E200k Heater not working

[BobTheLark]

My E200k 2005 Saloon has an intermittent heater issue, most of the time it refuses to come on, the mechanic has flushed the system and is happy its not blocked but seems to think its electrical, I have looked at the fuses next to the steering, could it be a faulty relay or something

 

[Blobcat]

If it’s the fan not working then water ingress due to blocked scuttle/battery drains are common enough.
If it’s not getting hot then duo-valves can block up

 

[BobTheLark]

If it’s the fan not working then water ingress due to blocked scuttle/battery drains are common enough.
If it’s not getting hot then duo-valves can block up

The fan is working, its just blowing cold air, even when the thermostat is set to 25c+