Mercedes-Benz W202 heater blows only hot air
Mercedes-Benz W202 heater blows only hot air even with the control on blue – what is the fault?
The most common causes are the two solenoid valves in the engine bay, which stick in the wrong position, or a faulty climate control panel. A blown fuse for the valves or a detached valve wiring connector also makes the air come out only hot.
How do I clean the Mercedes-Benz W202 "jay's egg" valves?
The valves are two grey towers in the engine bay near the bulkhead. They come off with Phillips screws. 1. Remove the valves; a spring may fall out. 2. Sand the brown gunk off with fine sandpaper. 3. Reassemble and test. If the fault remains, the cause is probably the panel.
How can I tell that the fault is in the climate control panel?
The valves click when the control is turned to cold but not to hot: then the control works. Flashing panel lights or missing control on one side point to a panel fault. The cause is often a loose connector or a broken solder joint on the circuit board. Measurement: in the coldest position the valve has roughly battery voltage, in the hottest zero.