Mondeo Mk3 Estate Earth Points.

[aryan57]

I lost my windscreen washers and its a very frustrating experience trying to track down the fault. I fitted a new pump and checked that the pump runs from a 12 volt supply and it does. I have also fitted a new wiper stalk but still no joy.

The Haynes manual shows an earth point E3 on the "LH rear wing" Do I take this sentence to mean that E3 will be found at the rear on an estate? I have looked at the Front "rear" wing and I cant find an earth point there. Any earth points at the front of the car that I found I have cleaned up. Thank you kindly.

 

[Tigercubrider]

Presumably the switch doesn't control the earth?

So why not just run back to the battery?

My auto - electrics knowledge is poor by modern standards as I am used to old positive earth motorbikes where they used the frame as earth. I would always add an Earth wire as using a painted frame as a conductor was a recipe for disaster

 

[aryan57]

Its a Canbus system. That means that every bit of the car communicates with every other bit so whether this controls the earth paths, I cant tell. I suspect that it does. The clever bit is that the pump can run in either direction, depending on whether it is the front screen that needs washing or the rear.

All the wipers work just fine, even the delay function. All the fuses check out good. I have changed the wiper stalk but no joy. I may go down the road of putting a momentary switch on the dash and rewiring the blasted thing. I shall then only have the front washers but I never used the rear anyway. And rear wash/wipe is not part of the MoT test.

 

[rsgaz]

earth point E3

I'd be very surprised if it is an earth fault, unless a stone/corrosion has damaged just that wire. There will be lots of things earthed at each earth point, so you would be experiencing all kinds of others problems too.

I may go down the road of putting a momentary switch on the dash and rewiring the blasted thing.

If you do go down this route, then by using a double pole, double throw momentary switch, it could be wired so that the pump can still function in either direction and still squirt both screens.

Gaz

 

[aryan57]

Thanks Gaz, I did not think of using a dpdt momentary switch. I will give that some thought. Sounds like I will be able to retain both functions. There is bound to be a snag I have not thought off!

I need to remove the wheel arch liner anyway to deal with a couple of dents, a ladder fell on it and dented the top of the wing. With the arch liner removed there is more room to work on the wiring to the pump. My plan for tomorrow is to check for 12 volts at the pump pins using a test light and moving on from there.

Thanks again.

 

[rsgaz]

The Haynes manual shows an earth point E3

That's a point which has only just dawned on me, if it is a two wire pump which spins in either direction for each screen, then it can't have a direct connection to the chassis negative. There's either a relay for it, or the GEM is providing the positive and negative in either polarity itself.

How is the Haynes manual showing it connected?

 

[aryan57]

 

[aryan57]

Tried to upload the electrical diagram page from the Haynes manual but failed. I have cleaned the earth points under the hood but I have so far failed to find one at the rear. The interior earth points I hope to do today if the rain stops! The Haynes manual shows washer and wipers as 2 separate systems.

Someone on another forum suggested that the car uses an earth switching method, as is common to many Japanese cars. How GEM works? I am in the dark on that one but when it works, it works its magic fine. I feel really out of my depth trying to puzzle this out as I have no training in electrical engineering. I am limited to cleaning connections and replacing parts.

 

[aryan57]

Trying again to upload a page from the Haynes manual. Seems to have worked this time.

 

[rsgaz]

Scroll down to "PINPOINT TEST G"

http://workshop-manuals.com/ford/mo...ion/diagnosis_and_testing/wipers_and_washers/

You're going to have to go through all the steps here with a multimeter to find out what the problem is.

It certainly sounds like a break in a wire somewhere, which will be near impossible to find it's exact location without some visual clue, such as wires that have become pinched and/or damaged.

If it does turn out to be a break in a wire, then it's probably easier to just run a new one from the wiper stalk to the pump. You won't need to install a separate switch, you can just tap into the existing wiring, therefore bypassing the break in the wire and (hopefully!) bringing it all back to life how it should be.

 

[aryan57]

Normal service has been resumed and my washers are now working again. The problem turned out to be damaged wiring from the switch to the pump motor. So my theory that it was an earth problem was not correct.

Thank you for the help and happy motoring.

 

[Burnerman]

Good work, Mr. A, and sound advice from rs as ever
Where was the wiring fault - did you find it or just bypass? For what its worth, earth points on the wings are usually for the lamp clusters - heavy current draw and so on.
John

 

[aryan57]

Thank you John. The wiring fault was between the switch and the pump. The damage looked like if you had struck the wires with a hammer blow or maybe pinched them. I had +12 volts upstream of the damage and nothing down stream to the pump so it had to be the problem, so I thought. Turns out I was right for once. I cut out the damaged section of the wires and spliced in two new one, then shrink wrapped them

What I was finding so hard to get my head around was earth switching. I had never come across that idea before, I did not even know it was possible. With my car, there are two terminals on the pump , and both should have +12 volts at rest. In operation, one or the other terminal is led to ground, depending on which direction the pump is desired to run. Apparently, earth switching is very common on Japanese cars, of which I have not owned one yet. Now I understand how earth switching works, everything seems so simple.

The washers now really blast the screen, as I discovered that the pump filter was almost completely blocked by blue screen wash crystals.

Thanks again Gaz.

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