Sort of new to this and looking for a bit of advise.
I've purchased mk4(08 plate) caddy seats for my mk3(05plate) caddy, no probs fitting, only problem is that some of the multi plugs underneath are different from my original seats, so I can't get the heated seats to work. Strangely the mk3 seats have a resistor relay underneath the seat(part no: pa6-gf5) where as the mk4 seats don't?. . Is the relay situated else where in the mk4?.
Any/all suggestions welcome?
Hi, welcome to the forum.
You will more than likely need some wiring adaptors to get your seats to plug in.
There weren't many 05 plate Caddys with heated seats from the factory so maybe you have some aftermarket equipment in there?
You say your new seats are from a mk4 (08 plate), did you mean to say 18 plate Caddy4?
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You more likely have one module under each seat as this is the early module setup from VW. Newer seats more likely have the module under the passenger seat only as I believe the change came in early 2008 from 2 modules into 1 for both seats.
Your current seats having modules under each seat will have two power feeds (live and ignition switched) ground, cecm wire and heater panel wire.
Post some pics of the setup to clarify if it’s oem setup you have or aftermarket
Pic 3 top tight loose 8pin plug that’s where the newer module should be but seems it was removed.
Yellow are airbags, small 2 pin seatbelt warning and small blue 2pin seat occupancy sensor.
You can make adapters to get them working but that would require running couple extra wires from under passenger seat and also you need to get the module.
Cheers Stan the man. That's very helpful.
I've contacted the seller to see if or why he might have removed it. Couple question
1) Any ideas where I might be able to get the module?
2) How would I get adapter plugs made, I was thinking of finding the correct wires and just soldering together?
Another option could be perhaps swapping the looms under the seats over?
I might be mistaken but the backrest and seat frame elements on both seats new and old could be same?
Worth checking perhaps before you start cutting/soldering.
Ignore the wiring for seatbelt buckle on drivers and passenger and occupancy sensor on passenger seat.
stan-the-man wrote:Pic 3 top tight loose 8pin plug that’s where the newer module should be but seems it was removed.
Yellow are airbags, small 2 pin seatbelt warning and small blue 2pin seat occupancy sensor.
You can make adapters to get them working but that would require running couple extra wires from under passenger seat and also you need to get the module.
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I don't suppose I could buy one of those modules of you stan the man
What exactly does the module Do? Could i not just by pass it?. I suspect it stops the seats from overheating by turning the power to the heated seat element off after a time...?
. Is the relay situated else where in the mk4?. 
