Rear heated seats
 

Hey guys. Recently picked up a 04 4.8iS and drive it back from NY to TX.
The rear heated seat worked, or at least the light came on when pressed. But when I got home, while cleaning it out. Press the rear seat heater buttons and nothing.
I've popped off the seat bottom. Vacuumed out the years of debris and checked the wires. Al looks good. I removed the back of center console and checked the buttons. Why're still locked into the harness and nothing.
I've checked the fuse. They're good. No heat on the back seat.
No errors in INPA.
What else can I check? Any clues, ideas?

Thanks.



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Just a WAG but maybe there is a pressure switch that activates the heater element when it senses a person sitting in the seat. Try it while sitting in the seat for 5 minutes and see if you get heat.

Woah. Is that it? No way. I'll have to try that. I hope thats it. I'll feel stupid, but I'd be happy.


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My 2003 rear heated seats were inop also.
I lifted up the rear bench to find that the harness was
not installed. Perhaps your wiring isn’t clipped tightly.

When I lifted the seat to clean it. All the harness looked fine. Everything plugged in and nothing seemed out of place or damaged.


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Just checked. Unfortunately this didn't make a difference. :(


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I had rear heated seats in my 04 as well, there is no pressure sensor that activates the heating element as Calipsoe suggests

Have you ohmed the seat heating element to verify that there is no break in the heating element?

No, I have not. Can I check the element without having to remove the covers?


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Just disconnect the seating element at the connector and use an ohm meter to check for continuity.

Ah, ok. Will try this later this week.


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^Definitely do a continuity test.

But in the interest of covering all bases... you checked the fuse?

I did. Was the 1st thing I checked.
Will check the Bentley manual and see it suggests any other fuses besides what the glovebox said.


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Rear heated seats
 

Ok. I finally got around to checking continuity.
1 plug, 2 wires coming off going to left and right side.

Left to right.
1 brown from each wire on 1 pt
1 Blue yellow
1 brn white
1 ylw white
1 brn ylw.

1 multimeter probe into the brown as grnd.
Grnd + blu/ylw - 10ohms
Grnd + brn/wht- nada
Grnd + ylw/wht- 10ohms
Grnd + brn/ylw - nada.

Are all of them supposed to be closed?
And if 2 are not open how come it doesn't partially work?

Checking them where they plug into the car produces similar results to match the seat harness



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Any ideas what this means?


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Where can I get one of the relays for the rear seat heater. Figure I can try that before I resign to it being the seat element.


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Those numbers make sense, you have 10 ohms on each heating element. The other 2 wires are the temp sensors.

So where do I look now. If that checks out where else do I look?


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Check for voltage at the element wires. I imagine rear buttons are like the front and a light comes on when you press the button? If there is no light then maybe start checking in that direction. looks like power for rear seat heaters comes from unloader relay so maybe check that.

So do the same check, but for voltage this time?
I already checked the switches/buttons and plugs. All seemed well and nothing looked out of place. No damaged wires, nothing.


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According to the wiring diagram (you have Benltey manual right?) the rear seat heaters get power from the unloader relay. Green/white wire to the rear seat htr switch.

I haven't checked the relays. I I will see if any next to it are the same and try swapping.
https://uploads.tapatalk-cdn.com/201...84df55caeb.jpg
I saw this on here, I will double check the bentley manual also.


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That picture is correct, the missing relay is the one you need to have.

Use the relay from the rear window defroster next to the seat heater relay to test. They are the same.

Ok thanks. I'll try that.


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Ok guys. Swapped the rear seat heater relay with the rear window. No dice, still no heat on the rear seats. What gives?
What else can I try?


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check for power on the green/white wire going to the switch

Anyone got a pinout for that switch?
Trying to figure out how exactly it functions

here ya go... switch S68 is the left switch...
https://i.ibb.co/TvgD3NG/Rear-Seat-Heat.jpg

Thanks guys, I've been staring at this chart for a while but not knowing how to read the diagrams fully I can't quite figure it out.

I'm not sure about these symbols

https://i.ibb.co/G3rKds3/Screenshot-...159-Chrome.jpg

One of them might be a thermostat responsible for turning off the heat when it gets too hot?

My goal is to make the seats activate when the car is started with a remote.

So I understand the switch has 5 pins.

Pin 1 heats the backrest
Pin 2 heats the back seat
Both activate when key is in 2nd position
Pin 3 is ground
Pin 5 is another power from the relay

Do pins 1 and 2 get their power from K93 relay as well?

Pin 4 goes to the light control module Pin 1, which is
1 A Signal line, night lights Connector terminal 58

Am I correct to assume that the light module simply lights up the botton?

My best guess how this works is that pins 1 and 2 get power from pin 5, when the button is pressed, and if the key is in position 2.

Please correct me if I'm wrong about any of the above.

Terminal 58G from LCM is instrumentation lighting = only button back light.

Terminal 15 = ignition switch pos. 2 activated voltage supply. Comes to pin 5 via unloader relay.

Pin 2 is NTC resistor = temp sensor

Pin 3 is ground (Terminal 31).

The button has semiconductor FET:s to give supply voltage to heater pads. Depending on switch position the supply is cut when set temp is reached.

