OK. All tests done.
Disconnected power side of relay. Still flash from dash.
Disconnected horn side of relay. Still flash from dash.
Ok we will say that these two are Ok.
Relay clicks when only connected to horn switch. Still flash from dash.
I guess you mean that you only have the two original horn connections on the relay coil now, seems to make sense and ok.
Took wLH control apart - connections look fine. I have no idea where the 8 black ground connection might be found.
I think this connection is half way down the wires from the LH switch to the headlight housing, I found it there when I repositioned my indicators from the bars to my light bar. you could check the from theb awitch to the connector in the headlight.
No flash from any indicators or any other light except 3 dash lights ...
the red oil light on dash, green indicator light on dash and green neutral light on dash.
Possible cause ...
These three dash light were replaced with LEDs. Could the sensitivity of the LEDs be activated by something really minor?
The LEDs draw less current that the bulbs so it might be worth checking all your earths, the other thing is the indicator lamp polarity changes depending on L or R is switched, I dont think you can put an plain LED in there. try swaping it back to a bulb.
I have run out of time tonight so haven't checked the dash wiring loom yet.
I cant view your diagrams from this PC but they sound the same.
Sleep well.