It can be issue with faulty thermostat,thermostat stops working and causes such problem,Its not a costly part,you can try replacing thermostat.But if you have already tried replacing thermostat and still the problem is same,then other possibility can be plugged heater core.The core get clogged and causes such problems.Get the heater core flushed and see the results,.If still the problem is same,then the other possibility for this problem is Duel coolant heater control valve.This Valve is located on the passenger side , front of the engine compartment.Replacing this valve will help.
See the diagram below that shows the location of this valve.
For car AC related and Heater related solutions. You can refer the options mentioned below:---
Car AC Blows Warm Air ?
How to test AUTO AC pressure?
AUTO Air Conditioning Troubleshooting?
AUTO A/C COOLING PROBLEM?
Fixing refrigerant leak?
How to locate Car AC Refrigerant leak?
CAR AC INTERMITTENT COOLING?
What causes INTERMITTENT COOLING on Car AC system?
Car AC making Noise?
BAD ODOR ON CAR AIR CONDITIONER?
How to Recharge Car's Air Conditioner
http://repairhelpcenter.blogspot.com/2011/10/how-to-recharge-cars-air-conditioner.html
See the diagram below that shows the location of this valve.
Always buy branded auto parts,local non branded cheap auto parts don't give exact required results,they get overheated and burned out or don't last long.The cost for branded original auto parts are bit more,but you get required results and they last long.
This details will help.
Thanks.
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