Tacho for a rd28 to TD42 conversion

[jaido]

so ive read countless threads on this and havnt really gotten the answer im looking for, Im wiring up my tacho coz its finally giving me the chits

so ive got the sender that is on top of the timing chain, ive following the wires coming off that and it goes to this plug


ive then traced that plug and it ends here


so now where do i wire it up from there, my workshop manual only has one small schematic on the tacho and it doesn't tell much




Ive read about how the TD42 has two wires from the tacho while the RD28 has three. The RD28 has two earths and one power for the tacho, and you just hook up the two earths to the single earth on the TD42 tacho and it will work.

where do i find these 3 wires, or has my auto sparky chopped them out when i got him to do the wiring on my conversion last year.