E30 Zone

Hi. Need some help for my e30 325i (1989). I have noticed that over the last few months I have to turn the heater switch almost to max to get some decent heat. On half way or even 3/4 it's not that warm at all. Can someone help as to what's going on so I can sort out. Thanks

Are your pipes goin to the heater matrix hot when the engine is up to temp?

Could be that the thermostat is stuck open.

Thanks for the replies so far. Will check the pipes. I am assuming that I will have to take thermostat out to check? Might as well replace it if I do that.