Functional Test/Check

Before beginning service of the heater and ventilation system, perform this functional test. To obtain accurate test results, the thermostat should be fully open.

1. Start engine and warm-up to normal operating temperature.
2. Touch the upper radiator hose. It should feel hot to the touch, indicating thermostat is open.
3. Set fresh/recirc lever to FRESH.
4. Set temperature control knob to full COLD.
5. Set blower speed to HI.
6. Systematically move the mode control knob through its various positions, noting what vents the air is being expelled from at each setting. In the bi-level mode, air should come from the I/P vents and from the floor; in the defroster mode, most of the air should be directed at the windshield, with some air directed at the floor vent, and so on.
7. Make sure that the points where the air is being directed correspond with the symbols above each mode control knob position. In addition, the air coming into the passenger compartment should be approximately the same temperature as the temperature outside the vehicle.
8. Set the temperature control knob to full HOT. The temperature of the air entering the passenger compartment should now be much warmer than the air outside the vehicle.
9. Systematically move the mode control knob through its various positions, noting what vents the air is being expelled from at each setting.
10. Move the blower speed control knob from HI gradually down to LOW. There should be a noticeable decrease in the forcefulness with which air is being expelled from the vents, and a decrease in blower noise at each successive setting.