sounds like the air-conditioning expansion valve is probably not working correctly here is a way you can fix your air conditioning:
Realize that auto AC is basically a refrigerator in a weird layout. It's designed to move heat from one place (the inside of your car) to some other place (the outdoors). While a complete discussion of every specific model and component is well outside the scope of this article, this should give you a start on figuring out what the problem might be and either fixing it yourself or talking intelligently to someone you can pay to fix it.
Become familiar with the major components to auto air conditioning:
the compressor, which compresses and circulates the refrigerant in the system
the refrigerant, (on modern cars, usually a substance called R-134a older cars have r-12 freon which is becoming increasingly more expensive and hard to find, and also requires a license to handle) which carries the heat
the condenser, which changes the phase of the refrigerant and expels heat removed from the car
the expansion valve (or orifice tube in some vehicles), which is somewhat of a nozzle and functions to similtaneously drop the pressure of the refrigerant liquid, meter its flow, and atomize it
the evaporator, which transfers heat to the refrigerant from the air blown across it, cooling your car
the receiver/dryer, which functions as a filter for the refrigerant/oil, removing moisture and other contaminants
Understand the air conditioning process: The compressor puts the refrigerant under pressure and sends it to the condensing coils. In your car, these coils are generally in front of the radiator. Compressing a gas makes it quite hot. In the condenser, this added heat and the heat the refrigerant picked up in the evaporator is expelled to the air flowing across it from outside the car. When the refrigerant is cooled to its saturation temperature, it will change phase from a gas back into a liquid (this gives off a bundle of heat known as the "latent heat of vaporization"). The liquid then passes through the expansion valve to the evaporator, the coils inside of your car, where it loses pressure that was added to it in the compressor. This causes some of the liquid to change to a low-pressure gas as it cools the remaining liquid. This two-phase mixture enters the evaporator, and the liquid portion of the refrigerant absorbs the heat from the air across the coil and evaporates. Your car's blower circulates air across the cold evaporator and into the interior. The refrigerant goes back through the cycle again and again.
Check to see if all the R-134a leaks out (meaning there's nothing in the loop to carry away heat). Leaks are easy to spot but not easy to fix without pulling things apart. Most auto-supply stores carry a fluorescent dye that can be added to the system to check for leaks, and it will have instructions for use on the can. If there's a bad enough leak, the system will have no pressure in it at all. Find one of the valve-stem-looking things and CAREFULLY (eye protection recommended) poke a pen in there to try to valve off pressure, and if there IS none, that's the problem.
Make sure the compressor is turning. Start the car, turn on the AC and look under the hood. The AC compressor is generally a pumplike thing off to one side with large rubber and steel hoses going to it. It will not have a filler cap on it, but will often have one or two things that look like the valve stems on a bike tire. The pulley on the front of the compressor exists as an outer pulley and an inner hub which turns when an electric clutch is engaged. If the AC is on and the blower is on, but the center of the pulley is not turning, then the compressor's clutch is not engaging. This could be a bad fuse, a wiring problem, a broken AC switch in your dash, or the system could be low on refrigerant (most systems have a low-pressure safety cutout that will disable the compressor if there isn't enough refrigerant in the system).
Look for other things that can go wrong: bad switches, bad fuses, broken wires, broken fan belt (preventing the pump from turning), or seal failure inside the compressor.
Feel for any cooling at all. If the system cools, but not much, it could just be low pressure, and you can top up the refrigerant. Most auto-supply stores will have a kit to refill a system, and it will come with instructions. Do not overfill! Adding more than the recommended amount of refrigerant will NOT improve performance but actually will decrease performance. In fact, the more expensive automated equipment found at nicer shops actually monitors cooling performance real-time as it adds refrigerant, and when the performance begins to decrease it removes refrigerant until the performance peaks again.
Sounds to me like your heater resistor may be bad do you have any speeds on the fan because typicly you will still have high when this fails if so you may want to check fuse for heater and relay hope this helps
Taurus does not use a heater control valve. It runs coolant thru the
heater core constantly. You may have a temp blend door actuator problem
or a plugged up heater core is also very common. Feel the heater hoses,
they should both be very hot, it one is much cooler; you can try to
back flush the core.
Your problem is a faulty heater control valve. The design used on these vehicles allows for hot water to flow constantly and compete with the evaporator as there is no blender door. You have to replace the valve and possibly the control head. Meanwhile, you can bypass the valve to have cold air
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The most common cause of this is that you have a stuck air temperature control blend door, this can be a motor actuator issue or a jammed door or both (common). To replace both parts you will need to completely remove the dash from the car to access the blend door.
www.tahoeforum.com > ... > Technical Discussions Dec 5, 2008 - 10 posts - 7 authors
2001 Tahoe, the front heater blows a little hot air when the car warms up and then blows cold air. The rear heat seems to work fine. I changed ...
1.)If your System is OVERCHARGED this Will Occure due to the EVAPERATOR FREEZING UP
2.) Also if your HVAC Control Modual is Malfunctioning this will Aslo Cause this Condition, It Controls the BLEND DOORS that OPEN for COLD or HOT AIR Look Into these Items and Also Look Into wethrt the A/C Compressor Cycles OFF when it GETS OFF this Will POINT at the HVAC CONTROLER if it Cycles Off When Set For A/C or COLD Air
This is just an idea, but if the a/c is working good, it may be the relay that changes your heater from hot to cold....give it a shot..just an idea....Please leave a good ratin, it is very important to me...