Autosport Labs

hello all,

I just got a tach adapter for use on my zetec capri, I have a aftermarket rev counter what needs a a signal from the neg side of the coil. Because I am using the zetec red ESC box with the vac take off I am not running a MJ as yet but still need of a rev counter I have tried many way all with no result the best I can get is the rev counter to read half the RPM, so I invested in the tach adapter to solve my problems but with it wired up as the web site says I get noting on the rev counter, but if I take off one of the coils it goes back to reading half. So what else do I need to do to get this to work?

Hello,

Tachometers vary quite a bit in what they need for a signal, and can be tough to get right in some cases.

We designed our tach adapter to follow the widely known diode isolation circuit plus the addition of 100K bypass resistors as some tachs seem to need to see a small constant 12v signal between ignition pulses; the older Porsche 914 tach we are using in our race car is one example.. So, it should work with the vast majority of tachometers out there.

Schematics here:
http://www.autosportlabs.net/images/4/4 ... er_sch.png

What you can try doing:

1. If you have coil 1 and 2 pads connected on the adapter board, you can try removing resistors one at a time to see if you get a signal. If you have a fine tip soldering iron you can heat up Resistor R1, remove it, and test it. If that does not work, remove R2. and try again. This will check if the resistors in the circuit are interfering with the operation.

2. Try adding a zener diode between the tach adapter and your rev counter. Use a 15-18 volt zener diode, with the band pointing towards the tach adapter.

3. Contact the tachometer manufacturer and ask for their technical assistance, describing what you are trying to achieve. It should be a relatively common topic for them.

Please keep us posted on your progress!

so from what you said if i remove these one at a time


i am a complete noob to this kinda thing i am all spanners and hammers

Yep, those are the resistors. Removing those is what we're suggesting, *as a test*. we don't know the tachometer you're using, so it's what we would actually do to find out how to make it compatible.

If you don't have a soldering iron capable of removing those resistors, you can check around your community to see who might help.

Getting these tachometers working can be tricky- and we'll help as much as we can.

cool thanks, i will give it a go and we shell see what happens

right I tried removing one and both but nothing happened the tach did not even move but if i just have the one line in it reads half, so what can i try next?

whoooo sorted i put a 18 volt zener diode after the tach adapter and all works now thanks for your help guys, may a good thing to sell with the kit in the future?

brentp wrote: What you can try doing:

1. If you have coil 1 and 2 pads connected on the adapter board, you can try removing resistors one at a time to see if you get a signal. If you have a fine tip soldering iron you can heat up Resistor R1, remove it, and test it. If that does not work, remove R2. and try again. This will check if the resistors in the circuit are interfering with the operation.

2. Try adding a zener diode between the tach adapter and your rev counter. Use a 15-18 volt zener diode, with the band pointing towards the tach adapter.

I did step 1 with no luck, then added a 15 volt zender diode and it worked. zener diode cost me $0.72.

I agree with mini, for the cost/frustration/convenience factor, it should probably be included in the kit.

to close the loop on this, the 15v zener worked only to 3000 rpm.

18v didn't do anything different.

i ended up not using the tachAdapter, or any MJ signals (none seemed to work). i used the pin 11 on EDIS (CTO - clean tach out)