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  #11  
Old 22nd December 2016, 12:20 AM
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47p2 47p2 is offline
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The rear heater elements that are prone to breaking are there to heat the rear compartment when the front is set colder than the rear. Therefore if the front is set at 22 the rear should heat to 22 or above. However if the front is set to 18 and the rear passenger wishes 22 but the heater element is broken then the rear will only heat to 18
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  #12  
Old 5th November 2019, 07:26 PM
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I thought I would have a look at my heaters as they are both dead. They are easy to remove - it takes 60 seconds.

I was hoping to replace the element as you can buy various 12v heating elements from china.

1. slide the front seat all the way forward.
2. Pop off the two round plastic nut covers.
3. Remove the two 10mm nuts.
4. Lift the flap of carpet at the front and back and you will see how it needs lifting at the back over the studs and it is inserted into a duct at the front.
5. Undo the electrical connector at the side/front. Typical VAG type type. Push it in hard, press the tab hard with your thumb until it clicks in and then pull the plug out. If it doesn't come out, repeat but lever it out to unplug it while still squeezing the tab.
6. Lift at the rear and withdraw.

Well, inside the house, I split the two casing halves which are held together along it's seam by 6 metal spring clips.

What a terrible design. It works by overheating several transistors with heatsinks attached! There is what is possibly a blue bead thermistor to give temperature feedback, and maybe a thermal fuse. It is all potted in black epoxy which make it's hard to reverse engineer, if not impossible.
What a joke. It is worth about 5 each but Audi charge 200 each and they don't last at all.

I am thinking of breaking it all out and seeing if I can remake the original design with new components.

While I was taking them out, I sadly found both to be wet and the foam insulation under both seats sopping wet. I have the pleasure of looking into that now. I have no sunroof, so hoping it's the A/C drains.

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Looking at the wiring diagram, we have:
PINOUTS
1 Switched 12V
2 LINBUS signal
3 LINBUS ground
4 Ground

As it has LINBUS connections, there is no way to turn on/off/regulate without retaining the circuit that is hidden in a trough of epoxy.



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Last edited by snapdragon; 5th November 2019 at 08:07 PM.
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  #13  
Old 5th November 2019, 08:03 PM
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Quote:
Originally Posted by snapdragon View Post
It works by overheating several transistors with heatsinks attached!
I'm not versed in electronics but that was exactly my thought when I dismantled mine to see if they could be repaired. Ended up just binning them.
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My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts

Sold! 2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights

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