Complete repair guide for the Hymer Aktiv – Diesel Heater Glow Plug & Fuel Pump Service. Follow these steps to diagnose and fix the issue yourself.
Parts & Tools You’ll Need
- Webasto / Espar ceramic glow plug
- Diesel heater fuel dosing pump (12V)
- Inline diesel fuel filter
- Diesel heater LCD control panel
- Combustion chamber blower motor
- Intake & exhaust silencer kit
- Diesel fuel line silicone tubing (4mm)
- Digital multimeter (auto-ranging)
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Step-by-Step Repair Guide
Step 1: Diagnose Heater Issues and Safety Prep
Start by connecting your digital multimeter to the heater’s 12V power supply to verify voltage output, as low readings often indicate fuel pump or glow plug failure. Turn off the engine, disconnect the negative battery terminal, and allow the system to cool for at least 30 minutes before proceeding with any component removal.
Step 2: Access Fuel System and Remove Lines
Locate the diesel heater unit beneath your Hymer Aktiv’s kitchen area and carefully disconnect the fuel inlet line by loosening the compression fitting with an adjustable wrench. Place a small container underneath to catch any residual diesel, then disconnect the return line and note the routing for reinstallation.
Step 3: Replace Glow Plug and Fuel Pump
Unscrew the ceramic glow plug from the combustion chamber using a deep socket, then install the new Webasto or Espar glow plug with firm, even pressure to ensure a proper seal. Next, unbolt the fuel dosing pump (typically held by 2-3 fasteners), disconnect its electrical connector, and install the new 12V pump in reverse order.
Step 4: Install Inline Fuel Filter and Tubing
Cut the fuel lines at appropriate points and insert the new inline diesel fuel filter, ensuring the arrow marking points toward the heater unit for correct flow direction. Replace any cracked or hardened 4mm silicone tubing with fresh fuel line, using new hose clamps to secure all connections and prevent future leaks.
Step 5: Service Combustion Chamber and Blower
Remove the combustion chamber cover by unbolting the mounting brackets, then inspect and clean the interior with a soft brush to remove carbon buildup and debris. Check the combustion chamber blower motor for proper rotation by applying 12V directly; replace it if the motor doesn’t spin freely or shows signs of grinding.
Step 6: Check and Seal Intake Exhaust Silencers
Inspect both the intake and exhaust silencer components for cracks, corrosion, or disconnected joints, as these directly affect heater performance and cabin comfort. Apply diesel heater silencer sealant or replace the intake and exhaust silencer kit if you find visible damage or loose connections.
Step 7: Test System and Verify LCD Display
Reconnect the negative battery terminal and power on the LCD control panel to confirm it displays normally without error codes. Allow the heater to run for 10-15 minutes on low setting, listening for smooth combustion sounds and checking that warm air flows consistently through your Hymer Aktiv’s cabin vents.
Recommended Parts
| Part | Link |
|---|---|
| Webasto / Espar ceramic glow plug | View on Amazon |
| Diesel heater fuel dosing pump (12V) | View on Amazon |
| Inline diesel fuel filter | View on Amazon |
| Diesel heater LCD control panel | View on Amazon |
| Combustion chamber blower motor | View on Amazon |
| Intake & exhaust silencer kit | View on Amazon |
| Diesel fuel line silicone tubing (4mm) | View on Amazon |
| Digital multimeter (auto-ranging) | View on Amazon |