hehe, i had this problem with my EL, turned out the engine was over heating due to busted radiator hose and empty reserve, car decided to not give me any hot air as it was too hot already all good now

I have an EA S1 GL CPEFI and my heater REFUSES to get hot it wont even get warm its just had the whole cooling system Flushed out (with solution) and has an AU type thermostat it runs cool on the temp gauge sits just below the Normal (Fairmont/S Pack cluster) my mates EA sits lower on the gauge and his Heater does work

I got my EF Fairmont at the end of April and went through winter driving with gloves on. I replaced the thermostat first and finally ran the diagnostics last week and noticed that hot air only came out with the "mode" on "feet", and switched to cold as soon as I changed to the other vents. Well summer is returning in South Africa and I now know how the heater operates!!

Found out my heater does work around 5am today coming back from Toowoomba (car ran like a champ, what a comfortable cruisers). God I needed it, what the hell is with Toowoomba and cold?! lol.