|
I've the same additional fan in my smugglers box of my '68 912 and if I'm right, the relay is for driving the fan motor. The fan was an option, like the Webasto heater, and therefore not found in the wiring diagram. The relay is usiualy mounted under the dash, just behind the fan and fog light switches. The fan switch is also situated in that area. Check/replace the relay. The noise could be caused by a bad ground/earth or switch contact.
The yellow relay is indeed likely the fog light relay. The yellow relay is used to enable the fog lights to be switched on only when the low (or high) beam is switsched on. In many countries it is/was not allowed to drive with only fog lights on. They only where allowed to be used in combination with the H/L beam. Perhaps this is the reason why the fog lights did not function as you expected. So first turm the H/L on. The relay switches +12 V to the fuse box, where two green/white wires are used to feed the fog lights.
Looking at the picture the second relay is indeed not connected. It would be guessing what its pupose was. It is not a more or less standard mod/addition.
Regarding the green wires I would say: look at the other side of the tunnel and check where they end. Could it be that they are to be used for the oil level sender? At least one of them? Oil pressure and level are both green with a colored band.
I hope this helps a bit in solving your wiring problem.
Otto
|