In this case if I connect an ignition wire from the remote to pin 1, it should activate the heated pads?

Yes, but the elements would be on full power (without temp regulation) until you turn them off.

I think that should be fine since the remote would be on for about 30 min

Just confirming that this seems to work.
I haven't been able to run the car for too long, it's still in my garage and I can't take it out yet.

But when I remote start, wire #5 gets 12 volts and the seats start warming up. Actually I get 11.75 volts on wire #5. If however I press the button for the heated seat, voltage on wire 5 jumps to 12.5.
Now I need to do the same for front seats, and maybe steering wheel and rear defrosted if possible.

I'm not a big fan of remote starters but I would think that a modern one would have some outputs to activate heated stuff and A/C ??

It has tons of outputs on the remote starter but the question is where to connect it to activate the button :)
There's many outputs for 500 mA positive and negative etc.

Haha, yes now I see what you mean! The button is in the controller module so you would probably need to take it apart to gain access. You might be able to get away with bypassing to full power with the seats and steering wheel but I wouldn't try it with the rear defroster.

Disassembly was rather simple

https://i.ibb.co/jhRHR8K/20211012-183922.jpg https://i.ibb.co/rbBRkzb/20211012-183839.jpg https://i.ibb.co/3fK77V8/20211012-183604.jpg https://i.ibb.co/yBm4CCd/20211012-183541.jpg
I take it you meant soldering something on the board to activate the heated function instead of providing direct voltage to pin 1?
This seems too advanced lol!

Yes, just add a wire that does the same as the switch.
You could use a small relay to bypass the button entirely or measure the voltage across the button pins when on/off and duplicate that with an output(power or ground, maybe a resistor needed) that you have available.

Thanks for the advice. Might be an overkill for my abilities and need though, but I'm sure it can help someone in the future.

I think I'm happy with providing 12 volts to pin 1 on the switch while the car is remote started. Once I get inside the car and start driving, the remote obviously disconnects/cuts out power output and the rear heated seats can be regulated with the button by the passengers.

Next on to the heated steering wheel.
Trying to figure out the diagrams.

https://i.ibb.co/1GHqXML/Screenshot-...040-Chrome.jpg https://i.ibb.co/b3GFRDP/Screenshot-...842-Chrome.jpg https://i.ibb.co/nD8Kc5B/Screenshot-...854-Chrome.jpg

Connector X01033 is the one I need I believe.
Now it seems pin 1 & 2 are connected to a heating element. So I guess there are 2 heating elements inside the steering wheel.
Pin 3 goes to a symbol that I don't know.
Pin 4 is obviously ground

I guess I need to provide 12 volts 10 amps to pin 1&2 to activate heated steering wheel.
Not sure about pin 3.
Will experiment and report back.

Pin 3 is a temp sensor /overheat switch.

Does it turn off heat to the steering wheel at a certain temperature? How does it do it? It doesn't seem to cut off power to the heating elements.

I found a decent video describing the insides of the steering wheel with emphasis on the heating element
https://youtu.be/PBcHi_NPPwc

Just tried connecting a 12 volt 1 amp adapter to I01033 connector. The steering wheel started warming up slowly. It definitely works.
https://i.ibb.co/mRr9THK/20211013-071224.jpg
It's kinda clear now. Red and brown wires get the juice from clockspring and pass it over to the connection with two blacks, one brown and one black and white wires. They connect directly into the filament that runs through the steering wheel.
The connector with green, yellow and blue wires connects to the steering wheel heating switch.
When the heating button is pressed, Steering wheel heating control unit probably allows voltage to go from red and brown wires to the 4 wire connector.

Because the button is separate from the controller this would be a good time to activate the controller instead of by-passing it. Because the controller is in the steering wheel though you have a problem with getting any extra connections to it unless there are some unused tracks in the clock spring.

Figured out the rear defrost.

https://i.ibb.co/Sx1j7dM/Screenshot-...743-Chrome.jpg

To activate the rear defrost, you can activate the defrost relay by providing negative to pin 7 on the picture.
So I simply spliced "ground when running" into pin 7 from my remote starter to activate the rear defrost.

Now the only problem is the steering wheel.

The problem with the steering wheel is that I can't even run wires inside as I wanted, because of course it rotates lol.
Any ideas how to do it through the clockspring?

After much pain I think I figured it out.

https://i.ibb.co/yPFCNzK/20211025-233228.jpg https://i.ibb.co/f1JQyBn/20211025-232604.jpg https://i.ibb.co/0Qj75Fb/20211025-232557.jpg https://i.ibb.co/ThKtY1z/20211025-232113.jpg https://i.ibb.co/jk6tsdS/20211025-232532.jpg

#1 is the connector that connects to the heating element of the steering wheel
#2, red and brown wires, provide power to #1
#3 provide power to #2
#4 is the connector that goes into #3

#4 connector consists of 2 wires. Brown and green/black. It provides power. However I'm not sure why power wires is green and black and not red.

Now I spliced into the green wire with 12 volts on remote start of the car. If my theory is correct, it should work.

But I'm thinking I must've overlooked something.