No heating at all, failure mode is normally that the tiny wires start failing giving foggy stripes. However there is no heating at all in my case. The fuse to the control relays is ok. The two fuses afyer the relays are ok. The relays are in place, no visible damage. Whrn I press the button on the console it does light up. But no heating. So I believe the fault is in the common part before the relays. Is there a known issue?

Is there a wiring diagram to download from somewhere?

 

I found the wiring diagrams and the ac control unit controls the relays directly. So I will have to check voltages at the relays and take it from there. I suspect either wiring to the relays (the common line) or the switch in the control panel itself.

 

I found the plugs just in front of the screen that connect to the screen. The voltage from the relay is 12V as it should be. The resistance of the heater elelements is near infinite so basically open circuit.

Is it really common that these burn out completely? On other cars with the heated screen they fail gradually.

I don't know if the screen has ever been replaced. Where does the wire ahead of the screen connect to the screen itself? I want to check the connection is actually there.

 

It sounds like you answered your own questions. If you have power coming out of the relay without being disconnected, you can rule that out. If you ohm’d out the screen element and it’s reading infinity, then it’s an open circuit. Get the windshield replaced. The only thing you need to check is the ground side.

 

My car had only one wire working on driver side and three on passenger side. So they can be burned out completely. Heated windscreen is quite common feature in EU Fords. Most of them has at least many wires broken. Simple fault, easily expensive fix.