Wiring help

[thackers]

Hi could anyone please help with a problem I have wiring up a koso rev counter? To change the current from DC to AC I've been given thiswith the instructions of red is 12V+
Yellow x2 to AC either way
Grey is OV
The Rev counter has wires
Red 12 v DC
Black earth
Brown to ign switch (not applicable)
Orange to H.T lead
Can someone tell me how it all goes in numpty terms so a thicko like me understands. Thanks

[Nerdy Norm]

Not exactly sure what you've got there, but I wouldn't trust the electrical skills of whoever gave you those cables!

The first pic looks like it might be 4 cables joined together and stuffed into a fuse holder. Not sure how that will convert AC to DC.

The second looks like someone's chopped off the multi-plug and had a bash at crimping on a big connector onto a thin wire - I don't think it will last long. If I were you, I'd get some proper connectors and start again.

This is probably where the tacho wires need to go:
Red 12 v DC (correct)
Black earth (correct)
Brown to ign switch (not applicable) (join to red, it will need to be powered - bear in mind that if you have a battery, the tacho will be permanently on)
Orange to H.T lead (I'm guessing it's the sensor wire, in which case it needs to connect to an 12V AC supply, perhaps your headlight)