Yes. You need to have the circuit completed before it will react properly.

If the car did not come with heated seats in the first place, simply plugging the relay in does absolutely nothing. If your car did not come with the heated seats from the factory, the only way to add it is to do it the way I did by making it a standalone system in the car.

If the car has the harness already you just needed the buttons and relay plug into factory spot

@@LindyBreaksTheStigma no that is incorrect. Most if not all the newer models have the harness but if their SAM unit (ECU) was not configured to have the heated seats then plugging them in simply will not work. I bought the factory parts for the seats, the factory relay, and bought a new factory switch and plugged everything in for “drumroll”… nothing. Simply plugging the parts in when the SAM unit was not configured to have heated seats will do nothing. This is why I show in this video how to add them to ANY Smart 451 by creating a standalone circuit using factory parts for reliability. :)

@@ToyotaGR86Maintenance what’s the difference between the green relay and the black on pn#2000 9857 V001? I want to do the same but that green relay is so expensive!

@@LindyBreaksTheStigma the reason for the green OE relay is it works perfectly. I use it for reliability.

Either buy the individual pins that would work for that connector, or better yet to go on eBay and find a seller who is selling the switches with the connector attached that they simply cut off from a salvage car. If you can’t find that, the next option would be to either individually solder wires to the pins, or go to a junkyard, find the harness itself with the wires, cut it off and buy it.

Thanks mate , another question is , how do you know on the seat connector which is 1&2 (earth & relay wire)

@@ibraarali8544 that I don’t know, but if I were you I would find a wiring diagram and see.

Found the answer - red wire from the seat goes to the relay and the brown is the earth 👍

Keep the videos going , Very insightful

It’s not difficult, it is that the wiring can be reprogrammed using the SAM to have different functionality. In order to not have any issues, it’s actually much easier to add the heated seats as a stand-alone harness. Believe me, I know a car dealership in our family and even that couldn’t convince the Mercedes dealership to reprogram the SAM. Mercedes said if the vehicle didn’t come with heated seats, it would cause too much issues to go that route. Thus, that is my reasoning to add it separately as it’s own harness.

@@ToyotaGR86Maintenance thank you. Love your videos. I’m waiting for the heating pads I order to start this on my ED.

There is a spot for it, but if the vehicle was not originally programmed to have heated seats, those exact same wires that go to the heated seat would be programmed for other functions and use a different relay. I even talk to Mercedes directly, and they explained this to me. Before doing the undertaking of creating a standalone wiring harness for the heated seats, I tried plugging the relay into the factory position, and nothing happens. So yeah, you kind of have to do the custom job if your vehicle never came with heated seats in the first place.

@SmartCarMaintenance so I think mine had them and the last owner sold them and put cloth in for extra money on the side before selling them. I've heard it's under the dash somewhere?

@@John.Winchester on the US models it is under the dash next to the left knee.

@@ToyotaGR86Maintenance on the drivers side or passanger

@@John.Winchester driver side.