Weird rear wash/wipe issue??!

[Davey Blueeyes]

Okay, rear wash wipe works just as it should. Let's get that out of the way! 

However, completely randomly, the rear wash 'leaks' screen wash. It's a bit more than a leak, a steady trickle but not as powerful as the actual wash? It does this totally randomly and only stops when I either turn the car off or run out of screen wash! 

Bit of a pain in all honesty but no idea how to start solving it?? 

[m4rkw]

Can you see where it’s leaking from? Are you sure it’s completely random or is there some pattern to it, like just after you’ve used the washer, or when going up or down a hill?

[Davey Blueeyes]

1 hour ago, m4rkw said:

Can you see where it’s leaking from? Are you sure it’s completely random or is there some pattern to it, like just after you’ve used the washer, or when going up or down a hill?

I've attached a very dodgy video of it do it. Only started this week while I'm away. I last used the wash wipe about 4/5 days ago and first done it about an hour after that and emptied the screen wash. I topped it up three days ago to the top and I haven't used the wash since (i have just wiped a few times to clear the rain off) but today on the motorway it just randomly started doing it again until it fully emptied the screen wash. 

If the video loads properly you'll see it doesn't come out as strong as the wash does but it's more than a trickle

Any and all ideas are helpful! 

[Sherra]

Possibly syphonic action?

[Texas]

That's proper weird! Gonna cost a fortune in screenwash. Does it only do it when you are above a certain speed? What starts it off?

I would try and disconnect ( electrically, either fuse or pull plug on pump if you can get to it) the rear wash to check if it is the pump or some spooky syphonic action at speed! 

[Herbie]

Can't be syphonic as the height of the nozzle is way above the height of the tank.

Water cannot climb uphill on its own so it has to be an electrical problem running the pump (front wash and rear wash have separate pumps if I remember correctly) but not at 'proper' speed.

Auto electrics are like the black arts. I remember working on a skip truck* whose very perplexed driver brought it into the garage and said, "Watch this." Every time he pressed the footbrake the windscreen wipers did one full sweep! We traced it back to a partial short circuit where the wipers were getting a backfeed from the brake pedal switch.

*I was an apprentice electrician at the time, in a factory. I don't know why they did it but the 'powers that be' decided it would be good for the apprentice electricians to get a bit of experience in the factory garage, working with the auto electrician for a month. Have to say I did enjoy it though 🙂

[Sherra]

Agree Herbs second guess sticking relay?

 

[Herbie]

6 minutes ago, Sherra said:

Agree Herbs second guess sticking relay?

Possibly Paul, although I don't know for sure if the washer pumps even have a relay in circuit.

[ColinBarber]

No, the washer circuit doesn't use a relay, it is directly powered.

You can pull the Washer fuse to prove it is an electrical faulty - the single fuse protects both front and rear washers.

It's a weird fault but the wiring for the rear washer is quite simple so it is either a fault with the wiper control stalk or a wiring issue. The design of the circuit means there is a 12v feed on the pump at all times when the ignition is on so it is possible that the return could have a high resistance path to the vehicle ground which would give you low speed running of the pump - e.g. the connector is damp/wiring insulation damaged etc.

[Davey Blueeyes]

Thank you all, I really appreciate your responses for my weird fault! 

I didn't realise there were separate pumps, makes it easier in some ways. The front wash wipe does its thing perfectly. Well to be fair the rear one does too! But it also does this! 

13 minutes ago, ColinBarber said:

No, the washer circuit doesn't use a relay, it is directly powered.

You can pull the Washer fuse to prove it is an electrical faulty - the single fuse protects both front and rear washers.

It's a weird fault but the wiring for the rear washer is quite simple so it is either a fault with the wiper control stalk or a wiring issue. The design of the circuit means there is a 12v feed on the pump at all times when the ignition is on so it is possible that the return could have a high resistance path to the vehicle ground which would give you low speed running of the pump - e.g. the connector is damp/wiring insulation damaged etc.

Great knowledge right there. It's (luckily) a relatively simple part of the electrics so possibly worse case scenario swop out the rear motor washer/wiper control stalk? Or maybe try cleaning it all up and checking the insulation? How hard is it to access the two motors?? 

Again, thank you all, much love

[ColinBarber]

Not sure how easy it is to get to the pumps, normally the reservoir is in the wing so it is either front wheel off and remove the wheel arch lining to get to it, or worse the front bumper has to come off. Have a look in the engine bay to see if you can see them.

I'd start with the switch, you should be able to narrow down where the fault lies from there. If you disconnect the wiring connectors from the stalk then measure the resistance between pin 5 of connector A and pin 2 of connector B. It should be infinite and then approx. 0 ohms when you move the switch to wash. If you have a reading other than infinity when the switch isn't being moved to wash then that may be where the low power is being supplied to the motor and the switch is faulty.

If that is ok then measure the resistance across those two pins but on the plugs rather than the switch - you are then measuring the resistance between one side of the pump and the vehicle ground - if you have anything other than infinity then you have a resistance path in the wiring somewhere or at the pump connector.

I cannot see it being the pump itself as that probably has plastic body and mounted on the plastic reservoir and therefore has no direct connection to ground to complete the circuit itself.

 

Connector A

 

Connector B