Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Rev counter

I have a 1976 +8 , the rev counter has just been altered for electric ignition , i have a yellow wire to go to the coil .
But what side of the coil ?
Please help…..

Don't know which system you're using but the sensing wire to the coil will want to see the pulses from the trigger to the coil so will go to the side that connects to your distributor rather than the +ve feed

K

I believe the Smiths RVC tacho works as Image suggests. However the GoMog wiring diagram that covers +8 from 1977 onwards shows the white ignition switch wire passing through the tacho then to the coil with no other trigger wire shown. In this way it can pick up the ignition coil current pulses. I guess it depends on the type of tacho you have though.

If it's 'just been altered' suggest you speak to who did the conversion, as depending on the electronic implant they don't all use the same 'trigger' and you don't want to pop it - mine had to be re-calibrated using a programme they sent me via my laptop

There are 2 types of rev. counters RVC and RVI. One senses voltage pulses and the other type current pulses. In my (naive) world there should be no change at all on the rev. counter if you are still using a single ignition coil, because the electronic ignition does nothing else than interrupting the current flow to the coil like the mechanical contact breaker within the distributor would do. Can you provide additional info regarding the electronic ignition and rev. counter ? Maybe these links may help

https://spiyda.com/tachometer-wiring
https://www.gomog.com/allmorgan/smithsclassic.html

That info agrees with the diagrams I've seen Cerberas. The earlier RVC type tacho (used up to 1976) accepts a voltage trigger and connects to the contact breaker side of coil. Addition of electronic ignition to replace contact breakers should make no difference as long as tach trigger remains connected directly to coil CB terminal.

The RVI type uses current to trigger. Typically a couple of white wires on tacho accept feed from ignition switch and onto coil positive. A small shunt connects internally to the wires to sense coil current and so provide trigger. Again addition of electronic ignition should make no difference.