Heat is blowing cold even at 90

Can you tell if the engine is heating up? May need a thermostat.

No the engine is not heating up. the temp gauge is almost to half

The temperature gauge being at half way is were it is suppose to be. sounds like you need a blend door actuator. This would adjust the temperature inside the car. Yours must be open.

can you please give an idea how much it will cost and where is located? thanks in advance

Ok, also what else may be wrong is there is a Temperature Sensing Electric Heater Valve which is in the heater hose. This item looks to be $30 to $35, The HVAC Heater Blend Door Actuator is like $35 to $40. This is somewhere under the dash.

thanks very much. If I don't fix it now will it cause a damage to anything? where is the Temperature sensing Electric heater valve

In the heater hose under the hood. No it is not hurting anything but your comfort.

how much you think is cost to replace the blend door actuator

Can I do it myself

Yes you can do these things your self. But you are going to want to do some checking so you are not replacing things you don't need. The Blend Door Actuator are around $30 to $35 and the Heater Valve is around $35 to $40. Check something first here, it is easy, get the car all warmed up go for a ride or something, then go under the hood and follow the heater hoses, you should find something installed in one of them (Heater Valve) and check with your hand to see if on the side closest to the heater core see if one of the hoses is cooler than the other, This would tell you if it is that Heater Valve.

ok thanks very much.