Hyundai i20 no heated rear screen

This vehicle came to us with a problem with the heated rear screen inoperative.

A look at the wiring diagram shows its more complicated than people would think.

When you push the switch it sends signal to chassis ecu, which then sends signal to fuse box and relay, which in turn sends signal to screen and engine ecu (which can raise revs slightly to help with the extra load the screen has).

The circuit tested it was found that the signal was being seen by the chassis ecu but it was not sending signal on. The rest of the circuit was checked in case of further faults, none were found.

A new module was sourced and fitted with confidence.

A first time fix with no parts cannon fired at it.