Hi,
As the title says the heater is blowing cold air when I set it to the max temp. This isn't really an issue in our weather however I was changing the coolant today and doing a 10 min flush and it says to turn the heater on to flush the water out of the heater core.

So my question is will turning the heater on still be effective to flush the water out even though its like the air conditioner is on instead?

Only 3.5 litres of water came out so there was definitely still a litre or so still in there.

I couldn't find a definitive guide. What I did was drain the fluid from the plug down the bottom. Refill with water and radiator flush fluid. Once it cools down tomorrow I will drain it again and refill with G13 and distilled water. Is this the method or do I need to drain the water from the engine block somehow?