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Heated seats stopped working on my wife's car a couple of weeks ago...
2010 C300 Sport:
a. When the either the driver or passenger switches are pressed, 3 red leds light up and then go off in a few seconds.
b. I get the following error from my iCarsoft MBII reader, B109512
c. Does any one have a picture of the under the seat element connector?
d. Or possibly the color of the wires?
I just read the code this morning but don't have car right now, I will have car back later today and hope to have a place to start. To test, I would just like to disconnect the passenger (right) seat heater first, then check to see if the driver's side comes back.
Based on your VIN the R and L seat and backrest heaters are separate and receive voltage from the rear SAM. The R seat wire colors are 2(blue) and 1(brown). The L seat is 1(brown) and 2(blue)--the browns are the grounds. Therefore if you disconnect a section of one seat the other sections will not be affected, however when you do so you will induce a fault.
The heater part numbers are R=204 910 59 30 9D88 and the L=204 910 19 46 9D88
With the colors of the heating pad wires known, here is what I did:
a. Tested resistance of each seat’s heating pads. 2 pads per seat and the wires for each pad terminate into a single 2 pin connector.
Left side: 24.9 ohms
Right side: 13.8 ohms
Definitely a significant difference in resistance.
b. Then I did different operational tests for both sides of the seat heaters. I reset the errors each time I tried something different and proceeded to turn the ignition key off and then starting the car every time. Each time I turned on the left side switch on first then the right side. Each time the 3 LEDs light briefly and then go off for both sides.
Test 1: Disconnected the right-side heating pads with the left heating pads connected. Same error – right side shorted to positive
Test 2: Disconnected the right-side heating pads and the main right seat power connector with the left heating pads connected. Same error – right side shorted to positive
Test 3: Disconnected the left side with the right side connected. Same error – right side shorted to positive
Test 4: Disconnected the right-side heating pads with the left heating pads connected. Attached a voltmeter to the connector that would be powering the right seat pads when the switch is turned on. When I turn on the right-side switch, the voltmeter briefly goes to 12.01 volts then immediately to zero volts and the LEDs go off. Same error – right side shorted to positive
Test 5: Disconnected the right-side heating pads with the left heating pads connected. Attached a 1156 light bulb to the connector that would be powering the right seat pads when the switch is turned on. When I turn on the right-side switch, the light bulb briefly turns on then immediately goes off and the LEDs go off. Same error – right side shorted to positive
Test 6: Disconnected both left and right-side heating pads. Turned on switches and same thing behavior happens. Same error- right side shorted to positive
Test 7 and 8: With all power off in the car, I did a resistance check of the wires that power the seat pads on both sides, both sides displayed and open connection between the two pins. The right side was the same, no short or difference resistance from the power source.
Seems that no matter if the heating pads are connected or disconnected, the same error is logged after each test. I double check when I clear the errors to re-read them to ensure no errors appear before the start of each test.
I would have expected to see different error messages when the pads were disconnected. Could I have more than one problem? Possibly something wrong with the rear SAM, the circuit controlling the seat heaters? Definitely the difference of static resistance between the left and right side seats is a problem, but before changing out the right side heating pads, I want to be sure.
03-01-2018, 10:49 AM
