Rear window defog (& possibly front heated windshield) inop

[philchan1974]

Hi - what's the best process to try and figure out why my defog on 1 or maybe two windows isn't working?

I know I should probably check the fuse first, etc.

But if they check out and the switch lights up ok - where should I check next?

I honestly do not know my way around a multimeter and I know it's a skill I will need to pick up.

Can anyone give me a plain English run down about what to check and if I need to employ a meter how to work it?

Sorry - very basic question, but I'm honestly better with a hammer!

[red90]

First it would help knowing what vehicle this is.

You then need to look at the wiring schematic and follow it through to find the fault.

It might in the end be better to find someone local to help and teaching electrical troubleshooting through a forum is not the easiest.

[philchan1974]

Apologies - yes that would help.

It's an 02 Discovery.

[ANDYD]

A couple of simple things to check,

-Start with the fuse, there is normaly a spare fuse in the fuse cover, so swap it even if the existing one looks ok.

-Inspect the connections where the wires joins the windshield tab. These can get corroded or broken off by large items like furniture or bikes in the back. The front connection some times gets forgotten or broken if a new windshield has been installed / replaced at some time.

-Use the Internet or manual to find out where the relay is located. If it's under the seat it could of been knocked with a vacuum or large foot.

If all of the above items checks out ok then the next steps will likely involve a multi meter....

- Andy

[red90]

I'm not a D2 expert, but a quick perusal of the workshop manual shows that the screen heaters have control through the body control unit computer.

Heated screens
The Heated Front Screen (HFS) is fitted for some market destinations and is operated from a non-latching switch
located on the instrument pack cowl. The BCU will only allow the heated front screen to operate when the engine is
running and controls the time-out period for switching the circuit off.
The heated front screen operation can also be controlled from the Automatic Temperature Control (ATC) ECU on
vehicles fitted with air conditioning.
The heated rear window will only function when the engine is running, and is operated by a non-latching switch on the
instrument pack cowl. The heated rear window can also be operated by the ATC ECU on vehicles fitted with air
conditioning.

As above, check for obvious loose connections. If they are both not working, the problem is most likely more complex.

[philchan1974]

Thanks to you both - i'll try and trouble shoot and report back.