Drivers side heating not working after changing numerous parts

[Ashleighs1304]

So I have a seat Leon FR 2013 plate.. originally the car heating was freezing cold so replaced numerous parts including water pump, thermostat, heater matrix, new expansion tank etc and the pipes were still cold and only then the passenger side heating got warm but not red hot and the drivers side freezing cold still.
The pipes have been flushed and even an experienced mechanic is struggling with it as the heating is still mild warm on the passenger side and nothing on the drivers even after replacing all the parts. Can anyone help at all as I’m getting really frustrated with it now! Thank you

 

[SuperV8]

So I have a seat Leon FR 2013 plate.. originally the car heating was freezing cold so replaced numerous parts including water pump, thermostat, heater matrix, new expansion tank etc and the pipes were still cold and only then the passenger side heating got warm but not red hot and the drivers side freezing cold still.
The pipes have been flushed and even an experienced mechanic is struggling with it as the heating is still mild warm on the passenger side and nothing on the drivers even after replacing all the parts. Can anyone help at all as I’m getting really frustrated with it now! Thank you

Probably best to post in the mk3 forum - rather than the general one.

Leon Mk3 (2012-2020)

Third Generation Leon 5 door, SC (Sport Coupé) and the ST (Sport Touring)

www.seatcupra.net

What engine is it?
When the engine is hot (I presume the temp gauge on the dash goes up to 90?) - feel the small flow and return pipes which go to your heater matrix. Do they get hot? They should be, the flow should be a little hotter than the return, which shows the heater matrix is working and taking some heat out of the coolant.

If they are not hot the problem is in the engine bay - probably air?

If they are both hot - then the problem is probably your air distribution - flaps? You have several stepper motors which control flaps under your dash - one is for temperature and directs air over either the heater matrix or the AC evaporator. You can carry out a re-set/calibration procedure for these flaps - if this doesn't work they maybe seized/broken?
If is good practice to cycle your heater controls every few weeks - so hot to cold, windscreen to feet etc.. to fully cycle these motors/flaps and keep them working and not seizing from being in one position.

If one pipe is hot and the other is cold - then you have no flow through the heater matrix which is probably a blockage in the matrix.