Overview
The TDK-904 is a two-button dashboard switch used on CNG and bi-fuel commercial vehicles, construction machinery and new-energy platforms. It combines two driver controls that a natural-gas vehicle needs on the same fascia: a CNG fuel-mode selection and an ESP (stability control) off button. Both are illuminated — a white backlight makes the buttons visible at night, and an amber indicator lights when the vehicle is running on gas — and both run on the vehicle’s 18–32 V system.
It is a signal-level switch: each button reports the driver’s selection to the vehicle’s controller on a dedicated signal line rather than switching the fuel solenoid or the ESP actuator directly. The two functions, the pin assignment and the cap markings summarised in the tables below are read from the part’s own schematic, load table and bill of materials.
The two buttons
The TDK-904 carries two independent buttons on one bezel:
| Button | Marking | Function |
|---|---|---|
| CNG | “CNG” text cap | Selects the fuel mode — conventional fuel or CNG (compressed natural gas). Reports the “gas” selection on the gas-signal line; the amber indicator lights in gas mode. |
| ESP off | Car-with-skid-marks icon, slashed | Requests ESP (electronic stability program) off — the ESP-off request is reported to the vehicle on its own signal line. |
The two functions are unrelated — one manages the natural-gas fuel system, the other the stability system — and the TDK-904 puts both on a single dashboard switch so a CNG / bi-fuel cab needs one fascia opening instead of two. The buttons take a defined 5 ± 2 N press and are rated for more than 30,000 operations. A white backlight keeps them legible in a dark cab; a separate amber indicator lights when the vehicle is running on gas. On the part’s own circuit diagram this gas indicator is the only lit-state confirmation shown, so whether the ESP-off state carries its own indication is confirmed per programme.
Connector & wiring
Both signals plus the ignition feed, backlight supply and ground share a single 6-way connector; the mating half on the harness side is an AMP 1419158-1. The pin assignment read from the switch schematic is below — final harness colours and any pull-up values are confirmed at RFQ.
| Pin | Function | Direction |
|---|---|---|
| 1 | ESP-off signal | Output to controller |
| 2 | Not connected | — |
| 3 | Backlight supply | Input |
| 4 | Ground (GND) | — |
| 5 | IGN (ignition) power | Input |
| 6 | Gas-mode (CNG) signal | Output to controller |
Because both outputs are signal lines rather than power switches, the TDK-904 drives a controller input — it does not carry the current of the fuel solenoid, the gas injectors or the ESP hydraulics. Tell us the controller and signal levels your platform expects and we confirm the interface at RFQ.
Mounting, materials & manufacturing
The TDK-904 is a panel-mount module that snaps into a dashboard opening from the front. The front bezel measures about 42.3 × 24.6 mm, the outer body is about 45 mm wide and 52.9 mm tall, and it sits roughly 22.6 mm deep behind the panel to the base of the connector. Confirm the exact cutout and retention against the current drawing with your RFQ.
The two caps are moulded in PC, the body and base in ABS+PC over an FR-4 PCBA, with a spring-steel return spring under each button. It is built under IATF 16949 with APQP planning and a PPAP package available for OEM programmes; end-of-line testing follows the programme’s control plan — typically continuity, actuation and illumination — while endurance, temperature soak and sealing are checked on a sample basis in our in-house lab when a programme calls for fresh qualification. Substance and flammability compliance is confirmed to the programme’s requirements.
Where it fits
The TDK-904 belongs to the Switches & Sensors family of cab discrete controls. It sits alongside the other dashboard switches — for grouped lighting and instrument control see the EDK-2006 light & instrument switch; for the driver’s start control see the TDK-902 / 905 engine start-stop button; and for the round illuminated button and the pre-ignition switch see the TDK-2513 / 2514 cab switches. Each is an operator input; the vehicle’s controllers act on the signal. For how these hard-wired signal switches sit against LIN and CAN alternatives when you plan a cab, see the Switches & Sensors buyer guide.
Common questions from buyers
Does it switch the fuel solenoid or the ESP system directly? No. The TDK-904 is a signal switch: it reports the driver’s CNG and ESP-off selections to the vehicle’s controller, which then acts on the fuel or stability system. It does not carry that load current.
Which connector do I order against? The switch wires through a 6-way connector whose harness-side mating half is an AMP 1419158-1. The pin assignment (ESP-off signal, backlight, ground, ignition power, gas-mode signal) is in the table above — send your harness plan and we confirm colours and the final assignment.
Can the cap markings or the second function be changed? The TDK-904 is built as a fixed CNG + ESP-off pair. Different artwork or a different second function is a programme change — scoped with tooling, MOQ and an interface review — not a catalogue option. Send the artwork, the panel drawing and the controller interface with your RFQ.
How to ask
The TDK-904 belongs to the Switches & Sensors family. Tell us your target vehicle programme, the system voltage, the controller interface and expected annual volume — and we confirm the connector pinout, the cap markings and the sealing level. Use the contact page; drawings welcome.
