Windscreen washer gremlins.

[Doobit]

Driving in the rain today, wipers were on, and suddenly the windscreen washer switched itself on permanently and was only squirting through the right side jet. Switched car off and on and it was still going. Then it switched to left side jet before discharging a full tank of washer fluid. Any idea where to start troubleshooting? Switch on the column, relays, or pump motor. I have wires leading to the washer jets but I've always assumed they were heaters for the jets rather than any kind of switch.

[Brianmoooore]

Wires to the washer jets are heater wires.
I'm assuming it's the normal screenwasher that's playing up, not the intensive wash.
12 volts ignition switched power is permanently applied to one side of the washer pump, and the pump operates by earthing the other wire by the column switch. No relays are involved, although there is a connection to the wiper control module, which allows the washer switch to also control the wipers.
It's very unlikely that a fault in the module itself would switch on the washers
First thing to check is that there's not something metallic that has slid under the wiper control module in the fusebox, and is shorting the washer input pin to the earth pin - surprisingly common.
If everything is OK here, then the wire between the pump and column switch is being shorted to earth somewhere else, probably at the switch itself.
The pipe from the washer pump to the jets goes to both jets via a tee piece, so any issues you had with one jet working and the other not is an entirely separate fault, and will be blockages in the jets.

[Doobit]

Thanks Brian, so fuse box check first. Then the switch, then the wiring. Much appreciated.

[Stefan on probation]

I had the same issue a few years back and it was a faulty stalk, driving home on the A3 on nice early evening I dumped a full tank of water, I don't think the drivers behind me where impressed.