Third Row

Last updated: October 20, 2023

Overview

The Model X 6 and 7 seater options are equipped with a third row. The six person seating capacity has a driver and passenger seat in the front row, a two person second row in which there is a left and right monopost seat, and a two person bench style third row. The 7 person seating capacity has a driver and passenger seat in the first row, a three passenger bench seat (with the capability to slide and pivot forward), and a two person seating capacity third row.

Covers

Component Description

Model X seats are available in cream, white, and, black polyurethane (PUR). This material is a leather alternative.

Theory of Operation

Model X third 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 backrest substrate allowing the seat back 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.

Serviceability

Cleaning

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

For CREAM PUR ONLY, isopropyl alcohol is the strongest solvent that can be used without damaging the seat material. Moisten a soft cloth with warm water and isopropyl alcohol and gently wipe the stain in a circular motion.

Warning

Isopropyl alcohol should not be used on Black PUR.

Servicing Covers

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/Pad

Component Description

The seat foam, also referred to as the seat pad, provides comfort and stability to occupants.

Serviceability

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 install. 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 Heat

Component Description

Model X third row has heating elements in each of the cushion seating positions as well as the backrests.

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 Operation

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.

Communication

The seat heater communicates via Vehicle bus (VEH). The seat cushion and the 60% seat back is controlled by the left vehicle controller (VCLEFT). The seat back fo the 40% seat is controlled by the right vehicle controller (VCRIGHT). Below illustrates which seat heater positions communicate on which vehicle controller.

Serviceability

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 Sensing

Each seat in the third 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.

Theory of Operation

Occupancy sensing for the third row communicates to the right side vehicle controller (VCRIGHT). 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.

Serviceability

Having the sensors distributed throughout the cushion helps to prevent situations where small items might trigger the seat belt reminder indicator. The resistive pad, or seat belt reminder, located in the third 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.

Frame

Component Description

The third row is comprised of one frame in which each backrest can fold flat individually. While the frame is one assembly, there is a bench cushion assembly and an individual cover/foam stack up for the backrests.

Theory of Operation

The third row frame allows for two positions, upright and fold flat. There is a seat back stopper that prevents the backrest from over travel in the upright position and a fold flat endstop to prevent the backrest from over travel when folding flat. These stoppers are located on the outboard portion of the seat frame for either backrest. The seat back stopper is located forward of the recliner assembly and the fold flat end stop is located rearward of the recliner assembly. The recliner assembly is made up of the recliner disc and the recliner lever. When the recliner actuator is energized, it pulls the recliner lever moving the disc out of place allowing the backrest to move freely into one of the stopper before it locks again.

Located on the inboard of the frame is the clock spring which allows the back rest to dump forward.

Serviceability

Misalignment in the seat back can usually be pinpointed to how the frame is mounted to the body.

Trim/Plastics

Component Description

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 considered trim:

• Cup Holder
• Backrest Substrate
• Back Panels
• B-Covers
• Switches
• Escutcheon

Theory of Operation

Cup holder

The seat cushion is equipped with a 2 cup holders between the seats.

Backrest Substrate

The Model X third row seats keeps shape with the help of the plastic components that support the foam. The backrest substrate allows for the seat cover, pad, and occupancy sensors to form one assembly that can be easily removed and replaced.

Back Panels

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.

B-Covers

B-Covers are the plastic components that cover the recliner mechanism. This is an entirely cosmetic component as it's function is to ensure that no parts of the frame are visible to the customer in any of the seating positions. Because B-Covers are located around moving parts there is potential, if installed incorrectly or issues with manufacturing, that the B-Cover can cut or tear into the seat cover. Each portion of the frame the B-Cover conceals is made up of an inner and outer B-Cover in order to fully encompass the frame from being visible with the seat back in various positions.

Switches

Located on the inboard backrest, is the shoulder switch which sends a signal to VCRIGHT to activate the recliner actuator in order to unlock the reclining mechanism so that the backrest can fold flat. Both the left hand and right hand seats communicate via VCRIGHT.

Escutcheon

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.

Headrest

Component Description

Each of the seating positions is equipped with an adjustable headrest. Similar to the seat itself, there is a stack up of cover, foam, frame, substrate to maintain shape.

Theory of Operation

The headrest can adjust to one of two positions. The headrest frame moves up and down through the guide post in order to make adjustments. Depressing on the guide cap allows for the frame to move to one of the designated positions.

Serviceability

The headrest frame inside the guides can sometimes cause a squeaking or rattling noise, this can be resolved by either adding grease for squeaking or replacing the guides for a tighter fit to prevent rattling.

Actuators

Recliner Actuators (x2)

Component Description

The third row is equipped with a recliner actuator located at the bottom of the seat back for each of the seat positions.

Recliner Actuators

Theory of Operation

The recliner actuator is directly connected to the recliner lever. When the actuator is momentarily energized, it pulls the lever up allowing the backrest to unlock and fold flat. There are recliner levers on both the inboard and outboard sides of each seating position, the cables route up and then back down to the recliner lever located at the junction of seat back and cushion. When the backrest is positioned into the upright position it is ready to lock again.

Serviceability

The actuators communicate on VCRIGHT, be sure to check communication and then proper tension within the actuator cables.

Linear Headrest Actuator (x2)

Component Description

The linear headrest actuator allows the headrest to unlock and therefore fold down in order to have more room during storage.

Headrest Actuator

Theory of Operation

The headrest actuator is activated when the seat is triggered to fold flat. Located at the bottom of the seat back rest the cable routes to the left headrest guide pole and releases the headrest allowing it to be free moving.

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