Member Since: 11 Oct 2009
Location: Bledlow
Posts: 901
How to: Wiring heated D4 seats in a D3
OK, so I have been struggling to get the heating elements in the manual adjustment D4 seats I fitted to my D3 working for some time but as is so often the case, someone has agreed to buy the car and I need to get it working before it goes. Tonight I achieved hot seats!!
In summary, you need to bypass the heated seat module (marked Volvo) under the D4 seat that the heating pads plug into and wire them directly to the D3 loom (before the big plug).
Release the big plug from the bottom of the seat (the one with the 8mm nut holing it together) to get better access; slip a small flat headed screwdriver between the steel tongue on the seat frame and plastic clip and pull forwards.
Take off the lid of the plug (on the nut side) by releasing the side clips.
On the back of the big plug, on the car side, find the plug with 4 wires disappearing into it (a thin bright green, a thin black and dark green, a thick black wire and a thick blue/pink wire). The thin green and black/green wires are the thermistor circuit and the black (-ve) and pink/blue (+ve) wires are the seat pads' power. I cut these four wires away from the back of the plug as close as a I could and then released some slack from the loom so I had something to work with.
On the D3 the seat heat pads are wired in directly to the seat loom through the big plug with the nut, whereas on the D4 there is a module that sits between the plug with the nut and the seat pads. You need to remove and bin the TRW/Volvo module and the loom that sits between the big plug and the module.
Click image to enlarge
Depending on how your D4 seats are supplied: remove the short loom with a Heated Seat Module sticker on it which is connects the heated seat module with the large distributor plug (with the nut). Remove this small loom and bin it (three wires, black, red and thin brown).
Find the heated seat module on the bottom of the seat with three plugs. (It’s marked Volvo and TRW). Having binned the loom with the black, brown and red wires that connected to the large plug above, you are left with two plugs; one with 4 wires - two yellow/white wires (the thermistor connectors) and two grey wires (one heater circuit) and another plug with two black wires (the second heater circuit).
To make the thermistor circuit connect one of the yellow/white wires to one of the thin black wires and the other yellow/white wire to the black/green wire (I used Wago connectors because I have them lying around).
To get the heater pads to work you need to create a series circuit with the black and blue/pink wires from the large plug through the two heater circuits. i.e. Black wire (from large plug) to grey wire from heater circuit 1 , then second grey wire from heater circuit 1 to black from heater circuit 2 then second black from heater circuit 2 to purple/pink wire. (sorry, it's not a great photo...)
Then tidy up and repeat for the other side and you should have toasty D4 seats in your D3…
Apologies for no photos, I’ll try and take some tomorrow…-------------------------------------------------------------------
D4 '15 (64) Se Tech Indus Silver
Tesla Model Y LR (22)
Audi TT Roadster 225 (52)
Tesla Model 3 LR (70) (gone)
Porsche Boxster '96 2.5 5spd project (P)
Mini R52 S (54)
BMW 330e eDrive MSport '16 (gone)
D3 '07 (56) XS TDV6 Buckingham Blue (gone)
Last edited by hgrimmett on 22nd Sep 2017 8:16 am. Edited 6 times in total
20th Sep 2017 9:15 pm
LR3norway
Member Since: 25 Dec 2016
Location: NORWAY
Posts: 193
Pictures would be great
21st Sep 2017 8:03 am
hgrimmett
Member Since: 11 Oct 2009
Location: Bledlow
Posts: 901
Some photos added - sorry they were a bit of an after thought... -------------------------------------------------------------------
D4 '15 (64) Se Tech Indus Silver
Tesla Model Y LR (22)
Audi TT Roadster 225 (52)
Tesla Model 3 LR (70) (gone)
Porsche Boxster '96 2.5 5spd project (P)
Mini R52 S (54)
BMW 330e eDrive MSport '16 (gone)
D3 '07 (56) XS TDV6 Buckingham Blue (gone)
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