Heat Hazard Sensor (GLC Wagon & 626)
- Turn ignition on. "Overheat Exh. System" warning light should glow. Start engine and warning light should go out. Remove passenger seat and fold back carpeting (scuff plate and floor mat on 626) to expose heat hazard sensor wiring. Disconnect sensor and use a jumper wire to jump terminals of wiring connector; warning lamp should glow.
- If warning lamp does not respond as outlined, remove and test sensor. Wrap sensor and a thermometer in aluminum foil (electrical connector must be exposed for access). Place sensor and thermometer (wrapped in aluminum foil) in container filled with oil, place a second thermometer in container of oil. See Fig 1. Connect a battery and test lamp to sensor connector as shown in Fig 1.
- Gradually heat oil. Test lamp should glow when temperature inside aluminum foil reaches 284-320°F (140-160°C). If sensor does not respond as outlined, replace heat hazard sensor.NOTE: Do not heat oil above 392°F (200°C).