heaters not hot

[306__xrdt]

You need to take out termostat when flushing.
If not flushing you can use a plastic bottle and fill it upp with coolant bleed the screws one near fuel filter and one near front window after that start engine with bottle and and lett it go for a while when you hear fan going then the coolant going round the engine.
You can do it with termostat on or off both should work, if nothing happens then the teromstat is not properly working.
Radiator could also be blocked with dirt/rust in channel.