Heater fan will not work until the car warms up and then it will start to work.

What you describe is true for many home heaters, but maybe not true very often for cars. For most cars - especially older ones, the fan speed is independent of the engine temperature, and the heater will not "blow warm" until the engine has warmed up. There are also many new cars that let you set a temperature, and then automatically change the fan as appropriate. Those have many different behaviors, but in order for others to provide help I think it might be helpful if you said which model and year car you were asking about.

bleed cooling system, probably there is air trapped in the heater core preventing warm coolant to circulate into the heater core. try this
1 open radiator cap fill coolant and put heater in hi heat
2 start engine and wait until you see the coolant start to circulate
3 squeeze hose several times watching if coolant volume decrease
4 add more coolant and repeat 3 until coolant volume stays same or start overflowing.
5 check if heater giving off warm air or repeat 3 and 4 until warm air blows on heater.
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or find the coolant bleeder screw, do 1 and 2
open bleeder screw until coolant come out, do this several times until no air comes out when opening bleeder screw, fill coolant in radiator.

I believe the mazda protege has a separate thermoswitch to activate the radiator's fan. Perhaps the fan keeps blowing until the temperature is too low. Try replacing the fan thermoswitch. Just take care to put in tis place a thermoswitch of the same temperature range.

its VERY likely that your heater core is getting stopped up.

The heater in your car works by circulating hot water from the engine into a copper or aluminum pipe coiled up in the dashboard. The heater/airconditioner's fan blows across it and the hot air comes out of the vents. This is why the heater doesn't work right away when you first start the car. It usually won't work until the hot/cold needle in the gauges is starting to rise up.

If your mechanic recently replaced the thermostat, its possible that there is air in the system which will result in less antifreeze in the car than it should be. If this is not the case, the heater core is probably stopping up and will require expensive replacement if it cannot be flushed clean.

Check to make sure the car is full of antifreeze IN THE RADIATOR, AND THE OVERFLOW JUG. Please be very sure there is NO AIR in the cooling system as well.

Scott

Assuming they checked the controls under the dash and everything is working, lets try to bleed the air from the cooling system. An air lock in the heater core could stop it from getting warm. You will need a gallon of antifreeze and a jack to raise the car. Here we go: remove the radiator cap. Set the parking brake, transmission in park, block the rear wheels. Jack up the front of the car so that the radiator is higher than the engine. Start the engine and put the heater controls on the hottest setting but don not turn the heater on. With the engine running, look in the radiator, the coolant at this point should not be moving, or flowing through the radiator because the thermostat has not reached the temperature required for it to open. If the coolant is flowing at this time, then the thermostat is open and should be replaced. Let the engine warm up and watch the coolant level. When the thermostat opens up, the coolant level will drop, and you will be able to see the coolant flowing or moving in the radiator. Add enough antifreeze to fill the radiator ack up. The coolant level will probably drop again, Add more coolant as required. Repeat this process until the coolant level stabilizes and no longer drops while there is flow or movement of the coolant. Replace the radiator cap and lower the jack. Turn the heater on. If the problem was an air lock in the heater core, you should now have warm air blowing from the heater.. Something else to observe is the cooling fan for the radiator. If the electric cooling fan was running the whole time the engine was running, then the switch controlling the fan is bad. The fan should not come on until the radiator is hot. If it runs all the time, the coolant won't get hot enough for the heater to work. Let me know is this works.

hi from uk can i offer this advice ? when you start engine let it warm up a little then drive untill temp guage reads warm at least ? then when you put front screen defrost on only select screen and No 2 speed then as temp reaches normal screen will clear fully if you select full speed on heat blower to clear screen at first start it will not work because the coolant from engine passing thro the heater matrix/radiator will be rapidly cooled by fan of heater TRY IT? in years gone by it was common remedy if you were stuck in traffic and temp rose towards hot you could cool system down by putting heater on full heat and the fan on max this cooled the engines coolant as it passed thro the heater ?hope you understand how heater/fan should work for optimum efficiency my wife has owned 2 of these accents and never had heat/demist problems it is surprising how many people consider the demist/heater systems are poor on many cars not just hyundai hope this helps best wishes

First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced.
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is warm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest flushing the heater core.

no fan comes on when engine cold start up .but it will come on when you turn on air conditioning or defrost on .if engine idling a while when temp get 190 degree the fan will kick on.if over heating you got air in system .wait until cools check coolant add more .crank engine let it idle few. minutes when start warming up turn off engine wait a while before removing radiator cap so you wont get scald.add more coolant .crank it again starting warming up turn off engine wait a while .add coolant .keep doing this procedure until your coolant stop dropping off .if you do this more than 6 times you got a leak some where.check crank level for signs.if oil level higher than normal.if everything looking good.when engine cool make sure add coolant to over flow jug cold level mark.

It's very possible the fan motor has quit. The squealing noise is caused from motor bearing failure. As the bearings wear out or dry up the motor is harder to turn and require more current to run the motor. On lower speeds, the motor runs off a series of resistors that reduce the amount of voltage and current so the fan runs a lower speeds. If the bearings are worn, there is not enough voltage or current to turn the motor and that's probably the humming noise your hearing.
Good observation by the way.
Let me know.
regards,

this is normal, heat comes from your motor so it isnt hot enough until you start working the engine