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Sun Jul 31, 2016 10:50 am

I installed my tachometer today which came from my previous bug and worked fine but now in the new bug it's giving me wrong readings.
The needle is floating up and down in the 1500rpm area while the engine is idling. I have a new blue bosch coil and hooked up the cable to the - pole.

Any ideas what this could be ?

Sun Jul 31, 2016 12:23 pm

Have you installed the diode?

Mon Aug 01, 2016 4:04 am

No I didn't installed the diode and didn't install it in the previous bug either.
What kind of diode do I need to install ?

Mon Aug 01, 2016 4:32 am

i never installed a diode in mine either, is it grounded correctly? i had this issue too before and it was the ground...

EDIT: and is the condenser grounded properly? i also had a problem before that the tach was fluctuating so much, it was the condenser ground...

EDIT again, sorry: might it possibly be that you started the engine cold and the choke is on and the rpms are really at 1500?

Mon Aug 01, 2016 4:35 am

I will check that today and clean the ground attachment with some sandpaper.
Thanks for the tips

Wed Aug 03, 2016 1:28 pm

I attached a new connector on the cable coming from the coil because the cable wasn't seated really great. When I started the engine it was around 1000 rpm which seems more correctly with the choke still on but the needle was still floating up and down.
I found a video where they fix this issue on a autometer gauge with a 10K 1/2 watt resistor. Will this also work with my vdo meter ?

EDIT : It's a new condensator and directly connected on a new coil. I assume there is nothing wrong with those :)

Sat Aug 27, 2016 1:34 am

I added the resistor but didn't do anything.
Can someone tell me if my rpm gauge is broken or is my engine really running to high ?

Sat Aug 27, 2016 3:45 am

Make sure the dip switches are setup properly. If it is like my bigger VDO tach there is a little rectangle on the back that has the three little switches in it. You need to set it up for a four cylinder engine. I had to set the dip switches on my tach not to long ago… It took a few tries to get it right.
http://www.nzjetboating.com/yabbse/index.php?action=dlattach;topic=17109.0;attach=30418;image

I am guessing yours looks something like this:
https://www.vdo-gauges.com/media/catalog/product/c...c_back.jpg

The dip switches are in the little rectangle near the top.

Andy

Sat Aug 27, 2016 5:09 am

The dip switches are correctly setup as in the picture so #1 is on and #2 and #3 are off.
The tacho worked in my previous bug, that's the strange thing.
Can I break my tacho when I put in on 6 cylinders and start the engine ? Think I will try that and see what it gives and then put it on 4 again after.