rear demister

[swys]

Hi there recently got a saxo 1.1 desire 2001 everything is good other than the rear demister doesn't seem to be working I push the button and it doesn't light up. I have read about doing the ignition mod but thats apparently if PAS, heater blowers and rear demister don't work only my rear demister isn't working. I haven't checked fuses as I don't know which one it is and gather could be a relay.

Anyone help me out please.
Thanks.

[stevo67]

Check the fuses 1st if they`re ok then change the demister switch mate.

[Rallynavigator]

1-Can you hear the relay as you press the button
2-Check the fuse for the screen
3-Check the power supply to the switch and relay. It could just be the switch light not to say the switch is faulty. Make sure you have a good earth on the relay and switch
4-Check the voltage at the rear screen. You should have 12v at one end and the voltage will degrease as you move further along the screen

[swys]

thanks to both of you will give it a shot.

[swys]

Well had a look today. Its not the fuse thats ok, when I press the button I don't hear any relay. Also to note I had my lights on earlier and the heater button was dim so I pressed it and it was brighter but the switch doesn't stay lit goes dim again its as if the switch is broke.

I am not sure how I go about checking for voltages etc... I do have a multimeter but am not really an electronics person. How do I check power supply to switch and relay? and check voltage at rear screen?

Thanks.

[swys]

Well went to a scrap yard today and tried both another relay and switch and still same issue you press the heater button and it lights but won't stay lit. You can hear the relay clicking when pressing button. Had a good look at rear window the connections all look clean and can't see any breaks in heater element?

At a loss?

[swys]

Really bugging me this want to figure it out. I had the rear interior boot trim of to have a look and noticed on one corner the trim had been tight up against the rear heater wire and looks like its caused abit but doesn't look severe, could this be cause?

http://i1263.photobucket.com/albums/ii632/swys33/IMG_20131023_180201.jpg

[Rallynavigator]

Put a multimeter on that connector, the other end on the opposite side, what voltage have you got??

[Rallynavigator]

Does it make any difference if that wire is manipulated ?

[swys]

Rallynav I have disconnected both the terminals at back of heater element put my probes in each one with multimeter connected started car switched multimeter to dc voltage and got no reading at all 0v I pushed the heater button and still 0v?

does it mean there is a break somewhere in wiring?

[Rallynavigator]

Go to the positive terminal . So go on the terminal and put your meter on the terminal and then earth with the other , what voltage do have have as opposed to going across the screen. Is the damaged wire in the picture the positive. If it go to the side if the wire prior to damage and check again.

Look at the relay power supply. You said you can hear the relay from memory is this right. Do not presume if you can hear the relay it is working . Check at terminal 30 for a voltage similar to that of battery voltage ??

[swys]

Well after all this it was a bloody fuse! I didn't realise 2 fuses controlled the rear heated screen, I was just looking at F2 its only until other day I come to use the horn and it didn't work thought must be fuse looked at fuse diagram on here and its F5 which also controls heated rear screen, well mine was blown! lol replaced and everything is working now. :)

[Rallynavigator]

Excellent result for you , cheap fix