Volvo Tachometer wiring question induction sensor style

[Mr Googler]

Hi all

So…after much digging I’ve hit a dead end

I’m wanting to replace my tachos and obviously went cheap Chinese route. I bought a tacho that can handle induction sender (I even know the tamd61 flywheel has 141 teeth for setting the ratio. Problem is…..the flywheel sender has 2 wires…..new tacho just the 1 for signal.

My current tacho looks like this


Internet photo but the same. Mine has an extra pin outside the main block which is to power the needle back to zero



So on looking at the wiring diagram. I have black, blue/red, grey and grey black



Now, what I can’t figure out is what grey and grey black do (S+ and S-)

Does one stick 12v to the sender and the other read the pulses coming back? Voltmeter back me nothing volts wise to ground with the key in start position.

My new tacho is wired like this



So what I’m after knowing is which of the grey wires does what. If I know that I could put one the VE+ or VE- and put the other to the signal input. Just need to understand how the magnetic induction sensor works! Please let me know if I’ve got the wrong end of the stick on how this all actually works

 

[PaulRainbow]

One wire to the sensor goes to VE- the other to the signal input on the tacho.

Can you not connect the tachos to the alternators ? I fitted KUS tachos to my lower helm and one of them didn't work very well on the sensors, but they both work perfectly on the alternators.

 

[Mr Googler]

One wire to the sensor goes to VE- the other to the signal input on the tacho.

Can you not connect the tachos to the alternators ? I fitted KUS tachos to my lower helm and one of them didn't work very well on the sensors, but they both work perfectly on the alternators.

Thanks Paul. I just read it doesn’t matter which way round the sender wires go. Is that right?

I’ll try this and swop to alternators if I have no luck

Given grey goes to G (for gauge) I’ll put that on the signal input and ground the other

 

[PaulRainbow]

Thanks Paul. I just read it doesn’t matter which way round the sender wires go. Is that right?

Correct

I’ll try this and swop to alternators if I have no luck

Given grey goes to G (for gauge) I’ll put that on the signal input and ground the other

Why not