mk triton windscreen washer wiring

[greybeard]

Got a fault with my mk triton 2.8t windscreen washer.
I'm chasing either a wiring diagram or info regarding windscreen washer electrical circuit. specifically if there is a relay in the circuit or not.

The washer motor runs and pumps water ok if I hard wire it to 12v.
With the washer motor disconnected(ie no load) I get power when I activate the washer/wiper stalk as expected. Although the voltage is slightly lower than I would expect. With no load I'd expect to see essentially battery voltage across the washer motor connector.
Measuring the voltage on the washer motor (ie under load) I'm only seeing ~0.5V. This is measured across the actual motor terminals.
This all suggests to me that there is a high resistance/dirty connection somewhere in the system that is causing a voltage drop under load that is preventing the washer motor from running.
Hence the info request to see if anyone knows if there is a relay in the circuit anywhere.
cheers
Rod

[greybeard]

Bit of feedback on what my problem ending up being for anyone else who may have a similar problem.
And yes, it took me awhile to get sick of it and finally fix it.

First off, unplug the wiper motors under the bonnet on the wiper motor so you can test without scraping dry wiper blades across the windscreen.
Lift out the washer bottle, unplug the wiring. It's a little fiddly, there is a push in latch on the side of the plug and the outlet hose doesn't have much slack in it.
Carefully check the polarity of the pump motor connections and using a couple of small clip leads apply 12v and see if it works. Mine did so it wasn't a pump problem.
I went through the process of checking for voltage and voltage drop to the connector and determined that there was a very large voltage drop. ~1v drop with no pump connected and pretty much 12v with the pump connected. I then checked the switch resistance when closed and it was ~40ohms rather than the ~0 ohms I expected. Apart from checking if the pump motor works, the rest of my diagnoses could be bypassed as it was a bit of stuffing around and requires some electrical knowledge.
I then looked at the actual wiper switch on the steering column to check it out.
A bit of stuffing around to access it, had to remove plastic cover under the dash then the cover around the column switches.
The plug on the wiper switch stalk has another of those catch things on the side but mine came of easily. Two screws hold the switch onto the column.
With the switch off I opened it up, two more screws and a push on lug. Inside are several copper tracks and a copper wiper. My problem was the grease spread out over the contact surface. I used some cotton buds, tissues to clean it off and then lightly scraped the contact surface with a small scalpel blade.
Reassemble the switch and reconnect to plug and test if the washer works.
Mine did.
Put everything back together again.

The circuit for the washer is on the same circuit as the wipers. So if they work then the power is ok. If the wipers start automatically when you press the washer stalk then the switch works (but maybe only partially as mine did). If the pump works when there is 12v applied direct to it then it pretty much only leaves the wiring between the switch and the pump or a high impedance switch. There isn't anything else in the circuit.


Sorry there are no pics but I've reassembled it before I remembered this thread.

Don't forget to reconnect the wiper motor.
PS The reason the washer switch seemed to work and turned on the wipers is because the electronics in the switch housing only needed a very small voltage to turn on the electronics for the wiper motor. The electronics turns on the wiper relay.