Dorman 904-386 Diesel Exhaust Fluid (DEF) Heater

Overview of Dorman 904-386 Diesel Exhaust Fluid Heater

The Dorman 904-386 Diesel Exhaust Fluid (DEF) Heater is engineered specifically for the BMW 335d to ensure optimal DEF system performance in cold conditions. This DEF heater maintains fluid temperature, preventing crystallization and ensuring proper emission control system operation.

• Designed for BMW 335d diesel models
• Inside diameter options: 112 mm and 115 mm for precise fit
• Includes two electrical connectors with male and female terminals
• Durable black plastic housing with a height of 133 mm
• Mounting hardware included for straightforward installation
• Female inlet and outlet fittings for secure hose connections
• Resistor-type level sensor integrated
• Wire colors: black, white, yellow, blue, red, and gray with plastic insulation

Detailed Product Description

The Dorman 904-386 DEF Heater is a specific-fit emission component designed to maintain the temperature of diesel exhaust fluid in BMW 335d vehicles. Its plastic housing is built to withstand under-hood conditions while providing reliable protection for the internal heating element. The heater features two electrical connectors with both male and female terminals, supporting three to four terminal configurations to ensure compatibility with the vehicle’s wiring harness. The heater’s inlet and outlet fittings are female type, facilitating secure connections to the DEF system hoses (hoses not included). The resistor-type level sensor helps monitor fluid levels accurately, contributing to the overall emission control system efficiency.

Applications and Problem Resolution

• Prevents DEF crystallization and freezing in cold weather
• Ensures consistent DEF flow to the selective catalytic reduction (SCR) system
• Helps maintain emission compliance by supporting proper DEF dosing
• Reduces risk of DEF system faults and warning lights
• Supports reliable engine performance in low-temperature environments

Installation Notes and Tips

The Dorman 904-386 DEF Heater comes with mounting hardware to simplify installation on the BMW 335d. Ensure the electrical connectors are properly matched to the vehicle’s wiring harness, noting the male and female terminal configurations. Verify the inside diameter (112 mm or 115 mm) matches your existing DEF line for a secure fit. Since hoses are not included, inspect existing DEF hoses for wear or damage and replace if necessary. Follow all manufacturer torque specifications and safety precautions during installation.

Quality Assurance and Warranty

Dorman parts are manufactured to meet or exceed OEM standards for fit, form, and function. The 904-386 DEF Heater undergoes rigorous quality control to ensure durability and reliable operation within the BMW 335d emission system. This part is backed by Dorman’s limited warranty, providing coverage against defects in material and workmanship under normal use.