Porsche tachometer

[SilverBullet]

I've installed a 914/4 tachometer and every time I turnoff the ignition key, the needle deflects quite a bit, otherwise it works well! Why?

[beetle1303]

Since its from a 4 cyl its fine (silly) it might be a bad connection? Something close to the ignition key perhaps ( the tacho gets energized at the 2nd position...). It could be at the coil's connections?

And what do you mean by deflection? Mine (sunpro) drops from 1100 rpm to 200 rpm and then goes straight to zero (at the support).

Chris

[SilverBullet]

Usually, from idle to 0rpm, but the needle deflects to about 5-6k rpm then 0, some times 3-4k rpm. I've check the connections but can't seem to find anything wrong, I check again.

[SilverBullet]

Still the same!!

[zen]

Mine will drift under quick throttle changes, but nothing when turning off.

[LLVWGL]

I would guess that you could possibly eliminate this by upgrading your spark plug wires. I say this because if you have a poorly insulated coil to distributor wire, you could be getting a surge transfering to your ignition coil power wire through electronic induction. The coil is a large capacitor, when you remove power from it, it discharges. You may need to just make sure that your coil power wire and your main distributor plug wire are farther apart. Do you have them zip-tied together? You could also add a diode inline on your ignition wire that would prevent any power from coming back up to the tach.


hope this helps.

[SilverBullet]

Thanks for the reply, will try and separate them.

[krazz77]

Hi SilverBullet,

If i'm not wrong, you are from Singapore right? Are you still facing the problem? I installed mine and it works just fine. I think I connected to a '1' on the ignition coil.

Regards,
Danny

[Steve C]

Hi

I had an old Stewart Warner tacho that originally only used - from the coil and an earth, when I had it converted to run with electronic igntion and EFI it would do the same thing on shutdown. I imagine its caused by backfeed.

Steve