Cold Air from Heater


Asked by Nov 11, 2008 at 10:32 AM about the 1997 Mercury Grand Marquis 4 Dr LS Sedan

Question type: Maintenance & Repair

I replied to another post regarding this topic but wanted a new thread so maybe I could get a quick reply.

I have had my car in twice for this problem and it still isn't fixed.  I don't want to take it in again until I know more about the car itself so I can avoid getting another part replaced and still have the same aggravating problem.

I have a brand new control knob and rheostat (sp) and a new thermostat.  I think the problem is under the dash, it will blow hot then cold then hot again.  When it is hot it is REALLY hot, and when it is cold it is REALLY cold.  I end up driving with the air completely off except sometimes I need the defog on, so I have to use it stone cold.  

Can someone explain to me how heat gets from the engine to my ankles and toes, which is where I would like it to be?  Thank you.

3 Answers


hmm i used to have the same problem with my car, i would have to be driving for over 15min for it to stay hot. Heating your car is pretty simple basically when you run your engine the water pump in the car pushes antifreeze all throughout your engine to cool it down. So you have antifreeze constantly being flushed through your engine and you also have antifreeze in you radiator. The radiator is used to cool the fluid. The fluid goin through the engine is hot. So when the antifreeze is going on its route it passes through what is known as a heater core which is usually located at the rear of the engine under the passenger side dash. the fluid heats up the heater core which is made of metal. To get heat into your car there is a fan blower that blows air through that heater core and into the cabin of the car. the only other thing i could think of is maybe the heater core is partially clogged.

2 out of 2 people think this is helpful.

I would agree with billy. you could have a plugged heater core. you could also could have a problem with a mood door inside the dash. Inside most hvac units there are doors that control the were the air flows. the one that controls the temp. could be opening and closing when it is not suppose to and would cause you temp to change.

2 out of 2 people think this is helpful.

Keep in mind as well, that Ford makes use of a heater control valve under the hood that regulates the flow of coolant into the heater core from the radiator. Has the same basic concept as an EGR valve and if it went faulty, would give you the symptoms you are experiencing.

4 out of 4 people think this is helpful.

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