W163 Heating staying cold

[Ssnipples]

Does anyone know anything about the following

My w163 a few months back heating stopped blowing warm air despite a fully warmed engine. Before I had a chance to investigate it began working again until a few days ago. Any ideas why it would work intermittently?

Not sure if it's connected but my electric sunroof has also randomly stopped working for a second time. Are these connected someway as a fault?

Thanks in advance
Steve

 

[merc85]

Not sure if these have a duo valve or not, could also be a Partially blocked heater matrix perhaps.