John07, yup have seen opto isolation used to protect PLC`s from spikes etc.etc.etc. but more than happy to have left all that behind when I retired and have none of it in my old non digital Morgan...(-:
Jads/John, sorry if I may have mislead you, I am out of date in so much these days, from that which Colin typed it seems colour coded wiring may be like me... a thing of the past..
Glad that you resolved your issue by identifying the relay location. Given the replacement and re-flashing costs (ouch!) I can understand why you want to be sure there is protection built in to the relay, even if there is already protection on the ECU outputs.
