Frequently Asked Questions - Heater Craft 100H Series Installation And Owner's Manual

Frequently Asked Questions

Why does my heater cool down when I'm idling?
Open cooling system – The majority of applications have an open cooling system. This
means that there is no pressure in the system. The water pressure is created by the
engine's circulation pump. The engine must be at 1200 to 1500 rpm to create enough
pressure for the circulation pump to circulate water to the heater.
Location of the heater unit – In your automobile, the heater is located close behind and
below the engine. This allows optimum circulation. In your boat, the heater may be above
the level of the engine and may have a greater distance between the engine and heater
unit.
In-line circulation pump – If your engine is normally operated at low rpm's it may be
necessary to install an in-line circulation pump.
My Heater has multiple speeds but the fan switch is wired properly.
Check the wiring diagram to be sure that the switch is wired properly.
There are several factory installations that use an in dash switch. The switch may not have
enough positions to operate the fan motor on all speeds. This will not harm the fan motor.
Does it matter which way the hoses hook up to the heater core outlets?
No, it does not. The water/coolant will flow through the core in either direction.
I have luke warm air coming out of the heater.
The hot water pressure will increase with engine RPM. This means on some applications
the heater will cool down during periods of extended idling. If you operate your engine at
low engine RPM's, it may be necessary to install an in-line circulation pump
On an engine application it is necessary to increase the engine RPM to create effective
hot water flow. Shop testing will not always provide adequate water temperature or flow to
test the maximum air temperature output. Certain engine applications may require a water
test to achieve actual heater output.
Hose routing – Check the routing of the hoses between the engine and heater unit for any
kinks or restrictions.
In-line circulation pump – If your installation has more than 15 ft. of hose between the unit
and the engine or if the heater unit is mounted more than 18" above the level of the
engine, then it may be necessary to install an in-line circulation.
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