red66toy
Supporting Vendor
Hello everyone!
So after reading way too many BMW forum posts, I figured out how to use the factory installed seat heat mats.
I have not fully completed this install, however I have tested the wiring setup listed below and my seats heated up very nicely.
Supplies I used:
-2000 328ci BMW seats with factory heat and the body side plugs (plus a short length of wire).
-Two rear seat heater switches from a BMW e38/e39. These are cheap in ebay. I chose these switches because I liked the idea of BMW seat heater switches controlling BMW heated seats. Also these switches are small and have a nice heat adjustability wheel on them. I made sure to get the rear plug with a short length of wire that connects to the back of the switch. The seller on ebay gladly included it for free with the switch.
-30amp power source and 12ga wire to run from the source to both heat switches. The BMW wiring diagrams show a 15amp fused power source for both seats but I had just installed one of the awesome relay accessory blocks that @slcfj62 makes and it had a spare 30amp relay slot open.
-14ga and 18ga wire to run from the switches to the seats
- Because I didn't have the wires and terminals in the body side plug I ordered:
Two 61130005197 wire terminals. Purchased from ECS tuning
Four 61138364834KT wire terminals. Purchased from ECS tuning
First, after I got the seats I had to check if they were indeed factory heated seats, to figure this out I looked under the seats and looked for the terminals in locations 23, 24, and 25:
Pin 23 under the seat is the negative thermal coefficient (NTC) signal terminal (I'll explain in a sec)
Pin 24 is ground
Pin 25 is hot
So once I established that the seats were factory wired for heat, next I turned my attention to the yellow body side plug that connects to the yellow socket under the seat:
Unfortunately, my plug did not have seat heater electrical terminals already installed in the three slots (23, 24, 25) indicated by the white arrow in the previous photo.
To install these terminals, I first removed the black cover indicated by the yellow arrow in the previous picture.
Next I securely installed the 61130005197 terminal and attached wire pictured below (with enough length wire to reach the switch location in the center console) and slid it into the 23 slot in the yellow plug. This is the NTC connection that will tell the heater switch when the seat is hot enough so it doesn't get too hot.
Next I securely installed 14ga wire into the 61138364834KT terminals pictured below(with enough length to reach the switch location in the center console) and slid each connector into the 24 (ground) and 25 (hot) slots in the yellow plug.
Once I had all three terminal slots filled on each of the yellow plugs I slid the protective black cover back onto the plug. I did this for both seats.
Once the plugs were wired up, I turned my attention to the switches. This is what they look like and here is the wire labeling:
As for switch mounting this is where I plan to mount my switches (they are not pressed in all the way in the photos). They do fit nicely and flush in the slots. Might need a tiny trim/shim around the edges.
So here is how I wired the switches to the seats:
I ran the hot fused wire to the pin-3 wire on both the switches, they share the same power source wire according to BMW schematics. Then for each switch separately: from switch Pin-5 and 6 I routed the wire to Pin-25 wire under the respective seat for that switch. The Pin-23 wire under the seat was connected to pin-2 wire on the switch to supply the negative thermal coefficient (NTC) signal. Pin-1 on the switch connects to a night illumination 12v source. Finally I connected the pin-24 ground wire and the switch pin-4 wire to a good ground source.
The switches have a built in voltage monitor and the seats don't really heat unless the truck is running so the battery doesn't run down. Pretty cool feature. Very happy with this setup!!
I am happy I can finally contribute something worthwhile to this great forum of cruiser knowledge.
UPDATE 1/4/2021:
I am finalizing the install of these switches and to confirm how they work I hooked them up to a power supply. I tested two styles of E46/E39 heat switches and both work the same way. Heat is regulated by pulsing the power. High heat setting results in longer power cycles and low power setting results in short cycles of power (you can see this in the video). Based on this. You can wire these switches to trigger a relay to supply power to the seats, or have power run through them like BMW did. It looks like one seat draws about 7.5-8amps of power so fuse accordingly.
