My P6 V8s tachometer has two connections on the back. I'm not sure that is reading correctly. Before I removed it from the circuit board it would sometimes drop down or not work at all on other occasions it seemed fine. If I tapped the Perspex screen it would work normally. I removed and refitted the connections The connection which accepts the bullet connector on the back of the tachometer moves around. I refitted the connections then reassembled the instruments. It now works consistently but the reading are lower. How many revs should it read in fourth at 30, 50 and 70 mph? Any assistance gratefully received.

Glen :)


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Staff member
Hi Glen,

The tacho in the Rover that belongs to a friend of mine behaves like yours was doing, sometimes working, other times not, and tapping the Perspex screen would snap it into life. It has been doing this for maybe 20 years.

In 4th which has a ratio of 1:1, at 30mph...1250rpm, at 50mph...2083rpm, and at 70mph,...2917rpm. So for the latter two in round figures, just over 2000rpm and just on 3000rpm.



Active Member
On another thread I'm working through a problem with mine, which I've realised is probably best described as a twitch rather than a wobble. Done the oil, checked the connectors at the back, checked the connection at the coil end... still twitching.
Hi everybody.
I have a very similar problem with my revcounter in Rover. Now and again it stops reading and then starts again, recently stopping all together. So out it came and of it went to an instrument technition, who said after an examination that there was nothing wrong with it, but if Rover had electronic igination the instrument was not suitable. I did not belive him as it had worked reliably when I first had Rover. I refited it and it is up to its old intermitint reading. So my question is, is it suitable for electronic ignition which Rover has?

Your instrument technician is almost certainly correct . The RVI type instrument which was designed to count the impulses in the ignition low tension circuit as the points opened will not reliably work with most electronic systems . There are circuit boards available to convert to later type voltage sensing instruments, which usually will work with electronic systems, but unless you DIY , it is not a cheap solution . If you look closely at your tacho face , you will probably see RVI and a number printed on it
Hi. Thankyou for the reply. I have looked at the rev counter from the 1974 parts Rover I had and the rev counter on that has the designation RVC 2412/100. I wonder if it is suitable for electronic ignition and if so I might be able to transfer it?
John : yes, the RVC type is a voltage sensing instrument and should work . You will need to alter the wiring however to create a sensing loop and to provide 12volts to the instrument
christopher storey said:
Whiterover asked me if I could suggest a sorce for circuitboards to convert from RVI to RVC . This seems as though it would be a starting point

http://www.ebay.ca/itm/Smiths-RVI-RVC-T ... 0578001095
I've successfully fitted one of these.

After fitting a SD1 dissy my rev. counter went funny, and getting more erratic all the time.
You need to be able to use a soldering iron, and input a signal from a sound source to calibrate,
but all do-able.

I am at the beginning of a RVI to RVC conversion of a P6 Series One Smiths tacho, The first issue is how to get the bezel off; soaked it in penetrating oil, heating on a stove, stretched the bezel rim a bit with a screwdriver next trying to turn it to and fro by hand when that failed clamped with grinding paper in a vise then by a large cloth covered pipe wrench (dont worry it survived; ), to get tabs in line with the slots, I guess. Is that correct ? If its impossible to turn the bezel what could by the issue ? and what the solution ?