My heater blows hot for a couple minutes then turns cold. After turning it off for a few minutes and back on, it blows hot then goes cold again.

Souds like it's way low on coolant. The heater will blow cold air when the cooling system is so low that there is no water (coolant) running through the heater core. Then the thermostat opens, it trys to be normal but the system is low so it gets too hot in just a few minutes. If its that low, there must be a leak somwhere.

-Check heater control valve. (The one open and closed water)
it should move when turn to hot or cold. If it move or turn.
-Next disconnect the heater hoses (Two lines) and flush with garden water hose from both direction for couple minutes.

You should be good for winter.

mai

the blending door runs on vacume check your vac lines around the heater to make sure they are plugged in sounds like u turn it and it works for a bit until it loses vacume i believe the temp switch on the dash works off vac too so it might be your problem

Under the dash there are doors that open and close to give you hot or cold. Sounds like you have a vacuum leak in a hose or one of the vacuum motors that moves the door I would hook up a cheep hand held vacuum pump to each one and see if they hold vacuum also the one that opens the door that keeps the heat blowing is the one to look at if the door stays open and you have heat with the hand pump and you don.t have to keep pumping it the hose or farther back is leaking.

you say it will blow cold and hot air for only a few minutes. You don't say but I assume you mean will blow cold a few min. when turned on AC max , blow hot only a few min. when turned to heater hot. Assuming thats the situation and you say AC charged and shows good on the low side -you should charge the AC to a full charge on the low side will cause problems with the AC air compressor kicking on and off. I suggest while the engine is running and turned to AC cold max watch the AC air compressor clutch to see if it does indeed kick on and off if so charge completely. As far as the heater make certain you coolant is all the way to the top and the best way to do this is when engine is completely cold remove radiator cap and fill completely and completely close cap then fill overflow container just to the cold level. That should fix your problem.

Probably a stuck open thermostat or the thermostat is the wrong temp range for your vehicle.

I have written a tip on this.
You may have a couple of problems. I would first replace the thermostat, and make sure you have the proper coolant(ant-freeze) level.
Please let me know how it goes and if you need further help I am here.

first check to see that you coolant level is full, check it after the engine has cooled down,so there is no pressure in the system. otherwise you possibly have a head gasket in the early stage of failure

Have you checked the coolant level? If it's low, it will result in diminished heat, and could be the problem.

sounds like a vaccum diaphram may be leaking try listening for hissing noises under dash near the glove box,set blower to lowest setting\off if you can and still have a\c on.