Every window that goes up, every door that locks and every mirror a driver aims on a truck, bus or car starts at one part: the switch on the door armrest. It is easy to treat it as a commodity rocker, but on a modern cab it is a networked switch panel with a LIN data line, defined operating force and endurance, and a connector that has to match either a local door harness or a door control module. Getting it wrong shows up as a switch that will not drive the motor it was wired to, or a 24 V panel dropped onto a 12 V body.
This guide is the switch-side companion to the power window & door control module buyer guide. That guide covers the controller that drives the motors and where anti-pinch lives; this one covers the part the driver touches, and how a buyer picks between the three LIN door switches Youlai builds — the EDK-908, the EDK-914 and the TDK-2202/3. It assumes you know what a door armrest switch is for and are deciding which one a cab door should carry.
1. What a cab-door switch panel does
A cab-door switch panel is the driver-facing input for the cab's window, lock and mirror controls. It gathers the keys a driver reaches for (window up and down, central lock and unlock, and on a full master switch the mirror adjust and mirror defrost) into one unit at the armrest, and turns each press into a clean signal. On the Youlai LIN door switches that signal travels two ways at once: the panel has its own switching outputs so it can drive local loads directly, and it carries a LIN data line so it can also sit on the cab's low-speed network and report to a body or door controller.
That dual nature is what separates a networked door switch from a plain rocker. A LIN line runs at low bandwidth and only needs to reach the body control module (BCM) or door controller, which is exactly right for door functions where the data is small (switch state, motor direction) and the loads are local to the door. It is the same partitioning described in the Switches & Sensors technical guide: interior door, window and mirror switching runs on short hard-wire outputs and LIN, while the high-speed CAN backbone is kept for functions that need it, since a control only the door uses does not warrant its own CAN node. For how LIN sits against CAN and plain hard-wired switching across a whole dashboard, see CAN vs LIN vs hard-wired switches.
2. Three LIN door switches at a glance
Youlai builds the door switch input at three points, and they are not interchangeable; they separate cleanly by system voltage and by how much of the door the panel controls. The table below is the fastest way to see where each one sits before the detail in section 3.
| Switch | System | Function scope | Drive path | Endurance / IP |
|---|---|---|---|---|
| EDK‑908 | 24 V (18–32 VDC) | Full master: window · central lock · mirror adjust · mirror defrost | Direct outputs + LIN (local drive, or reports to door module per programme) | > 50,000 ops · IP per programme |
| EDK‑914 | 24 V (18–32 VDC) | Leaner: window up/down + central lock (single- and dual-button variants) | LIN + window/lock switching (motor path direct or via module per programme) | > 50,000 ops · IP53 |
| TDK‑2202/2203 | 12 V (9–16 VDC) | Window + central lock; driver master + single-window switch set | Direct 25 A window-motor drive + LIN for lock / door coordination | 30,000 ops · interior (IP per programme) |
All three share the same LIN-plus-local-output idea and the same 5 ± 1.5 N key action, so the choice is not about switch quality; it is about matching the door. Read the table left to right: voltage first, then how much of the door the panel owns, then whether it drives the motor itself. Those three columns settle almost every case.
3. What actually decides the choice
Three parameters do almost all the work. Take them in order and the part number falls out.
System voltage is the first fork
A 24 V system (heavy trucks, buses and most construction machinery) runs the EDK-908 or EDK-914, both specified for an 18 to 32 VDC working range. A 12 V system (most passenger cars and light vehicles) runs the TDK-2202/3 set at 9 to 16 VDC. The EDK-908B is a separate door and window switch at 9 to 32 VDC, with one CAN line and one hardwire line at 24 V / 500 mA. What decides this is the cab's low-voltage electrical system, not the powertrain: an electric or hybrid vehicle can be built on either 12 V or 24 V, so confirm the body-electrical voltage rather than reading it off the drivetrain. Either way it is not a preference; the motor circuit rating, the quiescent draw and the connector pinout are all set to the system voltage, so a switch built for one will not simply work on the other. Settle voltage before anything else — our 12 V vs 24 V systems guide covers how that choice propagates through the rest of the vehicle.
Function scope decides how much door the panel owns
On a 24 V cab the second question is how much of the door the armrest controls. The EDK-908 is the full door and window panel: window lift, central lock, mirror direction and mirror defrost. The EDK-914 strips that back to windows and central lock in single- and dual-button variants, for a door where a separate mirror switch handles the mirrors or the cab has no powered mirror set. Choosing the EDK-914 where the full master is not needed keeps the key count and the connector honest; choosing the EDK-908 where the door owns the mirrors avoids bolting a second switch onto the armrest.
The drive path decides whether the switch carries the motor
The last question is whether the switch drives the window motor itself or hands off to a door control module. The 12 V TDK-2202/3 master switches the window-motor circuit directly (rated to carry 25 A). Above 12 ± 0.7 A it opens its relay within 3 s, and a window command held longer than 10 s opens the same relay. This is a switch that carries current. On a 24 V cab the split is set per programme: the EDK-908 has its own window, lock and mirror outputs and can drive those loads directly on a local harness, while the EDK-914 carries the window and lock switching plus LIN, and whether it switches the motor on its own outputs or commands a door module is confirmed against the harness. On a networked cab either switch reports over LIN to a door module that owns the drive. One honest limit worth stating up front: torque-based anti-pinch with self-learning is a module function, not a switch function.
4. Feel, travel, endurance and sealing
The three LIN switches in the table each use a 5 ± 1.5 N key action. The EDK-914 key travel is 15°. The EDK-908 travel is agreed per programme.
