Nutter Posted July 1, 2004 Posted July 1, 2004 Can anyone help? Running a 1700 X Flow with lucas distributer and aldon automotive flame flower coil. Rev counter readings are higher than what the engine is actually doing! flickering around alot. Clubman revlimiter also installed. VDO instruments. Anyone with the same problem or got any solutions? Quote
StuartMackay Posted July 1, 2004 Posted July 1, 2004 same problem here.....checked all earths and wiring...reads nothing until ignition light goes out then still fluctuates, reads at least 1000 revs too high always and goes mental when you switch lights on, had two VDO ones which do the same.....tried a cheap elctronic tacho and guess what..its perfect!! VDO one is on its way back to VDO in Brum tomorrow. Quote
itguy Posted July 2, 2004 Posted July 2, 2004 Nutter - have you checked independantly what engine revs it is actually doing? I.E. multifunction strobeascope or anything, reading off the plug lead? Reason I ask is I have been having problems with my microdynamics dizzy and my VDO was reading double below about 2000rpm, after that it was accurate. When we checked my cars revs off the plug lead, it too was reading high - nothing wrong with the VDO. I am now on the hunt for a new dizzy to try..... My saga continues.. Will. Quote
alfie_fraser Posted July 2, 2004 Posted July 2, 2004 As addition I too have problems but with the speedo, which reads eretically at low speeds i.e. blips to 80mph when doing 0-5mph?? Not got a clue Cheers Gareth Quote
Matt Seabrook Posted July 2, 2004 Posted July 2, 2004 I have chucked my VDO rev counter, as it was crap. It got the 5000 rpm and than dropped to 2-3000 even though the engine was revving harder. Fitted a different rev counter and now all is well. Quote
Nutter Posted July 2, 2004 Author Posted July 2, 2004 Checked everything that I possibly could! Engine tickover at 750 rpm, reading at 1200. When you take your foot off the gas rev counter will say go from 6500 down to 4000. Might try a different rev counter. Quote
Nutter Posted July 2, 2004 Author Posted July 2, 2004 Stuart, Where did you get your cheap tacho from? Nutter Quote
StuartMackay Posted July 2, 2004 Posted July 2, 2004 My local friendly garage had a cheap Carlos Fandango pod mount 1970's one lying around (Probly from a scrapped Mk1 Escort 1100L of unknown vintage!! which we used as a comparison test. I suspect there is a bad batch of tachos floating around as this is the replacement from westfield that still exhibited the same problems as the original. The original one worked fine for a 1000 miles or so then developed its random rev generating characteristics, which coincided with a new engine installation, so you can imagine the B****ring about I have been through trying to trace the fault. The Guy at VDO to contact is: Joe Cooke Siemens VDO 38 Gravelly Industrial Park Birmingham B24 8TA Tel: 0121 326 1170 email: joe.cooke@siemens.com I spoke to him back in February and he hadnt come across this problem, he was very helpful, I hope he remains so when he receives my tacho back on his desk on Monday. Quote
StuartMackay Posted July 5, 2004 Posted July 5, 2004 Joe from VDO called today within a coupe of hours of receiving my old tacho (what service!!!! saying he could find no faults on my tacho...but is sending me a brand new one foc just in case.......what a nice guy Quote
Nutter Posted July 6, 2004 Author Posted July 6, 2004 Let me know if you put the new VDO tacho in. Will be interesting to see the results? Quote
StuartMackay Posted July 8, 2004 Posted July 8, 2004 YEEHAH!! Problem solved!! The ever helpful Joe from VDO included a diode in the package with the checked tacho. I was sceptical.....However, It is sorted ....... No high readings now, (idles at 900 rpm), no wild (high)fluctuations when you switch the lights or wipers on, sits there as steady as a rock right through the rev range to valve bounce.......To think I have been messing about with this for nearly 9 months now, and such a simple solution Fit a IN4001 diode (probly all of 2p worth)between the coil feed to tacho, I did this by crimping the diode between a male and female lucar connector in series and potting the diode in epoxy resin, plug the diode onto the coil tacho feed terminal and then plug the two white/black trace feed wires which go to terminal 3 on the tacho and in and enjoy fluctuation free rev information!! Chuffed tabitz Quote
Nutter Posted July 9, 2004 Author Posted July 9, 2004 Stuart, Great News!!! At last a solution. So all that your saying is put this diode inline to the tacho. Easy when you know how!!! Take it easy. Quote
Enterpryse Posted July 10, 2004 Posted July 10, 2004 Which way round did you connect the diode? Quote
Nutter Posted July 10, 2004 Author Posted July 10, 2004 Weeeeeeeeeeeeeeeeeeeeeheyyyyyyyyyyyyyyyyy Sorted, Wiring slightly different though. Got hold of a diode, the black/white wire from the coil to connection 4 of the tacho is the one (on my motor anyway), split this and put the diode inline, with the solid grey band facing towards the tacho connector block. Probably best to set in expoxy or similar as the diode is quite fragile. Quote
Enterpryse Posted July 11, 2004 Posted July 11, 2004 I've got a few of these made up as little mod kits if anyone needs one. These fit on the coil in line with the tacho feed. Quote
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