Boydie Posted February 21, 2015 Share Posted February 21, 2015 Driving in fog the other morning my Disco just died, then restarted - quite odd. I lost all my radio channel settings so I can only assume that for some reason beyond my understanding there was an obvious momentary break in electrical supply. The main 100 amp CB was fine as were all the other mini CB (I replaced all the fuses with mini circuit breakers) it hasn't happened again so I'm mystified as to the reason, could the alternator, which is only 2 years old be faulty ???? Any ideas ??? Quote Link to comment Share on other sites More sharing options...
Maverik Posted February 21, 2015 Share Posted February 21, 2015 Contacts on a master isolator switch/emergency cut off switch possible on way out? Admittedly a tad strange while driving, but I had a switch go once, its symptoms where a loud click and electricery disapearing when you tried to start it... But as an engine once started with a healthy alternator would probably keep itself going if you pulled the battery supply, so if it was an electric problem it must have interfered with the battery/alternator supply at the same time... Quote Link to comment Share on other sites More sharing options...
Ash.Witty Posted February 21, 2015 Share Posted February 21, 2015 Check the battery terminals are tight and where they connect to at the other end. Quote Link to comment Share on other sites More sharing options...
ejparrott Posted February 22, 2015 Share Posted February 22, 2015 IIRC the wiring on a standard 300 is such that it doesn't need the battery to run once it's started, feed being directly from alternator to start stud to dash, certainly my 200 is/was. If yours is the same you can discscount the battery, unless you happened to loose the battery and the alternator at exactly the same second. Wasn't a loose connection on the stop solenoid was it? bump in the road? Edit : can't be the solenoid if you lost radio channels too Quote Link to comment Share on other sites More sharing options...
Daan Posted February 22, 2015 Share Posted February 22, 2015 bad earth? Daan Quote Link to comment Share on other sites More sharing options...
Josh NZ Posted February 22, 2015 Share Posted February 22, 2015 Intriguing problem this.. Could it be a dead short? Sudden interruption to the constant live power supply which controls such things as radio settings but only momentarily. Odd with the CB still working though. Does the stop solenoid operate through earthing or is it a positive-ly operated switch? (If you get what I mean.. It always makes sense in my head) Could a small section of the wire have chafed through? Quote Link to comment Share on other sites More sharing options...
western Posted February 22, 2015 Share Posted February 22, 2015 stop solenoid needs 12 volts to open it to allow fuel to pass. the feed wire does get hard /brittle, it could short out on another metal part.but it wouldn't or shouldn't interupt the radio. Quote Link to comment Share on other sites More sharing options...
Simon Smith Posted February 22, 2015 Share Posted February 22, 2015 Radio gets it's feed from aux terminal on ign switch, stop solenoid gets it's feed from the ign terminal on the ignition switch. If everything else worked my money is on the ignition switch or the main feed to it from the fusebox. First thing I would check is the wiring round the steering column and the multi plug. Quote Link to comment Share on other sites More sharing options...
PaulN Posted February 22, 2015 Share Posted February 22, 2015 After following above - Spider? Quote Link to comment Share on other sites More sharing options...
Nigelw Posted February 22, 2015 Share Posted February 22, 2015 Knowing you modified your harness, have you secured all the terminals in the terminal blocks securely? God knows I needed to fettle a couple of multi plugs after the initial rewire in my 200. Quote Link to comment Share on other sites More sharing options...
Boydie Posted February 23, 2015 Author Share Posted February 23, 2015 my alternator supply passes through a 100 amp CB (manual re-set) to the main battery, from there it powers the aux. battery via a RedArc and a second 100 amp CB. Power to the general supply passes through a 70 amp CB to the ignition. None of these CB popped, Quote Link to comment Share on other sites More sharing options...
Rangy35 Posted February 23, 2015 Share Posted February 23, 2015 A bad earth will not make any of you citcuit breakers pop. I will start with all main earths and work my way to the small ones. Battery terminal first and then the chassis and gearbox earth would be my starting point. Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted February 23, 2015 Share Posted February 23, 2015 Alternator return is bolted to the block which should keep the reference to 0V in place , so if its a duff earth it must be loom to chassis rather than battery to chassis. The radio will also get an inadvertent ground through its antenna connection so to me it does point to body > chassis connection missing for a few seconds. there is a flaw in that though as the stop solenoid is grounded to the block. any warning lights or did it all just go black? When I read the first post I also suspected a momentary +ve to -ve short but the contact breakers staying in seems to rule that out. Quote Link to comment Share on other sites More sharing options...
elbekko Posted February 23, 2015 Share Posted February 23, 2015 If the earth connection between the battery and chassis is broken, it could happen. IIRC the engine takes its earth from the chassis, not directly from the battery. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 23, 2015 Share Posted February 23, 2015 That's all well and good, but the alternator, attached to the engine by a bolt for an earth, would keep the engine running in the event of taking the battery off, surely? Does the main battery feed and alternator charge wire go to starter motor on a Disco like a defender or to a firewall bobbin like an RRC? Either way I would be looking here for sure, as that is where all the system power comes from, be it ignition feed or permanent, as for the radio. The only other possibility in my mind is 2 separate faults. Quote Link to comment Share on other sites More sharing options...
ejparrott Posted February 23, 2015 Share Posted February 23, 2015 Yes it will. I've jump started my 200 using another battery and it will keep running with no battery on it. Quote Link to comment Share on other sites More sharing options...
Boydie Posted February 24, 2015 Author Share Posted February 24, 2015 All the above ring true don't appear to be the answer, if it ever does it I again I will do more complete on road inspection, as I said, the odd thing was, I was driving along, then for no more than a couple of seconds, no power - no electrics, no lights, nothing --- then everything back !! the only thing that indicated a 100% electrical failure was the radio loosing its channel memory. If it was the alternator the battery would still power the car, if it was the main battery that suddenly died then the alternator would do the same, I can only think of a mysterious break in the supply from the 70 amp CB to the ignition switch, so I will look at that but so far the megga test of that circuit is positive. Quote Link to comment Share on other sites More sharing options...
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