Teego
MB Enthusiast
A few day ago I lost all cabin heating.
Fan, flaps, aircon and coolant level all good.
So, as you do, I trawled the net. The problem was the duo valve which would not open to pass hot "water" to the heater. This is a common problem.
The valve is not too expensive but it sits under the brake fluid reservoir (on RHD cars) and is a pig to get at.
Long story short, this is what I did:
1. Warm the engine to normal temperature
2. Select Hi on the heater controls with aircon off.
3. Locate the duo valve with a torch
4. With a length of softwood tap the valve repeatedly. I didn't use a hammer or any violence as the valve is plastic.
5. I then alternated between Hi and Lo several times as quickly as I could. Still blowing cold.
6. With the setting on Hi I turned the engine off and tapped the valve again several times - firmly but not enough to damage it
7. With the engine still off to relieve any "water" pressure on the valve, and ignition on I toggled several times between Hi and Lo.
8. Not hoping for much, I restarted the engine and set the heater to Hi - hot air flowed.
9. To test that all was well, I took a 10 mile drive
10. SORTED
Fan, flaps, aircon and coolant level all good.
So, as you do, I trawled the net. The problem was the duo valve which would not open to pass hot "water" to the heater. This is a common problem.
The valve is not too expensive but it sits under the brake fluid reservoir (on RHD cars) and is a pig to get at.
Long story short, this is what I did:
1. Warm the engine to normal temperature
2. Select Hi on the heater controls with aircon off.
3. Locate the duo valve with a torch
4. With a length of softwood tap the valve repeatedly. I didn't use a hammer or any violence as the valve is plastic.
5. I then alternated between Hi and Lo several times as quickly as I could. Still blowing cold.
6. With the setting on Hi I turned the engine off and tapped the valve again several times - firmly but not enough to damage it
7. With the engine still off to relieve any "water" pressure on the valve, and ignition on I toggled several times between Hi and Lo.
8. Not hoping for much, I restarted the engine and set the heater to Hi - hot air flowed.
9. To test that all was well, I took a 10 mile drive
10. SORTED