I am pretty sure that the late series over-drive relat has an in built resistor to reduce the current to the solenoid once engaged. The purpose being to stop it burning out. Check out the wiring diagram for a series 5 and you will see a resistor drawn. A cheap item from Radio Shack but its worth remembering as the solenoids are not so cheap.
The actual wiring is pretty straight forward.
>The relay setup can be made from a couple of $3.00 headlamp relays if
>you are not concerned about origionality.
>
>John.
-- Jeff Howarth