The EDK-908 is a door-panel control whose protection rating is confirmed per programme. The EDK-914 carries IP53 (dust-protected and guarded against water sprayed at up to 60° from vertical), and the TDK-2202/3 is an interior part with its sealing class confirmed per programme. Working temperature is −40 to +85 °C on the EDK-908 (storage −40 to +90 °C), −30 to +85 °C on the EDK-914 (storage to −40 °C), and −40 to +80 °C on the 12 V TDK set.
5. Where each switch fits on real vehicles
The same door functions read the same on a spec sheet across vehicle types, but the platform decides which switch answers.
- Heavy trucks and buses (24 V). A tractor or coach cab with powered, heated mirrors and central locking on the driver's door is the classic EDK-908 case — one panel owning windows, lock and the mirror set, with its own outputs and a LIN line. On a bus the driver-door switch commonly reports over LIN to a networked door module, which then coordinates with the passenger-door systems on the vehicle's wider body network.
- Construction machinery (24 V). A cab that needs its windows and central lock but has fixed or manually adjusted mirrors is a good fit for the leaner EDK-914 — the same 18–32 V LIN family without the mirror outputs, in single- or dual-button form to match a one- or two-window door.
- 12 V passenger and light vehicles. A 12 V body with a driver master controlling several windows plus central lock, and a single-window switch on the passenger doors, is the TDK-2202/3 set. Its 25 A direct motor drive suits a vehicle where the switch carries the window motor rather than a separate module doing it. On an electric or hybrid vehicle, confirm whether the body system is 12 V or 24 V first: a 24 V electric platform points back to the EDK parts.
- Doors that only raise a window. Where a single door needs nothing more than window up and down plus a lock, the single-button EDK-914 variant avoids paying for a master-switch key count the door will never use.
6. The switch and the door module are two parts, not two options
The most common mix-up in this category is treating a door switch and a door control module as alternatives. They are two halves of the same door sub-system. The switch is the driver-facing input; the module is the controller that reads switch inputs, drives the window, lock and mirror motors, carries the motor-drive protection and links to the body network over CAN. On a simple local harness a switch such as the EDK-908 can drive its loads directly and there is no separate module; on a networked cab the switch provides the controls and a module such as the EBX-2163 door & window control module owns the logic and the drive, with the split confirmed per programme. Anti-pinch and self-learning travel calibration are module functions: only the controller that drives the motor can sense a jam and reverse it. The EDK-908 publishes motor over-temperature protection on its own outputs; the module adds the motor-drive protection on the loads it drives. For that half of the decision, dedicated module versus BCM versus switch panel and where anti-pinch belongs, see the power window & door control module guide.
7. How to write a specification a supplier can quote
A door-switch requirement a supplier can quote against, rather than guess at, covers five things. Leaving one blank is what turns a quick quote into a round of questions.
- System voltage. 12 or 24 V nominal and the tolerance band. This is the first fork: 12 V points to the TDK-2202/3 set; 24 V LIN points to the EDK-908 or EDK-914. The EDK-908B is specified at 9–32 V.
- Function scope on the door. Windows only, windows plus central lock, or the full window / lock / mirror-adjust / mirror-heat master. State each function, because it sets the key count and the connector size.
- Drive path. Whether the switch drives the window motor directly (as the TDK-2202 does at 25 A) or reports to a door control module over LIN. This decides the switch's output stage and its role in the harness.
- Button layout and legend. Single- or dual-button, driver-master versus single-window, and the ISO 2575 key symbols, backlight and language for your market. This is the part most often left to "standard" and then reworked.
- Connector and pinout. The parts use different housings (an 8-way plus 10-way pair on the EDK-908, a 16-way master plus 8-way single on the TDK-2202/3, and a per-programme connector on the EDK-914), so name the target harness or ask us to confirm it against the door module.
The item buyers skip and regret is the drive path in point three. Whether the switch carries the motor or reports to a module changes the output stage, the connector and the way the door harness is drawn; deciding it after the harness is designed is expensive. Settle it with the function scope, not after.
8. What to look for in a supplier
A door switch is touched thousands of times a year, carries a LIN line onto the cab network and, on a 12 V master, switches the window-motor current itself. The supplier questions that matter are about capability and honesty, not headline price.
- Endurance and feel testing. The 50,000-operation (24 V) and 30,000-operation (12 V) ratings only mean something if they are verified. A supplier should describe the contact make/break, operating-force and LIN-communication checks it runs, and confirm endurance on a sample basis rather than quote a number off a datasheet.
- Motor-circuit rating, where the switch drives loads. On a direct-drive master like the TDK-2202 the 25 A carry and the relay trip need a genuine contact and terminal design behind them. Ask how the switched motor circuit is rated and protected.
- Key legend and connector customisation. The switch's whole job is to fit your door, so the legend set, backlight scheme, button layout and connector are expected programme variables rather than exceptions. Ask early what a key-map or connector change means for tooling, minimum order and validation, so the cost and lead time are clear before nomination.
- Standards and EMC capability. Confirm in-house EMC pre-compliance and environmental testing rather than outsourced-only validation. Youlai validates in an in-house environmental laboratory with EMC pre-compliance equipment, and customer or destination-market standards are confirmed per project.
Quality system and PPAP level are on the IATF 16949 and OEM sourcing pages.
If you are scoping the door armrest, the most useful things to bring to a first conversation are your system voltage and your function scope from section 7 — whether the door needs the mirrors, whether the switch drives the motor or a module does, and the button layout you want. On 24 V LIN that maps onto the EDK‑908 or the EDK‑914; on 12 V direct-drive, the TDK‑2202 / TDK‑2203. The EDK-908B is a separate 9–32 V switch on the EDK-908 page, not this LIN pair. Either path also tells us if the key map falls outside those platforms.
For drawings, a key-legend and connector review or a sample request against your vehicle programme, please use the contact page or message +86 134 6767 4786 on WhatsApp. Typical reply within one business day.