My renault wouldnt blow out hot air, it was the thermostat gone and was just circulating cold water round the system. Stat replaced, all was good.

The only way I knew it was the stat though was because the engine never got to temp, unless I was in stationary traffic.

You can normally tell if the cable is not connected and you can hear it change over if u get your head in passenger footwell while turning it before you strip it out, isn't to hard too tho

mine did the same an it was just the cable had snapped of the adjuster at the back, took heater off an glued it, sorted it

Air lock in system or head gasket

mine did that and it was the head gasket

they are on really tight tho as i found out

also, not uncommon for the cable to unclip itself from the panel.....

mine did this, turned out there was an air lock in the system somewhere. Just unblocked itself somehow.

If your engine is defo hot and it still blows cold air pull the heater out and make sure the cable is connected to the adjuster,

can be a sign of head gasket problems, but doesn't necessarily mean it is.

Whats your temp gauge reading?

iv gt a corsa b and my heater only blows out cold air any idea why its not blowing out hot wen a put it on hot