Dumb Tachometer question ?

Elombard · 09-27-2004, 02:44 PM

I won a 964 tach on ebay for super cheap. My Tach quit working and I thought this might be an interim step until I can afford the real one. Any body know if a 964 tach can be made to work with the out put from a 79 SC?

Thanks

pookie · 09-27-2004, 04:44 PM

Do you have a pic of the back of the 964 tach? I just put an Autometer tach in my car, and did as much research on it as possible before I installed it. I might be able to tell you more, but I've never seen the back of a 964 tach.

rattlsnak · rattlsnak's Garage

Dont think it will work. Yours is CDI, the 964 is DME. Plus, it runs through a "dash module".

Elombard · 09-28-2004, 03:59 AM

Well at least it was a cheap experiment :-))

Here are some pics. The diagram on the back uses alot of the same letters as my old tach (Td etc.). Wonder if it would hurt anything to plug it in?

Elombard · 09-28-2004, 04:03 AM

Also, any body know what Fernlicht is?

I think

KL.15 = power
KL.TD = tach signal
blinker rechts = right blinker
blinker links = left blinker
KL.31 = ground???
instr. beleuchtu...=instrument back light
Fernlicht = ??? light

masraum · 09-28-2004, 05:33 AM

Fernlicht -- high beams

Rich76_911s · Rich76_911s's Garage

If you are interested in selling the tach let me know the details at rmshaner@hotmail.com

pookie · 09-28-2004, 09:05 AM

I don't have it in front of me but on the back of the tach in your car you should have 3 small male plugs on the bottom of the tach, which will be labeled "+12", "td", and "-". On my car I reused the +12 as power, and - as my ground, but I had to run a new wire from my ignition box to the new tach. Also there will be seperate wires near the top of the tach that run to the lights of the tach, and the high beam lights. If it was really cheap and you don't care if it gets damaged, I would figure out which wire is which and hook it up. What ignition are you using? That may be a factor as well. I would also consider what Rattlsnak said. If you have an aftermarket ignition like MSD or such then I think your chances of it working may be greater.

Early_S_Man · 09-28-2004, 09:33 AM

Erik,

It looks like you have the label nailed down ... now just figure out the color code of the wires in the cable that was chopped off at the dismantler ... and you will be ready to hook it up and give it a try!

My suggestion to make it work with the six-pin Bosch CDI unit is to incorporate a 1 Watt 1000 Ohm pullup resistor into the spliced cable assembly ... between the +12 Volt power lead and the TD signal input lead. The CDI TD output lead has a diode inline internally which only allows current-sinking ground pulses ... and the pullup resistor is needed to 'pull' the TD signal into the tach 'up' to +12 Volts when the ground pulse signal isn't present. You might even try your old tach with the resistor mod ... it might work after all!

Elombard · 09-28-2004, 11:11 AM

Thanks Guys I will give it a whack. Warren I will try your mod first with the old one. Will Radio Shack have that or should I look somewhere else?

I am running a stock 6 pin. I wonder if the Tach signal thingy that MSD sells would work with the CDI - I guess I should just go back with a stock unit before going to all that trouble.

Thanks again - this place is amazing.

pookie · 09-28-2004, 11:40 AM

I had another thought as well. You may have to check with Warren on this one, but if you are worried about frying the 964 tach when you hook it up couldn't put in a small fuse between the power and the tach when you hook it up? Would the fuse blow before the tach, therefore saving it from any damage? Like I said I'm not sure about that one, but thought it might help.
Ryan