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Fiesta Mk IV contact plate

The tailgate contact plate on my Mk IV Fiesta looks like it became HOT at some time in the past and the plate carrying the heated rear screen power has sunk into the plastic surrounding the contact plate and is no longer making contact with the contact pin in the tailgate. The LED in the heated rear screen push button is on permanently whenever the ignition is on and there is 12V on the heated rear screen plate of the contact plate.

Holding the heated rear screen button in turns off power at the contact plate but release the button and power returns at the plate.

Is the heated rear screen button meant to be momentary action or locking? I took the push button apart but cant see any bent or broken parts inside.

Maybe the push button is meant to be momentary action as the heated screen is meant to turn off automatically after a period of time.

Has a relay became stuck closed somewhere or is there another explanation?

Thanks

Reply to
Alt Beer
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perhaps the screen connection has melted into an adjacent powered connection (the one for the wiper parking has power whenever the ignition is on)

Reply to
Mrcheerful

Thanks - good thought but...

Its not shorting at the contact plate. I used a soldering iron to completely dig out and remove the heated screen contact plate and wiring from the melted plastic. Also when I hold the heated screen push button in 12V is not present at the plate??

Reply to
Alt Beer

The switch just powers the relay, which feeds back to the switch and to the screen. what happens if you pull the fuse for the screen or pull the relay?

Reply to
Mrcheerful

There is hardly any slack in the loom to the fuse / relay box. I'll try to access the relay area again tomorrow when I have more time. Looking at the circuit diagram the heated rear screen switch in the car is for use with the 'No Time Delay' relay. In which case it should be a latching type switch instead of the momentary type fitted. It will be interesting to see whether the relay fitted is a 'Time Delay' type or not.

The internal light is dims slowly when leaving the car so there is at least one time delay relay fitted. The car is a Zetec S so may have a time delay heated rear screen relay.

May be someone has changed the switch or relay in the past and there is a mismatch between switch and relay.

Thanks

Reply to
Alt Beer

The problem was caused by the push switch not latching in the OFF position, it was permanently on. Bent a small metal tab in the switch and sprayed with switch cleaner. Now you get a nice reliable latching On and Off.

Thanks

Reply to
Alt Beer

well found, I'll try to file that in my memory, just in case.

Reply to
Mrcheerful

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