Dodgy Demister
- Thread starter andys
- Start date
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- heated rear window
Oh well
Thanks
Has the switch been replaced yet? Maybe it just isn't latching on and/or not sending a long enough signal. ( Starting with the simplest item first - I haven't a clue as to what signal is sent by the switch or looked for by the BCM. Heaters I can cope with but all this BCM wizardry is alien to me
anything is worth a try,
The VCDS HRS output test failed too (Inactive)
Throw in the towel time. The option of swapping the switches to check was a non starter as they're integrated into the heater control panel, but I've had the stereo and centre trim panels off to check for any dodgy connection to it, or signs of wire damage, kinking or pinching - nothing.
Then started on the fusebox again, this time removing any add-on wiring, piggybacks etc that I've added (though looking back through my forum posts it turns out they were all done after the discovery that the HRS wasn't working...) Then ensured that the fuse layout matched exactly to a photo I took of it 2yrs ago before any mods, then checked that the fuse values and positions matched the fuse card, before yet again checking that each and every fuse had power to both sides - nothing
Removed the driver's side lower trim panels so that I could drop the BCM and again check for any visible wiring damage or loose connectors. Also unplugged the BCM itself and gave the contacts a clean before putting the plugs back in the sockets and making sure they were properly clipped in. Again I could probably have missed this step as the BCM has been out and plugged back in again by an alarm fitter when he was wiring it in, long after the HRS stopped working - nothing
Finally plugged VCDS in again and repeated the output tests and the check to see that the BCM noticed when the window element was unplugged. Results exactly as before.
So logically it can't be the switch/control panel, as that is detected. Can't be the heating element or the wiring to it as the resistance seems correct and the BCM is detecting continuity or not. Can't be the coding as all options have been tried. So the only things left that I can think of are the BCM itself (but absolutely everything else works fine), or wiring damage/poor connections between where I can see it disappearing below the stereo to where I can see it coming out below the steering wheel.
I've spent upwards of 20hrs investigating this and massive thanks to @Dellmassive and @mmi for all the help but I'm just going to live without a HRS for now and tell the dealer to have a look when it goes in for its next service this autumn.
Then started on the fusebox again, this time removing any add-on wiring, piggybacks etc that I've added (though looking back through my forum posts it turns out they were all done after the discovery that the HRS wasn't working...) Then ensured that the fuse layout matched exactly to a photo I took of it 2yrs ago before any mods, then checked that the fuse values and positions matched the fuse card, before yet again checking that each and every fuse had power to both sides - nothing
Removed the driver's side lower trim panels so that I could drop the BCM and again check for any visible wiring damage or loose connectors. Also unplugged the BCM itself and gave the contacts a clean before putting the plugs back in the sockets and making sure they were properly clipped in. Again I could probably have missed this step as the BCM has been out and plugged back in again by an alarm fitter when he was wiring it in, long after the HRS stopped working - nothing
Finally plugged VCDS in again and repeated the output tests and the check to see that the BCM noticed when the window element was unplugged. Results exactly as before.
So logically it can't be the switch/control panel, as that is detected. Can't be the heating element or the wiring to it as the resistance seems correct and the BCM is detecting continuity or not. Can't be the coding as all options have been tried. So the only things left that I can think of are the BCM itself (but absolutely everything else works fine), or wiring damage/poor connections between where I can see it disappearing below the stereo to where I can see it coming out below the steering wheel.
I've spent upwards of 20hrs investigating this and massive thanks to @Dellmassive and @mmi for all the help but I'm just going to live without a HRS for now and tell the dealer to have a look when it goes in for its next service this autumn.
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I've got some spare hair if you have torn all yours out in despair!
Defo keep us posted with what the dealer says.... rattled my brain this one. =]
Next time you have a VCDS session - What have you got in 09-Cent. Elect --> Advanced ID? Any flash attempts? Mine are all “0”.
I've just read this thread after MMI posted a link to it. I've added a tailgate to my van and therefore having to run wires for the wiper, screen and lock.
I changed my heater controls for a £10 parts from eBay which is off a Golf. It was a straight swap and as soon as I swapped it, I was able to switch on the HRS when the engine was running. The light would illuminate for a few seconds and then go out.
I changed the coding by just ticking the boxes in Address09 and ran a wire to the rear lid connector from the BCM. I'm also getting 5.7v on this wire when the screen is off, and 12v when active.
The wire goes direct from the BCM to the screen without any relays but there are a few joins. I would give it one more go running a tempory wire direct from the BCM to the screen, missing out all the connectors along the way.
Maybe I was lucky mine worked first time, but I'm unluck in not being able to get my lock to work yet, which I also think is a wiring problem, not coding.
I changed my heater controls for a £10 parts from eBay which is off a Golf. It was a straight swap and as soon as I swapped it, I was able to switch on the HRS when the engine was running. The light would illuminate for a few seconds and then go out.
I changed the coding by just ticking the boxes in Address09 and ran a wire to the rear lid connector from the BCM. I'm also getting 5.7v on this wire when the screen is off, and 12v when active.
The wire goes direct from the BCM to the screen without any relays but there are a few joins. I would give it one more go running a tempory wire direct from the BCM to the screen, missing out all the connectors along the way.
Maybe I was lucky mine worked first time, but I'm unluck in not being able to get my lock to work yet, which I also think is a wiring problem, not coding.
Mine was a factory fit tailgate and demister though, and the bcm can see it when testing. I've given up on it to be honest, too many other things on the list above it.
That’s good news @Littleblackflash - I’ve got a Passat part indoors with the HRS and heated seats options, so I hope this too works for me.
Sorry to hear you haven’t solved it, @andys
