Hi there!

I’m going to retrofit the heated seats on my car, or better I already did on the front ones and with new year I’m going to install the resistances in the rear ones.

About the front ones, they initially didn’t work than I realized the first mechanic connected them on J519 (in BCM) but don’t know to which pin without putting the 25A fuse on position 26 of the fuse box; I also discovered (thanks to the second mechanic? he didn’t put any relay (it should be the one with part number 3T0959772B, see the first pic) which controls how much the seats must be warm.

Always the second mechanic, the one who make the blind spot retrofit working, cut out the harness (in a point where he can eventually weld it again easily) and make them work thanks to a temporary relay (it was the end of the day and he want me to test them), as he told me the OEM relay has no connector for the harness coming from BCM, seats and climatronic panel and that goes on the relay of the first pic: this means I now have front heated seats which are just hot or cold, fine for these cold days but not for after them.

So my questions are:

• does anyone know the part number for the small connector (the one one circled on the second pic) and which is it the right harness color/order to connect all the interested parts? Or is it the relay

• When I’ll connect the harness for the rear seats on the J786 with another 25A on position 51 of the fuse box, do I need a second relay with part number 3T0959772B or the first one is enough?

I in fact noticed the relay has (see third pic):

4 big connectors and, in my opinion, they’re 2 positives and 2 negatives to connect harness to BCM/fuse box) which turn on/off the heating

12 small connectors for the heating levels of the seats, and since they (the levels) are 3 they’re exactly for 4 seats, and the central rear one is not heated.

Can anyone help/correct me?

Meanwhile happy 2026

Edited 31 December, 202531 Dec by Benja77

Nothing?