Wagon Wiper Issue

[Mr Polson 10,214]

Having an issue with the rear wiper in my XF wagon.
It will only work with my foot on the brake. That includes the "park" function. The second I take my foot off the brake the wiper stops whatever position it is in.
 
The wiper earth (behind number plate is good).
Everything else brake light related works - cruise control, tail lights, etc.
 
Front wipers work fine all the time.
 
Not really sure where else to look.
 
According to the workshop manual there is a wiper power supply feed to the switch, park control wire to the motor and power to the wiper.
 
I'm far from an electronic genius so simple terms appreciated
 
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[LTD083 278]

Could this be related to the trip computer at all? From memory when you brake the stop lamp lights up on the trip computer?
Worth unplugging it to see if it makes any difference?


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[thorne 1,078]

46 minutes ago, Mr Polson said:

Having an issue with the rear wiper in my XG wagon.

XGs came in wagons? 

[Mr Polson 10,214]

Could this be related to the trip computer at all? From memory when you brake the stop lamp lights up on the trip computer?
Worth unplugging it to see if it makes any difference?


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Wiper doesn't work with trip comp unplugged, probably because the brake lights also don't work with that unplugged.

I wouldn't think the trip comp affects it as the Ghia wagon used to do the same thing with the trip comp and the wiper on that was functioning correctly.

XGs came in wagons? 

Fixed. Stupid phone. Had to add XG to the keyboard dictionary because it kept autocorrecting it to XF when I was commenting on Facebook and changing it to XF. Now it's trying to change XF to XG.

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[gerg 10,871]

Rear wipers are single speed only right? Could the switched wire (ie the one that turns it on) be a switched earth? Would be unusual for a Ford but I'm stumped otherwise.

 

 

Actually nah forget that, it makes no sense

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[Mr Polson 10,214]

Fixed it - sort of.

Looked at the wiring diagram, power is supplied to the switch, then the switch just sends that power to the motor. Park control always has power.
Therefore there must be no power to switch (unless brakes are on).

Cut power supply wire and wired it to the wiper fuse. Wiper now works as normal.

Am I correct in assuming there must be a crossed wire between the wiper power supply and brake light power wire?

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[deankxf 20,266]

those tailgate wires are known to get broken over time, but i can't think of how this problem came about unless you plugged it in wrong when doing the dash? 

if its fine now, outcome successful..

[Panko 2,480]

Haha i suspect someone has wired that up for some stupid reason to take power from your brake lights. 

 

You raised another issue though. Why are your brake lights not working when you unplug the trip computer? 

That makes no sense. 

The only interaction with the trrip computer the brakes lights have, is a warning light when they stop working, or you blow a globe. 

You have to remember, that the fundamentals of the wiring is the same as a GL, which didnt have all the fancy stuff like the trip computer. 

[Mr Polson 10,214]

Haha i suspect someone has wired that up for some stupid reason to take power from your brake lights. 
 
You raised another issue though. Why are your brake lights not working when you unplug the trip computer? 
That makes no sense. 
The only interaction with the trrip computer the brakes lights have, is a warning light when they stop working, or you blow a globe. 
You have to remember, that the fundamentals of the wiring is the same as a GL, which didnt have all the fancy stuff like the trip computer. 

They've never worked without the trip computer (or basic clock) in both my original Ghia wagon, the ute when it had a Ghia dash, and this.

The dashboard wiring is rather different between Ghia and GL, my understanding is with the brake light circuit, the power from the light switch runs to the trip computer, and then to the brake lights. If the trip computer is unplugged, then the brake light power circuit is incomplete.

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[Panko 2,480]

Really? 

Ill have to look into that. Im sure mine worked without it, but maybe not.