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Stang
19-07-2015, 02:00 PM
Hello All!

I am baffled as to why my rear window demister doesn't operate. The light comes on, on the dashboard button, but it doesn't throw the relay under the bonnet. I've tried switching over the relay but the relay doesn't seem to be the issue. If I manually throw the relay, the demister works!

Has anyone else experienced this fault, and obvious question: what's the fix?!

Looking forward to a resolution!
Rupert

scooter
19-07-2015, 02:22 PM
Check the switch output side

Stang
20-07-2015, 08:01 AM
Thanks Scooter - I assume I would need to remove the switch from the dash to check the output side? Does it just 'snap' out with a screwdriver? I dont want to remove the dashboard!

greeners
20-07-2015, 02:35 PM
HRW switch is part of the HVAC ECU and not a seperate item. If you remove the cover panel, there are four screws to remove it

https://www.two-sixties.co.uk/mgoc260/html/f0rum/attachment.php?attachmentid=7640&stc=1

I would try unplugging both connectors and plugging them back in see if that cures it.

Failing that try a battery reset

peterv8
20-07-2015, 02:54 PM
Check the connectors at the rear window and measure if there is 12 volt when demister on.

Stang
21-07-2015, 08:16 AM
Thanks for the tips, everyone - good to see this forum is alive and well!

I've tried the battery reset, and it's not the connectors at the rear window. That leaves checking the connectors at the back of the ECU :(

peterv8
21-07-2015, 01:36 PM
Thanks for the tips, everyone - good to see this forum is alive and well!

I've tried the battery reset, and it's not the connectors at the rear window. That leaves checking the connectors at the back of the ECU :(

Is there not a fellow member near you who can lend out his HVAC ECU or try yours in his car? I'll be glad to do it but I'm a bit far from you!:-)

Stang
22-07-2015, 09:15 AM
Hi Peter - Actually, you are further than you think; I'm in Dubai! The car is in Bath, UK, and I'm making plans to get it back on the road. There used to be another ZT260 owner in Bath, but it was another lifetime ago!