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:
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.