How alter a tachometer to function with electronic ign.

[tdafforn]

Hi Guys,
A few weeks ago my smiths Tacho (RVI) died after a long battle with the electronic ignition I had on the car.
I looked at altering the tacho to make it work with the ignition and found that you had to pay someone loads of dosh to do it..
(I don't like 1) trusting bits of my +2 to third parties 2) paying money)
So I have been looking at how to do it myself. I have now managed to do it for the cost of 10 pounds...
Here's how...
My plan was to swap the insides from an RVC Smiths tacho (different internal gubbings that works with elec. ig.) into my +2 RVI tacho caseing.
Unfortunately there are 2 troubles with this
1) not many smiths RVC tachos go to 8000RPM, most stop at 6000RPM
2) not many have the same angular sweep so that you can use the original dial.
After a lot of EBAY watching found a match (RVC 1003/02F) and bought one for 7 pounds!
To put this into the orignal gauge can you nave to do a few modfications
1) strip out the insides of the orignal and new gauge.
2) take off the old gauge face and drill two new holes to mount the new mechanism, cover theold holes with 2 drops of epoxy and paint, matt black
3) attach the new mechanism to the old face ensuring that the cicuit board with the 3 wiring connectors is rotated so that it lines up with the hole in tha back of the old can.
4) line up the new mechanism + old face with the old can and mark where the old can needs cutting to allow the new connector to sit properly. (this is the only more major alteration you need to do to the old gauge.)
5)enlarge the old apperture to allow the new connectors to fit.
6) drill a hole in the can to allow the mounting screw (that holds the new mechanism to the old can) to be fitted.
7) assemble the gauge (old can, old face, old needle, and new mechsnism)
wire into the car (you need a +12v and 0V feed which is the same as the old gauge as well as a third feed from the -ve side of th coil)
9) have a beer
The new guage is much steadier than the old one and works beautifully with an Aldon ignitor


Hope this helps someone else and saves them the 130 pounds I was quote to have it done by a third party!

Cheers
Tim

PS next job, finding a feed so that my turnlock can interface with my MP3 player

[reb53]

Sounds like an excellent idea.
Any idea what sort of cars had RVC 1003/02F tachos in them?

Ralph.
71 Sprint.

[tdafforn]

Not sure...
Unfortunately.
There have been three on EBAY in the last 2 weeks..
Tim

[Jason1]

Tim

I am interested in your mod as my rev counter is not great with the electronic ignition. I have had a poke about on ebay and the Smiths rev counters that go to 8,000RPM all seem to be early Mini's

Now comes the interesting bit, how does the early mini rev counter differ from the one we have on our cars as standard? Mini's only got electronic ignition in the early 80's so these gauges would have been working with points like our cars. So if the ignition system is of the same style why does the new gauge that you put in work any better???

If you can tell me why, maybe I can alter my current gauge without having to buy a new one and replace the insides

Hope you can help

Jason

[tdafforn]

Hi,
The key thing is to get the serial number that is written on the dial..
The +2 one is RVI whereas the one you need is RVC...
As far as the Mini goes I saw those gauges, but didn't manage to get a serial number on them
Tim

[mabink]

Here's a link to the British Car Forum.

http://www.britishcarforum.com/lore/article.php?id=063

To the bottom right of the web page is an attachment, which has a pdf file, and shows how the author has fitted modern internals into an old smiths tacho - plenty of pictures and instructions.