SAme old chestnut..........................

[mark030358]

sorry but ............my tacho. Converted to RVI by speedy, Aldon ignitor fitted and +12v supply to Ignitor direct from fuse box. Tacho still won't work properly, swings wildly and wont read over say 4000 rpm. When injected with pulse generator all is ok.

Any ideas???

thanks
Mark

[rgh0]

3 things I would check for what they are worth.

Where is the tacho getting it 12 V supply from and is this a stable supply point when the engine is running. Try a connection directly off the battery if unsure.

Where is the voltage pulse signal wire for the tacho connected to, it should be the negative side of the coil that goes to the distributor

Is the tacho properly earthed. Not familiar with the conversion but did they include a specific earth connection to use or did they earth it via the case. The earth point used to the chassis may be marginal and you could be getting a problem when other loads are applied to this earth point with the car running.

regards
Rohan

[mark030358]

Fixed my tacho bounce. After conversion it still bouced around. Tried seperate earths and +12v feeds but no joy. In the end ran a shielded (and earthed at source) cable from the coil to the tacho and now its OK (fingers crossed). Must have been picking up voltage spikes from the HT system.

cheers
Mark

ps voltage spikes should not affecy a current impulse tacho though