amski Posted February 3, 2008 Share Posted February 3, 2008 first thing.... hello to all disco owners! im new to all this so please be nice! right i was out this morning driving about and me rev counter kept dropping and then going back! has anyone else had this happen and mostly how do i stop it! cheers adam Quote Link to comment Share on other sites More sharing options...
The Welder10 Posted February 3, 2008 Share Posted February 3, 2008 first thing.... hello to all disco owners! im new to all this so please be nice! right i was out this morning driving about and me rev counter kept dropping and then going back! has anyone else had this happen and mostly how do i stop it! cheers adam Hi amski, check the wires at the back of your alternator, they may be loose or corroded, hope this helps. Quote Link to comment Share on other sites More sharing options...
RRX Posted February 3, 2008 Share Posted February 3, 2008 Petrol or Diesel?? Quote Link to comment Share on other sites More sharing options...
istruggle2gate11 Posted February 3, 2008 Share Posted February 3, 2008 loose wire, alternator belt slipping, alternator going us, dicky gauge for a few! Quote Link to comment Share on other sites More sharing options...
teabag Posted February 3, 2008 Share Posted February 3, 2008 The rev counter picks up pulses from the alternator therefore check all the electrical connections at the alternator..It's a common problem. Quote Link to comment Share on other sites More sharing options...
Philj Posted February 3, 2008 Share Posted February 3, 2008 Is it going mad or just not working, or only working when above a certain rev limit ? Mine stopped registering below 2000rpm - it was a precursor to my alternator belt snapping. Quote Link to comment Share on other sites More sharing options...
Discovan300tdi Posted February 3, 2008 Share Posted February 3, 2008 mine was doing the same thing on a 300tdi the wire from the alternator had come loose and wasnt making avery good contact Quote Link to comment Share on other sites More sharing options...
peter deer Posted February 3, 2008 Share Posted February 3, 2008 Mine did that before alterantor failed (bearing) Peter Quote Link to comment Share on other sites More sharing options...
jas97disco Posted February 3, 2008 Share Posted February 3, 2008 I had this with my speedo - looks like the needle just worked loose on the spindle so you may have the same thing. Only does it a few times a year. It can read, for example, 70mph then suddenly drop to zero then either sits at zero for a while (say 15mins) and sorts its self out again or bounces between 0 and 70 for a while and sorts itself out. Quote Link to comment Share on other sites More sharing options...
amski Posted February 3, 2008 Author Share Posted February 3, 2008 ah yeah! 300 tdi, thanks for the responce chaps, will have a look tomorrow and will let you know how i get on cheers adam Quote Link to comment Share on other sites More sharing options...
Roverdrive Posted February 5, 2008 Share Posted February 5, 2008 IIRC the wire for the tacho is grey and white and is fed from the back of the alternator Quote Link to comment Share on other sites More sharing options...
Matt B Posted February 18, 2008 Share Posted February 18, 2008 I've just aquired a 300TDi which has no movement from the Rev counter at all, I did a con test on the grey/white wire and it is fine, the terminals on the alt are clean and it has a new spade connector - what's next to check? Matt Quote Link to comment Share on other sites More sharing options...
katluke Posted February 18, 2008 Share Posted February 18, 2008 I've just aquired a 300TDi which has no movement from the Rev counter at all, I did a con test on the grey/white wire and it is fine, the terminals on the alt are clean and it has a new spade connector - what's next to check?Matt Good question.My rev counter is also dead. Quote Link to comment Share on other sites More sharing options...
stageonesimmo Posted February 18, 2008 Share Posted February 18, 2008 Put a voltmeter on AC between the 'W' terminal and earth and check that with the engine running you have a voltage, (its AC as its un-rectified from one of the windings, the trickery on the back of the tacho converts the signal to movement at the needle), that rises and falls with engine speed. If you don't - the alt may well still be charging but its on its way out, if you do - suspect a failure of the tacho or wiring/printed circuit at the instrument cluster. I recently had to cut the white/gray wire back on mine and used crimp connectors to splice in a new length as my gas soldering iron has expired and guess what - the symptoms are back so I'm going to have to open the loom up even further and try again. Yawn, landies, don't ya just love 'em............... Quote Link to comment Share on other sites More sharing options...
Matt B Posted February 19, 2008 Share Posted February 19, 2008 Thanks for the info, I'll give that a go later. Matt Quote Link to comment Share on other sites More sharing options...
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