options...
andygood Posted August 22, 2013 Author Share Posted August 22, 2013 So it turns out that the new alternator was faulty and was shorting the battery through the 'B' terminal. Thankfully the battery didn't go postal and take the car with it, just after I put €2k of new parts into it... Must've been enough resistance through the dud alternator to save it... Charged it overnight and it seems to be okay so far. It also turned out that the alternator guy had got the required parts in the mean time and reconditioned my old alternator, so we put that one back in the car and everything's cushty! Thanks again for the tips... Quote Link to comment Share on other sites More sharing options...
James Posted August 22, 2013 Share Posted August 22, 2013 So it turns out that the new alternator was faulty and was shorting the battery through the 'B' terminal. Thankfully the battery didn't go postal and take the car with it, just after I put €2k of new parts into it... Must've been enough resistance through the dud alternator to save it... Charged it overnight and it seems to be okay so far. It also turned out that the alternator guy had got the required parts in the mean time and reconditioned my old alternator, so we put that one back in the car and everything's cushty! Thanks again for the tips... Good news! I'm glad it is alright! At least you also have the reassurance through the tippex test that the crank pulley is fine and well as well. Quote Link to comment Share on other sites More sharing options...
andygood Posted August 22, 2013 Author Share Posted August 22, 2013 At least you also have the reassurance through the tippex test that the crank pulley is fine and well as well. Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted August 23, 2013 Share Posted August 23, 2013 Glad you got it sorted ! Presume you got all your money back for the faulty new Alternator? (and hopefully the Reconditioning of your old Alternator was a lot less than the new one?) Quote Link to comment Share on other sites More sharing options...
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