Front wiper relay diode

Front wiper played up over the weekend (not parking itself on intermittent or flick) so thought I'd pull up the circuit diagram in RAVE and mug up before I tried any fault-finding (disco is 51 plate TD5).

To the chase: there's a diode G126 in the circuit diagram which seems to connect the park switch to the input of the wiper relay, but I can't find mention of it in any of the RAVE commentaries.

It looks like the design intention of the diode is to energise the wiper relay whenever the wipers are not parked, anyone know for sure either way?

That's an awkward bit of wiring diagram to look at and try to work out what's going on.

There are generally two reasons for a diode turning up in a relay circuit:

1. Current steering, which would apply in the way that you're thinking.
2. Back emf suppression; when a relay is de-energised, it tries to oppose the collapse of the magnetic field by generating it's own "back emf". This can often upset the operation of accompanying and more sensitive electronic components and circuits.

Sorry I can't be of more help.

ISTR that some wiper motors (don't know about the Disco) short out the input to earth when switched off so that the motor acts as a generator to slow it down (like regenerative braking).

Probably entirely spurious in this case.....