Another tach installation question

[Ajax]

Gents,

A while back, I purchased a tach without considering whether it would be compatible with an A4.
I know it's not for a diesel because it does have a lug for "IGN" (ignition).
However, I have no idea how many cylinders it may be set up for. It doesn't have a selector switch like an automotive tach (4, 6, 8 cylinders)

Take a look at the photos and tell me what you think. It has been suggested that this tach is meant to be driven by the Motorola alternator.

The tach has "IGN", "GRD" and "B" or "S"...the ink is blurred...not sure what it is.

What say you?


and...

[ndutton]

The tach gets it's signal from an AC (aka stator) tap in the alternator. If you don't have one it's an easy and cheap mod by an alternator shop. Underneath the 'CAL POT' sticker is an adjustment screw. After installation the tachometer will need to be calibrated (the 'CAL') by adjusting the calibration potentiometer (the 'POT'). You will need something like an optical tachometer (a tool) to determine the engine speed and dial in your new tach to match.

[Ajax]

After some digging, I actually found this tach on the internet.
Well, I found a new one for sale on eBay, and found the company on the web.

The "S" terminal is for a "sender". The sender converts a mechanical signal from an engine component to an electrical signal that the tach can read. Like a cam lobe or something.

The eBay ad claims that this tach doesn't require a sender, and that it's compatible with 3, 4, 6 & 8 cylinder engines which would seem to support the alternator hypothesis but I'm skeptical.

I guess I could wire it up and see if it blows apart. I only paid a few bucks for it. FWIW- the tach was OEM for old Chris Craft power boats.