my ef xr6 heater isnt working iv cleaned out the heater box coz it was full of crap and changed the heater tap but still no heat? plz help if anyone knows y

Either you are not getting vaume to the heater tap or the core is blocked.

could it also be a thermostat issue?

well i flushed it all and still nothing so could it me the thermostat? and with the vaccum i took the vaccum hose off and it had vaccum but i duuno how much its spose to have

flushing doesnt necessarily mean a working thermostat.

take the thermo housing off & remove the thermostat & personally test it with hot & cold water in a sink using the tap. it should open & close.

Are you getting warm air at least (even if its slightly warm)

My sis's heater only gets warm air at best while my other 2 falcons & 1 fairlane get nice n hot air.

I suspect a blocked core along with old worn out heater tap.

ahhk yer my heater tap was DEAD so i changed that how can i tell if the core is blocked is it worth just buying a new thermostat?

He has a new heater tap. If you have vaccum then it possibly is a blocked core or hose. Take of your heater hoses, I know it is a pain, and try flushing through with a hose, see how it flows.

iv done that too anything else u can think of

So it flows freely through the heater core?

...do XRs have Climate Control? If so, might be blend door motor has died. Check for codes on the CC unit. If you don't have CC, when you push the tab over to full heat, does it turn anything or is it smooth?

blend door? it turns as it had since iv had it just only a little bit of warm comes out

Does your engine actually reach proper operating temperature?Does the motor actually feel hot to touch,and what does your temperature guage actually sit on?Common problem on Ef Falcon for thermostat to stick in open position,thus not letting engine warm up fully, and causing heater to blow out warm air in hot position.As stated above,remove and test thermostat(a thermostat that is open when cold is obviously rooted), or even fit a new one as they are not that expensive(even from Ford) and pretty easy to fit.Also check that coolant actually flows through the metal heater bypass pipe as corrosion can easily restrict flow through this.
Another thing to consider is that you may have an air lock in the cooling system which may be restricting flow to the heater core.To fix this ,set heater control to hot,refill coolant to min mark on coolant recovery/header tank,remove radiator cap or loosen it half a turn and run engine at 2000 rpm for 10 minutes.Allow engine to cool and top up coolant to max mark on header tank.(if an air lock was present,the level should drop below the min mark after cooling.).