So after reading way too many BMW forum posts, I figured out how to use the factory installed seat heat mats.
I have not fully completed this install, however I have tested the wiring setup listed below and my seats heated up very nicely.
Supplies I used:
-2000 328ci BMW seats with factory heat and the body side plugs (plus a short length of wire).
-Two rear seat heater switches from a BMW e38/e39. These are cheap in ebay. I chose these switches because I liked the idea of BMW seat heater switches controlling BMW heated seats. Also these switches are small and have a nice heat adjustability wheel on them. I made sure to get the rear plug with a short length of wire that connects to the back of the switch. The seller on ebay gladly included it for free with the switch.
-30amp power source and 12ga wire to run from the source to both heat switches. The BMW wiring diagrams show a 15amp fused power source for both seats but I had just installed one of the awesome relay accessory blocks that @slcfj62 makes and it had a spare 30amp relay slot open.
-14ga and 18ga wire to run from the switches to the seats
- Because I didn't have the wires and terminals in the body side plug I ordered:
Two 61130005197 wire terminals. Purchased from ECS tuning
Four 61138364834KT wire terminals. Purchased from ECS tuning
First, after I got the seats I had to check if they were indeed factory heated seats, to figure this out I looked under the seats and looked for the terminals in locations 23, 24, and 25:
Pin 23 under the seat is the negative thermal coefficient (NTC) signal terminal (I'll explain in a sec)
Pin 24 is ground
Pin 25 is hot
So once I established that the seats were factory wired for heat, next I turned my attention to the yellow body side plug that connects to the yellow socket under the seat:
Unfortunately, my plug did not have seat heater electrical terminals already installed in the three slots (23, 24, 25) indicated by the white arrow in the previous photo.
To install these terminals, I first removed the black cover indicated by the yellow arrow in the previous picture.
Next I securely installed the 61130005197 terminal and attached wire pictured below (with enough length wire to reach the switch location in the center console) and slid it into the 23 slot in the yellow plug. This is the NTC connection that will tell the heater switch when the seat is hot enough so it doesn't get too hot.
Next I securely installed 14ga wire into the 61138364834KT terminals pictured below(with enough length to reach the switch location in the center console) and slid each connector into the 24 (ground) and 25 (hot) slots in the yellow plug.
Once I had all three terminal slots filled on each of the yellow plugs I slid the protective black cover back onto the plug. I did this for both seats.
Once the plugs were wired up, I turned my attention to the switches. This is what they look like and here is the wire labeling:
As for switch mounting this is where I plan to mount my switches (they are not pressed in all the way in the photos). They do fit nicely and flush in the slots. Might need a tiny trim/shim around the edges.
So here is how I wired the switches to the seats:
I ran the hot fused wire to the pin-3 wire on both the switches, they share the same power source wire according to BMW schematics. Then for each switch separately: from switch Pin-5 and 6 I routed the wire to Pin-25 wire under the respective seat for that switch. The Pin-23 wire under the seat was connected to pin-2 wire on the switch to supply the negative thermal coefficient (NTC) signal. Pin-1 on the switch connects to a night illumination 12v source. Finally I connected the pin-24 ground wire and the switch pin-4 wire to a good ground source.
The switches have a built in voltage monitor and the seats don't really heat unless the truck is running so the battery doesn't run down. Pretty cool feature. Very happy with this setup!!
I am happy I can finally contribute something worthwhile to this great forum of cruiser knowledge.
UPDATE 1/4/2021:
I am finalizing the install of these switches and to confirm how they work I hooked them up to a power supply. I tested two styles of E46/E39 heat switches and both work the same way. Heat is regulated by pulsing the power. High heat setting results in longer power cycles and low power setting results in short cycles of power (you can see this in the video). Based on this. You can wire these switches to trigger a relay to supply power to the seats, or have power run through them like BMW did. It looks like one seat draws about 7.5-8amps of power so fuse accordingly.
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