5. If an air pocket develops in the heater core, coolant will not circulate through the core. Check the manufacturer's recommended air bleeding procedure. The technician may also be able to bleed the air from the system by using a coolant system pressure tester to lightly pressurize the coolant system. Loosen one of the clamps and hose at the heater core but do not remove the hose. Lightly pressurize the coolant system, allowing the trapped air to leave the system via the loosened hose. When coolant starts to leak from the heater core fitting, re- tighten the clamp.
6. The heater core may need to be flushed. At times the heater core may have a build-up of sediment, which interferes with its ability to be a heat exchange unit. Flush the core and re-test.
Remember, an 85 degrees to 100 degrees F increase from ambient temperature is the normal operating range of the heater. If the ambient temperature is zero degrees, then the expected duct temperature should be about 90 degrees F.
About Four Seasons
Four Seasons, a remanufacturer of automotive compressors, also manufactures and distributes a complete line of replacement climate control products for passenger cars, SUVs, trucks, and fleets. Standard Motor Products, the parent company of Four Seasons, also offers ignition, emission controls, wire and cable, electrical and fuel delivery components to the aftermarket industry. For more information, visit www.4s.com.