The 156 headlamp wash timer relay
If your 156’s headlamp washers have stopped working, it could be that the timer relay has packed up; mine did, repeatedly. I was able to get it working again quite easily, here’s how.
First, test the headlamp wash pump by swapping its connector with the screen wash pump, if it’s working now then your timer relay could be faulty. Remember to swap the connections back!
Now for the hardest part of the job – getting the relay out of the dashboard. It can be accessed through a hatch in the top of the glovebox but removing the whole glovebox makes things easier. If you do go through the hatch, you’ll have to remove another small relay first; make a note of the orientation of this and the timer relay, a bigger black cased relay. I wrapped a long length of tape around the timer relay so it was easier to hold during reinsertion. You don’t want to drop it or you’ll be removing the glovebox anyway.
About the relay: Bosch part no. 1397328006, it has 5 terminals:
30 – ignition switched supply
31 – earth
56 – 12V when side or headlights are on
S – 12V when screenwash is on
P – switched power to the headlamp wash pump; normally shorted to 31, switches to 30 for about 1s when 56 and S are 12V
I bench tested the timer relay by connecting 31 to earth and 56 to a 12V supply, touching S to 12V should make the relay click on for a second then off again. If it doesn’t click then open up the relay and inspect the circuit board. Mine had bad soldering on the legs of a rectangular capacitor in one corner of the board, resoldering this got the relay working again but it was only a temporary fix until I fully removed the capacitor (it was glued down), cleaned and tinned its legs and refitted it.
Sorry, no pictures as I don’t have my 156 any more; I just stumbled across the notes I took about the relay last time I repaired it and thought I’d record them here for posterity. Hope this helps someone.