Just flushed rad heater core and block because i had no heat. flushed the system filled with new antifreeze. my temp gauge will change from 150 to 210 I have heat then i dont

Right think the problem is the heater core is blocked with corrosion ,now remove the bottom hose from the rad and the heater hoses then flush every which way you can including through the heater core reversing direction then ,refit all the hoses fill with water only and see if heater works if so the remove the bottom hose again and drain ,then add a minium of 3 litres of antifreeze ,its a anti corrosion agent as well as antifreeze and without it the internal of the engine will corrode and the slurry will block the heater first then the radiator ,

Possibly plugged or inerporable heater core. Possibly heater core valve (this diverts hot air through your heater system) When you flushed the block, was there a lot of contaminant? 95% of the time, cold heat means thermostat. Also there are a lot of really cheap after market thermostats, you can buy one as low as $6.00. That being said, just because a thermo is new doesn't necessarily mean it opens/shuts when it should. You can look on You Tube on how to test one in your kitchen with boiling water,.

So three basic things affect interior heat temps. Thermostat, plugged heater core/.valve, and insufficient coolant or liquid to tranfser heat. If your interior coolant (engine temp) is working normally and your vehicle reaches operating tempature according to the needle, your thermosat is probably not the cause.

My bet is somehow, your heater core is plugged so that their is not enough "flow"

no, not special but you failed to stated engine, there are many engines.
and some are very tricky here, like 2.0L.
First state the symptoms,
your post states its overheating, then no heat. (why?)
old post. but others might
Ill post , overheating ,
Example if me, with overheat.
I see my dash gauge, show overheating and engine power drops and pings, then steam vents from the rad, cap?
Over heating (ill skip cab heater but on 2L this path blocked causes thermostat to go quite nuts. not posting engine, makes this hard.)
1: full of 50% AF (antifreeze)
2: new thermoSTAT they age and fail fast. so get a new one.
put STAT in with the wax slug down, and jiggle bleed pin forward.
get air out of system after filling, (RTM)
start car, and....
4: then using and IR pyro gun we then check that
the thermostat housing hits 170F min. but not too hot.
run motor till top rad hose gets too hot to touch 180f is normal.
I had to drive 10 miles, to get it up to 180F.
my car has the hotter, 195 STA,T so runs at 195f. (helps cooling)
USING the pyro gun , the top and bottom of each rad tube.
This tool is Amazing.... and saves burn hands.
if the bottom of any RAD tube is way less than the others?, that is
a clogged UP rad tube. solution is , NEW RAD.
Usually rad repairs, are more costly than new. IN USA.
The water pump must spin at full speed, belt tight.
The impeller or some suz, motors likes disappear. from electrolysis action. so not looking at the impeller is a FAILURE on the mechanic side.
if this car has 2.0 I-4 (4 banger) it has a coolant tube on the rear
of the STAT housing, this tube must flow coolant at all times.
if it dont, the thermostat , will go nuts.
nuts means, that insufficient flow passes the thermostat wax block
causing the thermostat to cycle in a wild and random way.
I dont like this design but is reality. If applicable.
post country, post engine type and state the symptoms.

My 2008 had the same problem. It turns out that the coolant system, if not filled properly will cause air to block the transfer heat in the heater core. This is what I did, and it worked, while your motor is cold, pop open the caps on your radiator and your overflow. Top off your radiator to the brim with antifreeze, put caps back on. Start and bring up to operating temp, (I just drove to the grocery store). This will work any vapor bubbles trapped to get flushed out, and then repeat. This can take 2 or 3 times. Easy fix.

Your heater core could be bad.

Yes. Is there a heat valve in the heater hose may not be opening. Next no heat valve disconnect both heater hoses crank engine and see where the water squirts out of engine thats where the inlet side of the heater Hook the garden hose to the other side and blow it out probably full of rust change antifreeze more often

The heater core could be clogged. If your antifreeze is orange , then it is Dexcool antifreeze which causes slime and sludge to build up in the cooling system. It can clog a heater core. My suggestion would be to drain and flush the entire cooling system with Prestone Super Flush. Put in a new thermostat while your at it. Refill the cooling system with a green antifreeze that is labeled compatible with aluminum engine parts and radiators.Do Not refill with Dexcool antifreeze.

its inside the heater box and need the whole dash taking out ,pull the two feed pipes off the heater and flush with a garden hose reversing direction of flow ,refill with antifreeze 100% neat ,then if still no joy put a piece of cardboard in front of rad to reduce the cold air flow through teh rad and engine compartment this should do the trick. dont beleave me watch ice road truckers and see what they do to their trucks to keep the temperature up .

try flushing cooling system could be a blocked heater core.if flushing doesnt work remove and replace heatercore.

double check the fluid level again, other option is a blocked heater core