SPendrey Posted August 28, 2018 Share Posted August 28, 2018 This is a 1994/5 Disco 300Tdi... drove well between Swindon and Bristol airport last Friday, didn't move Saturday, Sunday morning it was very sluggish to start. Voltage (from 3rd party display in car) read 8.something volts while cranking, but it did start! Ignored it until last night (Monday), voltage across battery is reading 4.something volts. Popped in 'spare' (old) battery this morning, started up, and in-car display is showing 18V! Stopped, checked battery and it showed 12.2V. Thinking the alternator is faulty and overcharging, which would cause the first battery to fail? Didn't notice voltage display at time to see fault. However, when I was poking around today I felt the middle terminal (D+) on alternator was hot. Car hasn't run for more than 2 minutes, and that was 6 hours ago! Time for a new alternator? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted August 28, 2018 Share Posted August 28, 2018 Certainly time for a new regulator, depending on the alternator type you may well be able to change it yourself, for a few pounds versus lots more pounds. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 28, 2018 Share Posted August 28, 2018 Might be worth checking the terminations, I can't remember exactly but IIRC the alternator needs the reference voltage from the charge lamp to regulate itself, otherwise it'll try to hit ~110v Quote Link to comment Share on other sites More sharing options...
SPendrey Posted August 28, 2018 Author Share Posted August 28, 2018 31 minutes ago, FridgeFreezer said: Might be worth checking the terminations, I can't remember exactly but IIRC the alternator needs the reference voltage from the charge lamp to regulate itself, otherwise it'll try to hit ~110v You mean the terminations at the alternator? All seemed fine except for the middle one having some rubbery stuff on it - perhaps related to the regulator inside the cover being black and burnt looking? Quote Link to comment Share on other sites More sharing options...
Peaklander Posted August 28, 2018 Share Posted August 28, 2018 On my A127 alternator the regulator packed-up recently during a day-long journey. The displayed voltage suddenly went all over the place during engine running. It would sit at 14v or thereabouts then suddenly jump to 16, 17 or even 18 volts before settling down again. This went on for a couple of hours before we realised that something had to be done. I think you would notice this if you can view the voltage when running. It is certainly worth replacing the regulator if your alternator is anything like as easy as the A127. Somewhere on here there's a top tip about how to fit it that involves using a paper clip in the holes to hold back the brushes until they are over the rotor. The regulator cost me €8. Quote Link to comment Share on other sites More sharing options...
SPendrey Posted August 29, 2018 Author Share Posted August 29, 2018 Will look for a replacement regulator, at least so I can keep the alternator as a "spare", since I seem to keep lots of spares! (Don't we all?) I believe I'm looking for the piece outlined in blue? Quote Link to comment Share on other sites More sharing options...
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