Chilp3 Posted November 5, 2015 Report Share Posted November 5, 2015 Good afternoon forum members, I was asked by a fellow member to assist him with a failed rev-counter on his 1973 CR TR6. The instrument has simply stopped working with no obvious signs of failure. All other instruments are working fine including the two bulbs in the rev-counter which illuminate when you turn the ignition on. I have checked the fuses and the fuse box which all seems fine. I have also checked the drive from the distributor (at the distributor end) which also appears to be working OK. I have suggested that we will need to remove the instrument to have a look at the drive in the back as I guess this may also be the cause of the problem? I was wondering if anyone has had any similar experiences and what was the route cause(s) of the problem. Once we have removed the instrument are there any checks (mechanical and electrical) that we can perform to determine the problem? I would be grateful if any electrical checks could be translated into layman's terms as electrics are not my strong point! thank you. I do however have a decent multi-meter which I can use subject to instructions. Thanks for taking the time to read this post and offer any suggestions. Best Regards, Peter Quote Link to post Share on other sites
ed_h Posted November 5, 2015 Report Share Posted November 5, 2015 Other than the illumination, the stock rev counter is not electronic--it is mechanical. So if the lights are working, a multimeter isn't going to be of much use in diagnosis. You'll probably have to open the case. Or send it out. Ed Quote Link to post Share on other sites
peejay4A Posted November 5, 2015 Report Share Posted November 5, 2015 You could try undoing the drive cable at the instrument end then run the engine to see if the square end of the inner cable rotates. If it doesn't the fault lies with the cable or the distributor drive gear. If it does rotate the instrument is at fault. Quote Link to post Share on other sites
Kevo_6 Posted November 5, 2015 Report Share Posted November 5, 2015 Good afternoon forum members, I was asked by a fellow member to assist him with a failed rev-counter on his 1973 CR TR6. The instrument has simply stopped working with no obvious signs of failure. All other instruments are working fine including the two bulbs in the rev-counter which illuminate when you turn the ignition on. I have checked the fuses and the fuse box which all seems fine. I have also checked the drive from the distributor (at the distributor end) which also appears to be working OK. I have suggested that we will need to remove the instrument to have a look at the drive in the back as I guess this may also be the cause of the problem? I was wondering if anyone has had any similar experiences and what was the route cause(s) of the problem. Once we have removed the instrument are there any checks (mechanical and electrical) that we can perform to determine the problem? I would be grateful if any electrical checks could be translated into layman's terms as electrics are not my strong point! thank you. I do however have a decent multi-meter which I can use subject to instructions. Thanks for taking the time to read this post and offer any suggestions. Best Regards, Peter Hi Peter As Ed has written, it's mechanical. On occasions my rev counter appears not to work but I give it a few taps on the glass and hey presto. Could be something inside sticking, in need of lubrication. Cant offer any other help as I've never taken one apart. Quote Link to post Share on other sites
snowric Posted November 5, 2015 Report Share Posted November 5, 2015 Mine did this and it turned out that the inner cable had fractured. Quote Link to post Share on other sites
seanshine Posted November 5, 2015 Report Share Posted November 5, 2015 I'd take a look at the drive gear inside the distributor. Took mine apart when my tach failed. The platic teeth on the drive gear were knackered. Easy fix. I was so glad that it was not the tach itself. Took maybe a half hour to replace the gear. SS Quote Link to post Share on other sites
Nigel Triumph Posted November 5, 2015 Report Share Posted November 5, 2015 The fit & forget solution is to get the tacho converted to electronic. Speedy Cables did this for my CP-sseries TR6. They fit a modern electronic package inside the original instrument. Looks totally original and works perfectly with none of the usual needle flicker. Nigel Quote Link to post Share on other sites
TR NIALL Posted November 5, 2015 Report Share Posted November 5, 2015 (edited) Removed. Edited November 5, 2015 by TR NIALL Quote Link to post Share on other sites
oldtuckunder Posted November 5, 2015 Report Share Posted November 5, 2015 Only really to summarise previous suggestions into a check list 1) Its Mechanical 2) Disconnect cable at distributor 3) In distributor you will see a tube with a square inner (if its gone round that could be the problem) Nb it may have gone round for an upstream problem. Put a matchstick or something similar in the square hole, start the engine, if the match stick goes around the distributor drive is probably OK, not conclusive but worth doing the next checks before striping distributor. 4) Can you turn the inner cable end? if not something seized towards rev counter 5) Can you pull the inner out? If so has it broken just up stream of the distributor (a common fail point) 5a) has the end of the inner cable rounded off rather than being square? Ok everything apparently OK at distributor end, so reconnect everything and move to rev counter end 6) unscrew cable from back of speedo, awkward but doable 7) Will the inner cable pull out, i.e. has it sheared close to the end (another common fail point) 8) Start the engine, is the inner going round? if not broken inner 9) Has the end of the inner rounded off rather than being square? Found the problem yet? No... 10) Take the rev Counter out 11) Has the square in the rev counter drive rounded off? 12) Put something into the square drive on the rev counter and spin with fingers, even this should cause the needle to flick or is it seized. Found the problem yet? No... Well there is a problem at either the distributor or rev counter end (probably) :-) If it proves to be the rev counter then seriously think about having it converted to electronic, you wont regret it and its a bunch less mechanical things to fail in the future. Alan Quote Link to post Share on other sites
stuart Posted November 5, 2015 Report Share Posted November 5, 2015 You could also have a problem at the Gearbox End,the Angle Drives that attach the Cable to the GB are a known to fail. Rev counter Niall Stuart. Quote Link to post Share on other sites
TR NIALL Posted November 5, 2015 Report Share Posted November 5, 2015 Rev counter Niall Stuart. Grey Cells. Quote Link to post Share on other sites
Chilp3 Posted November 6, 2015 Author Report Share Posted November 6, 2015 Just wanted to say thank you to everyone for posting all of these really helpful suggestions. I will update the forum when we have more news. Best Regards, Peter Quote Link to post Share on other sites
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