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MJ and tacho wiring
dave1888 - 9/9/07 at 12:59 PM

The wiring diagram for tacho shows the signal (S) should be connected to the negative side of the coil. When using megajolt should i connect the tacho as the attached diagram, if so would i be right in thinking i take a diode from 10 and 12 on the edis unit to the zener diode. Rescued attachment Tach_circuit.jpg
Rescued attachment Tach_circuit.jpg

David Jenkins - 9/9/07 at 01:14 PM

I used the tacho output from the MJ plug - it worked for me, sometimes doesn't work for others. This is with a Smiths/CA/Greengauges tacho.

Worth a try, before you make up the circuit you've described.

paulf - 9/9/07 at 07:50 PM

It is also possible to connect the tacho to the PIP signal from the edis.
I found that the edis tacho output didnt work and used the diode method for a while but had a problem with that after a while.I then connected to the PIP signal and found it to work ok.
Paul.

MkIndy7 - 11/9/07 at 03:58 PM

quote:
Originally posted by paulf
It is also possible to connect the tacho to the PIP signal from the edis.


I've had to use this method on a friends Triumph Spitfire and i'm pretty sure its to blame for strange blips in the map, although the internals of the guage also stick at times.

Quite often when watching the map whilst the car is running it will jump upto around 3,500 revs and its equivalent advance figure.. and then jump back to where it should be in the map, causes a bit of a pop in the exhaust on the over run from a steady cruise but thats all.

So it does work but i'd try it as a last method. That was for a very old SMITHS Guage.

paulf - 11/9/07 at 07:48 PM

That sounds as if it is picking up some interference on the tacho wiring and feeding it in as an extra pip signal.
Ive not had that problem but as suggested it may be best to try the other methods first.
Paul.

quote:
Originally posted by MkIndy7
quote:
Originally posted by paulf
It is also possible to connect the tacho to the PIP signal from the edis.


I've had to use this method on a friends Triumph Spitfire and i'm pretty sure its to blame for strange blips in the map, although the internals of the guage also stick at times.

Quite often when watching the map whilst the car is running it will jump upto around 3,500 revs and its equivalent advance figure.. and then jump back to where it should be in the map, causes a bit of a pop in the exhaust on the over run from a steady cruise but thats all.

So it does work but i'd try it as a last method. That was for a very old SMITHS Guage.