Before the start of the heating season, auxiliary coolant heaters should be inspected for proper functioning and possible tuneup according to the manufacturer's instructions. Depending on the frequency of operation through warm months of the year, the auxiliary heater's condition can vary. Webasto recommends running auxiliary heaters a minimum of 10 minutes at least once a month during the non-heating season. This preventive maintenance prolongs the life and efficiency of the auxiliary heater. If at anytime instructions are unclear or you feel uncomfortable about procedures listed in this article, or have questions about the documentation received with the auxiliary heater, contact the manufacturer's authorized specialists. Keep the manufacturer's servicing manuals close at hand for information about inspection, diagnostics and repairs. You will also need the reference information provided along with the proper tools and test equipment suggested by the auxiliary heater manufacturer.

First, a visual inspection
The following is a suggested list of items that should be inspected at least annually and preferably before the heating season begins:

• Mounting — Inspect mounting hardware for looseness or missing items. Remove any accumulated clutter or debris from around the heater area, especially the area of the air intake and exhaust outlet.

• Exhaust system — Check the exhaust tubing for cracks, blockages, missing sections and loose clamps. Repair problems uncovered during exhaust system inspection.

• Electrical system — Repair corroded or damaged wiring and connections, inspect fuses and switches, clean battery connections and check the condition of the vehicle's batteries. Coat connections with an anti-corrosive compound.

• Fuel system — Inspect the system for leaking or damaged fuel lines, clamps and connections. Check for proper routing and secure the attachment to the vehicle along their total run. Replace the fuel filter and repair problems uncovered during the inspection.

• Coolant system — Inspect the system for leaking or damaged coolant lines, clamps and connections. Check for proper routing and secure the attachment to the vehicle. Inspect the coolant circulation pump for damage or seal leakage. Repair problems uncovered during coolant system inspection.

  Then, an operational test
  After you have completed the visual inspection and made all the repairs required, run the auxiliary heater to further diagnose its present condition. Before running the heater, make sure any coolant valves that may have been closed during the warmer months are open. Depending on the manufacturer of the auxiliary heater, you may be advised to perform a tuneup of the unit. This may including checking and adjusting certain internal items such as fuel pump pressure. Replacing fuel nozzles and cleaning carbon deposits out of the combustion chamber may also be required. These procedures are covered in the service manual for your particular auxiliary heater.

  Author Ronald W. Cowell is a technical instructor at Webasto Thermosystems in Lapeer, Mich.