I have a 4K VDO tach here from parts unknown. It has 4 male spade connectors on the back. I suspect it is a Diesel tach because it only goes to 4,000, but it could be a boat tach. It was in a 75 Chevy truck that I found butchered in a boneyard and I’ve seen it ALL under the hood so who knows.

The 4 spades
1. = + and I know that is power.
2. = S
1 ‘S’ over #1 ????????????
3.= has the Christmas tree and I know that is typical electronic hieroglyphics for earth ground.

4.= is the ‘S’ again with a Christmas tree.


So #1 & #3 I have figured out, but what the heck is #2 & #4 all about? Does the ‘S’ stand for SIGNAL?? And why a signal with a ground? .

SO I can't find a TRUE VDO website either-just posers. I want ot find out what else i need to make this work.
Thanx , crossy

 

I, too, am interested in this.

The wife's truck came equipped with a VDO tachometer, complete with digital LCD hour-meter readout (the tach has a needle).

This tach is somehow hard-wired into the alternator.

Recently, it just quit working, and I haven't had time, nor kept her still long enough, to diagnose the problem.

 

It might be a marine unit. My boat has all VDO gauges. The tach is run off a sensor that is a engine specific in my case. I have a Mitsubishi. No idea how its wired.

 

I just installed an autometer tach in my truck. It came with a pickup that straps to the outside of the alternator. There are two wires that come from the pickup and go into the tach, so I would guess it needs a positive and negative signal wire. That's just my guess though.

bearkiller, on yours I would guess that the tach is wired into the "w" terminal on the alternator. I believe there is an article in the sticky on how that works, but I might be wrong.