Tach wire on W111 280SE 3.5 ?

[sjefke]

So I have been running my coupe on a Petronix system with Flamethrower coil for a while. It runs great, but because the swicthgear is completely out of the loop, the tachomoter does not work (no signal). I have been reading the various post about adding a resistance in the tach wire to compensate for the 3V switchgear to 12V Flamethrower difference. The problem is that I cannot even get out of the starting blocks because I cannot find the tach wire in my coupe. It is not in the wiring diagrams anywhere. The tach is not even listed in the diagram!!

Can anybody tell me where the feed wire for the tach is in a W111 280SE 3.5 coupe/cabrio??

Thanks,

Bert

[Tony H]

Hi Bert,
I had the tach working on mine when I had the Pertronix. i will take a look this weekend and let you know. I can scan the wiring diagram next week if you need.

[sjefke]

Tony,

That would be great.

Right now I have the red and black of the Ignitor hooked up directly to + and - of Flamethrower coil. I have the coil fed with 12V by a wire from the ingoing terminal of the first resistance to the + of the coil. I have all old connectors to the original MB coil disconnected, so only the ignitor wires are connected to the coil. Works like a charm and is an extremely simple setup.

But somewhere I need to be able to get a signal for the tach, which as said is problematic if I don't know the tach wire

Thanks,

Bert

[Tony H]

I do remember the tach wire was connected to the coil in the original configuration so it should be in the area-probably disconnected. I connected mine directly with no resister and had a slight flutter at idle but otherwise normal operation.