Second Rowlink
Last updated: January 06, 2025
Overviewlink
Model 3 (2024+) has a standard 5 person seating capacity with a driver and passenger seat in the front row and a three passenger bench seat with backrests that fold flat in the rear. Seats come with white or black color options. The second row seats do not have ventilation, but do have seat heating (except for the center seat).
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| Second Row Seats |
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| 1. Cover 2. Heat Pad 3. Occupancy Sensors 4. Foam/Pad 5. Seat belt buckle 6. Center Seat Belt Retractor 7. Seat Frame 8. Headrest 9. Seat Audio/Microphone 10. Wire harness 11. Seat plastics 12. Back Panels |
| Second Row Seats |
The seat sections are referred to as 40% (right-side rear seat) and 60% (left-side and middle rear passenger seats).
Coverslink
Component Descriptionlink
Model 3 (2024+) seats are available in white and black polyurethane (PUR). This material is a leather alternative. When surfaces of the seat back contact one another, one side is a cloth material, while the other side is PUR. This is to reduce noise issues that are typical when PUR rubs against itself.
Theory of Operationlink
Model 3 (2024+) second row seat covers are secured to the foam with a combination of hog rings and hook-and-loop fastening strips. Then sandwiching the foam, the cover is attached to the upholstery support allowing the seatback to maintain shape prior to attachment to the seat frame. There is also stitch detailing within the seat to help form the shape around the foam.
Serviceabilitylink
Cleaninglink
Cleaning PUR seats with some conventional cleaners (especially alcohol-based) can cause performance and appearance degradation. Do NOT use products containing bleach (sodium hypochlorite). It is therefore important to clean seats with only approved cleaners. Below is a list of approved cleaners:
- Clorox NON Bleach Disinfecting Wipes
- Formula 409
- Seventh Generation NON Bleach Disinfecting Wipes
Servicing Coverslink
Hog rings must be installed using hog ring pliers to crimp the ring in order to securely fasten it the cover to the foam.
Hog rings are a consumable part, as with every removal they need to be cut.
Craftsmanship is extremely important when dealing with installing covers to ensure that there are no wrinkles or puckers in the material.
Foam/Padlink
Component Descriptionlink
The seat foam, also referred to as the seat pad, provides comfort and stability to occupants.
Serviceabilitylink
If the seat foam and covers have not been installed appropriately it can feel or look as if the seat is missing foam or that the foam has collapsed. Because the foam is sandwiched between the cover and upholstery support, it is possible that it could have been misaligned during installation. In some rare cases, the way in which a customer ingresses or egresses from the vehicle can apply pressure on the outmost edge of the cover and foam, causing the foam to get caught on the upholstery support and not maintain it's full shape. This can be resolved by refitting the cover and foam.
Seat Heatlink
Component Descriptionlink
Model 3 (2024+) second row has heating elements in the left and right seats, both cushion and backrest.
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| Second Row Seat Heat |
The seat heater is made up of the following components:
- High side driver
- Pulse width modulation (PWM)
- Negative temperature coefficient (NTC) thermistors
- Resistive pad
The heating element, or resistive pad, is located only in the center panels of the seat back and seat cushion, the heating element is not located in the side bolsters.
Theory of Operationlink
There are 3 heating temperature targets for the seats (low, medium, and high). Target temperatures for both the cushion and the backrest are:
- Low (Setting 1): 28C or 82F
- Medium (Setting 2): 44C or 111F
- High (Setting 3): 60C or 140F
The seat heaters utilize PWM at 1Hz in order to reach the desired target temperature. This means pulsing the voltage at a controlled frequency. The duty cycle (width of the pulses) will be increased if the temperature read by the NTC is below the target temperature, the duty cycle can be increased all the way up to 100%, providing up to 16V. When the temperature read by the NTC is higher than the target temperature, the duty cycle can be decreased all the way to 0% providing no voltage. Due to this PWM, the voltage at the seat heater is constantly changing and varies due to ambient temperature and heat setting level.
Current travels through the resistive pad generating the heat. This resistance remains constant with a functioning seat heater.
The NTC is located only in the seat cushion, not the seat back. It is connected to 5V through a resistor on the body controller. As the temperature of the seat increases, the resistance on the NTC lowers and the voltage read at the controller goes down. If the thermistor is disconnected, the voltmeter will read 5V or 0V depending on where the disconnect occurs. At around room temperature, the voltage at the NTC should be around 3.6V.
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| NTC Location |
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| NTC Schematic diagram |
Communicationlink
The seat heater communicates via Vehicle controller area network (CAN) bus. The seat cushion and the 60% seat back is controlled by the left vehicle controller. The seat back fo the 40% seat is controlled by the right vehicle controller.
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| Rear Seats Occupancy and Heat Communication Diagram |
Serviceabilitylink
The seat heater resistive pad is integrated into the seat cover and is therefore not serviceable.
