The Propex heaters were designed to be safe and reliable sources of heat for your vehicle. Being mounted in a non-stationary vehicle presents it's own challenges as the units are subject to vibration and exposure to all types of environments. Because of this, Propex designers err on the side of caution and create distinct operating parameters for the heating units. If the heater's electronic protection system senses that the unit is outside safe operating parameters it will show a fault code and shut down for inspection.

The three-flash code results from over- or under-voltage conditions. This is typically seen when the heater is installed into a vehicle with a solar charging system in addition to the standard alternator charging circuit. Solar charge controllers can allow a voltage spike at times of peak solar gain. The upper limit of the Propex electronics is around 15V before the heater sets a fault code to protect itself from over-voltage.

To ensure that the heater is not plagued by over-voltage conditions, we recommend either an inline 12V voltage regulator or an inline switch be installed on the 12V positive wire coming into the heater. A voltage regulator will modulate the current of the main electrical system and prevent damaging voltage spikes. Regulators can be found online for about $25.

The three-flash code can also be a result of undervoltage. Check that your battery is fully charged.

Learn to reset the fault codes.

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