Overview
The ZF 0501.311.444 THERMO-SCHALTER is a critical thermal management component engineered specifically for the WG65 and WG251 series transmissions. This OEM genuine part, identified by SKU 0501.311.444, functions as a temperature-sensitive switch that monitors and regulates hydraulic fluid temperature within the transmission housing. Positioned directly in the valve body or main control assembly, it activates or deactivates the cooling circuit to prevent thermal degradation of the transmission fluid. When fluid temperatures exceed optimal thresholds, this switch triggers the cooler bypass, ensuring the transmission operates within its designed thermal window. The TRANSMISSION HOUSING provides the structural foundation for this component, while the HEXAGON SCREW secures the assembly in place.
Symptoms of Failure
- Erratic shifting or delayed engagement: A failing thermo-switch may cause the transmission to shift harshly or hesitate when engaging gears, as incorrect temperature signals disrupt hydraulic pressure regulation.
- Overheating transmission fluid: If the switch fails in the closed position, the cooling circuit remains inactive, leading to chronic overheating and burnt fluid odor.
- Constant cooler bypass operation: A stuck-open switch forces the transmission to run continuously in cool-down mode, reducing operating temperature and causing sluggish performance or increased fuel consumption.
- Intermittent warning lights: Faulty temperature readings from the 0501.311.444 can trigger dashboard transmission temperature warnings without actual overheating.
Technical Specifications
| Parameter | Value |
|---|---|
| OEM Part Number | 0501.311.444 |
| Material | Brass housing with bimetallic strip |
| Weight | 0.12 kg (0.26 lbs) |
| Thread Size | M14 x 1.5 |
| Operating Temperature Range | -40°C to +150°C (-40°F to +302°F) |
| Switch Point (Open/Close) | 85°C ± 3°C (185°F ± 5°F) |
| Max Torque | 25 Nm (18.4 ft-lbs) |
| OEM Reference | ZF 0501.311.444 |
Compatibility
This genuine ZF thermo-switch is designed for use in the WG65 and WG251 transmission series. It is also compatible with the WG180, WG200, and WG250 models that share the same valve body architecture. The HOUSING and HOUSING components from these series provide the mounting interface for this switch. Always verify your transmission model and serial number before installation, as variations exist between early and late production units.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616101111 | TRANSMISSION HOUSING | Main structural casing for the transmission assembly |
| 0636011118 | HEXAGON SCREW | Fastener for securing transmission components |
| 4616301304 | HOUSING | Intermediate housing for valve body mounting |
| 4616301309 | HOUSING | Secondary housing for auxiliary components |
| 0636011038 | HEXAGON SCREW | Mounting screw for thermo-switch bracket |
| 0636016015 | HEXAGON SCREW | High-torque fastener for housing connections |
| 0631306085 | CYLINDRICAL PIN | Alignment pin for precise component positioning |
| 0634313118 | O-RING | Seal for fluid-tight connections |
| 0636304019 | SCREW PLUG | Port closure for test points or drains |
| 0634801152 | SEALING RING | Gasket for preventing fluid leaks |
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