Description
Genuine Mack OEM brake light pressure switch (1MR2472M) for Mack heavy-duty trucks. Wired into the stop-lamp circuit, this normally-open switch closes at 4.0 PSI to illuminate the brake lights when the service brakes are applied — a non-functioning switch is both a safety risk and a DOT out-of-service violation. The 1/8″ NPT body ships with factory Loctite for a leak-free install. PAI FSW-0491 is the verified premium aftermarket equivalent.
Signs You Need a New Brake Light Pressure Switch
- Brake lights fail to illuminate when the pedal is applied
- Brake lights stay on continuously regardless of pedal input
- Intermittent operation — brake lights only at hard pedal pressure
- DOT roadside out-of-service citation for stop-lamp failure
Specifications
| Manufacturer | Mack Trucks (OEM) |
|---|---|
| Part Number | 1MR2472M |
| Part Type | Brake light pressure switch, normally open |
| Activation Pressure | 4.0 PSI |
| Thread Size | 1/8″ NPT (factory Loctite) |
| Connector | Rectangular |
| Overall Length | ~5.97 in |
Cross References
This part replaces or is equivalent to the following part numbers:
- Mack: 1MR2472M, 25165689
- PAI Industries: FSW-0491
Applications
Used across the Mack heavy-duty truck range — the 1MR2472M is the stop-lamp pressure switch on most Mack air-brake circuits, including:
- Mack Anthem, Pinnacle, Granite, TerraPro
- Mack CH, CL, CV, CX series
- Mack RD, R Model — selected applications
Confirm thread size (1/8″ NPT) and 4.0 PSI activation match your circuit before ordering. Note: Mack 1MR2472M2 is a different part (A/C pressure switch, PAI LSW-0967) — the trailing “2” matters.
