Anyone know the pinouts of the SAV tacho?

w5yk · Post by **w5yk** » Thu Dec 06, 2007 6:55 pm

Anyone happen to know which pin is which on the VDO tachometer?

Mine is reading low, and I found that only two wires are hooked up. The terminal closest to the drivers side is connected to ground. The next one is connected via a resistor (in white heatshrink) to the coil, and the third one is not connected. I assume that the resistor should be used in series with the 24V connection to drop the volts down to 12V, so a previous owner presumably hooked this up wrong by putting it on the sensor line to the coil. I put an oscilloscope on that line, and I have a nice square wave on it that goes up and down with engine revs.

I assume that the gauge is being powered (not very well) via the internal clamping diodes on the input, and that is why it works at all. But I bet it would work a lot better if I actually connected 12V to it. Which terminal would that be? Presumably the third one, closest to the passenger side?

Any info greatly appreciated,
Richard

lindenengineering · Post by **lindenengineering** » Thu Dec 06, 2007 7:30 pm

Richard
Just happen to have this info on hand.

Going from left to right looking at the bottom (from the back) of the guage we have thus:-#2 IS SENSOR, Middle connector is +Ve and has the resistor, and lastly the other connector is -Ve or ground know as "earth" in the hallowed isle. Remember the sensor MUST be connected to +Ve at the coil. That maybe your area of concern reading your post--OR that the coil is hooked up backwards.
Hope that helps
Dennis

w5yk · Post by **w5yk** » Thu Dec 06, 2007 9:26 pm

Thanks Dennis. That's exactly what I needed to know.

Mine is hooked up wrong, as I thought. Easy to fix in the morning.

No problem decoding your English (being from Belfast myself).

Many thanks for the quick reply.