The temperature felt at the surface of the seat, depends on an occupant sitting in the seat. Compressing the foam and trim with an occupant sitting in the seat allows for the occupant to fully feel the temperature provided by the seat. Factors such as a heat soaked interior, body heat from someone sitting in the seat, direct sunlight and ambient air temperatures can play a big role on the temperature readings at the surface of the seat cover.
Occupancy Sensinglink
Component Descriptionlink
Each seat in the second row contains an occupancy sensor, resistive pad, also referred to as the seat belt reminder (SBR). The occupancy sensors are located in the seat cushion. The occupancy sensors are switches distributed throughout the cushion connected in both parallel and series.
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| Restive Pad (x3) |
Theory of Operationlink
Occupancy sensing for the second row communicates to left vehicle controller. The sensor itself is a simple resistive pad that can be tested with a multimeter. Occupied, the resistance should read 1kOhm. Unoccupied, the resistance should read 11kOhm.
Serviceabilitylink
Occupant sensors distributed throughout the cushion help to prevent situations where small items might trigger the seat belt reminder indicator. At the time of publishing this document, the resistive pad, or seat belt reminder, located in the second row cushion is not a serviceable component. This is due to the infrequency of which this part needs to be replaced as well as current production capability.
Framelink
Component Descriptionlink
The second row is comprised of two separate backrest frames. The 60% and the 40%. The 40% contains the right hand second row passenger and the 60% contains the left hand and center passenger positions, with the center position being referred to as the 20%. For Model 3 (2024+), these structures are stand alone frames with the seat cushion bench being one piece that sits atop the penthouse.
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| Second Row Seat Frames |
Theory of Operationlink
The frame allows for the backrest to pivot about the bottom edge in order for the backrest to fold flat.
Serviceabilitylink
A spring is located on the outboard side of the seat, at the axis of rotation for the seatback to fold forward. This spring helps pop the seatback forward but does not cause the seatback to dump in a fold flat position.
Because the frame is a moving part, it can be the culprit to some noise issues, in these instances be sure to check all mating points to the body as well as the hinge point (axis of rotation).
Trim/Plasticslink
Component Descriptionlink
To limit confusion during diagnosis and when talking about the seats, trim is defined as the hard plastic parts on the seat. Seat pads and covers (the textile or leather seat material) is considered seat upholstery and should be referred to as such.
The following pieces are also considered trim:
- Back panels
- Escutcheon
Theory of Operationlink
Back Panelslink
The back panels for the second row are plastic components that conceal the wiring harness and backrest shell. The back panels also have a cut outs for child seat tethers. Removing the back panel will allow access to inspect components like the latch mechanism for first steps of diagnosis.
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| Back Panels |
Escutcheonlink
The escutcheon is the plastic bezel in which the center seat belt feeds through the backrest. The center seatbelt is the only retractor incorporated into the second row and the escutcheon acts as protection to the cover.
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| Escutcheon |
Actuatorslink
Component Descriptionlink
Model 3 (2024+) has a single latch mechanism that releases the seat back to allow it to fold flat. The actuator is integrated into the latch mechanism and can be serviced as one part.
The second row armrest has an actuator inside the armrest which triggers guide pins within the armrest that are lowered, allowing the armrest to fold flat.
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| Seat back latch |
Theory of Operationlink
Both the seatback latch actuator and armrest actuator communicate on the left vehicle controller. Integrated into the mechanism is a hall effect sensor which allows the firmware to distinguish if the latch is engaged or disengaged.
Armrestlink
Component Descriptionlink
The second row is equipped with an armrest at the center seating position. The armrest has a cupholder and a storage compartment with a lid. Between the armrest and the storage compartment is an inductive charger for two phones.
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| Second Row Seat Armrest |
Theory of Operationlink
The armrest communicates to the left vehicle controller for all of the controls. The inductive charger communicates via Local Interconnect Network (LIN). The actuator located in the armrest pulls two guide pins which allows the armrest to be free moving and only locks in the closed position.
Fold Flat Functionlink
Feature Descriptionlink
Fold flat is referred to the position in which the seatback is completely folded down and laying on top of the seat cushion. Fold flat can occur on the 40% or the 60%.
Theory of Operationlink
A combination of the latch hall effect sensor and the reading from the seat belt reminder will indicate if the seat is in the folded flat position.
A short press of an electrical switch causes the actuator to run full stroke. The electrical switch for this feature can be found in these locations:
- The rear compartment.
- The outboard shoulder of the rear seat.
After the short press, there is an in-rush current spike and shortly after, a stall current spike as the actuator hits the travel limit. When the actuator has reached the travel limit, the seat back is then able to be assisted into the fold flat position. The latch mechanism pushes the seat back forward but is not enough for the seat back to dump forward on it's own. When the switch is released, and the actuator is de-energized, the actuator is spring returned back into the extended state allowing the seat back to lock into the next available position.
The 60% and 40% sides can be adjusted via a lever that allows the seats to fold flat.
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| Seatback Release Latches |
Serviceabilitylink
When folding flat, there is a potential that the seatback can make contact with the rear load floor. Interaction between the seatback and the load floor can cause creasing in either the load floor or seatback panel.