Heater Performance Test
Engine coolant is delivered to the heater core through two heater hoses. With the engine idling at normal operating temperature, set the temperature control to the full hot position, the mode control to the floor position, and the blower motor control to the highest speed position. Using a test thermometer, check the temperature of the air being discharged at the HVAC housing floor outlets. Compare the test thermometer reading to the Heater Temperature Reference chart.
| Ambient Air Temperature | 16°C (60°F) |
21°C (70°F) |
26°C (80°F) |
32°C (90°F) |
|---|---|---|---|---|
| Minimum Heater System Air Outlet Temperature | 52°C (125°F) |
56°C (133°F) |
59°C (139°F) |
62°C (144°F) |
See COOLING SYSTEM if the heater outlet air temperature is below the minimum specification. Both of the heater hoses should be hot to the touch. The coolant return heater hose should be slightly cooler than the coolant supply heater hose. If the return hose is much cooler than the supply hose, locate and repair the engine coolant flow obstruction in the cooling system.