Quality Control & Heater Output Function Test
WARNING: This page is about a different car, the 2000 Mercedes-Benz C43, 2000 Mercedes-Benz C280, 1999 Mercedes-Benz C43, and 1999 Mercedes-Benz C280. However, it is still accessible from the selected car via links, so may be relevant.
- Position a temperature probe at each defroster outlet. Verify vehicle interior temperature is less than 68°F (20°C). Verify outside air temperature is less than 59°F (15°C). Adjust blower speed to position No. 5. Close all windows, including sunroof. Drive vehicle at least 10 minutes. If outside air temperature is less than 32°F (0°C), a longer test drive may be necessary.
- Adjust selector wheels to Red range. Verify "EC" (economy) button light in A/C push button control module is on. Adjust air distribution knob to 12-o'clock position. Test duration must be more than 5 minutes with engine speed at 2000 RPM. Temperature probes must indicate more than 131°F (55°C). If temperature is within specification, system is operating properly. If temperature is not within specification, possible causes are engine coolant temperature, coolant circulation pump failure, deposits in engine cooling system (including heater core), or left/right water valves (duovalves) failure. Repair as necessary. For coolant circulation pump testing, see DTC B1416: COOLANT CIRCULATION PUMP in DIAGNOSTIC TESTS. For left/right water valves testing, see DTC B1417: LEFT-SIDE WATER (HEATER) VALVE or DTC B1418: RIGHT-SIDE WATER (HEATER) VALVE in DIAGNOSTIC TESTS.