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Discussion Starter #1
My rear defroster will not _stay_ on when I push the button. It has been like this since I got the car a few months ago. Can anyone tell me if the rear defroster stays on due to some electrical/timer setup or should the button on the wiper stalk just click down (like the rear fog light switch)?

That'll give me some where to start looking. If it's a simple switch in the stalk than I'll need a new one probably. But if it's controlled electrically I can start looking for wiring diagrams and thew rest to figure it out.

thanks,

Mikel
1997 155 2.0 16v
 
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Discussion Starter #2
Hi Mikel,

the rear defrost switch does not stay down. When you push the button, the heater comes on for a set time, but can be switched off by pressing the button again.
That's how it is on my 97 2.0ts

good luck,
hans
 
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Discussion Starter #3
Thanks Hans,
Now I know it's an electrical fault that I can start to chase down,

Mikel
 

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There's a timer relay, but I think it's an expensive part from Alfa. I don't know if you can find something compatible from an electronics supplier though.
 
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Discussion Starter #5
I pulled the yellow relay below the double relay on the fuse box (my mechanic told my that was it). It's an ordinary relay but it seems to be fine (tested by swapping it with another with the same number/rating). No joy.

The stalk switch will turn on the defroster and you need to hold down the button to keep it on.

Anyone know where I can get a wiring diagram for this circuit?

thanks again guys,

mikel
1997 2.0 16v
 
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Discussion Starter #6
keep an eye out for daiblack, he seems to be the resident expert on wiring diagrams etc.
 

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OK heres the diagram

If this doesn't work click on the LINK

Relay 135 is the 3rd from bottom on the RIGHT bank of relays on fuseboard. :D
Relay 12 is the bottom one on the LEFT bank of relays on fuseboard. :D
Fuses are the 7th and 8th from top on the LEFT column of fuses. :D
 
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Discussion Starter #8
I had a similar problem. It was the earth connection shared with the aerial (at least it is on my 1.8ts)
Also occasionally, if I've got a lot of electrics on (headlights, radio, blower etc.) the heated rear window won't work.
 
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Discussion Starter #9
Thanks, the diagram is a big help. Looks like it's either a problem with relay 135 or the ground as suggested, as the rear heater will work if the button is held down. I couldn't get replacement relays today at the local parts shop.

I can't quite make everything out on the diagram as it's saved as a jpeg. I could get a job with the CIA after trying to interpret some of the dark smudges. Any chance I could push my luck and ask for a bitmap or other higher res format? I've got a sneaking suspicion theres a mobile WMD plans beside relay 12 ...

mikel
 

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Be interesting to know your findings as mine has been doing this :rolleyes:

Hopefully it`s just a relay :D
 
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Discussion Starter #12
Update:
Thanks Diablack, I can read it much better now.

I tested the two relays (12 and 135) and the two fuses. All seem fine.

Both relays are identical yellow 12v 30A 5pin relays labelled A727. Maybe someone with a working defroster can confirm as I've two previous owners who might have changed them before me.

Mikel
 
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Discussion Starter #13
had this prob on my 2.0 8v, relay which controlled demister timer kept workin loose. solved it in the end by takin it out bendin the pins for a tighter fit an.... Hey presto! on mine its at the bottom left of pull down panel.
 
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