Air conditioning will not switch to air conditioning and blows hot air

SOURCE: air condition/heater

sounds like the air-conditioning expansion valve is probably not working correctly here is a way you can fix your air conditioning:

1. 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.

1. Become familiar with the major components to auto air conditioning:
   
   
2. 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

1. 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.
2. 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.
3. 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).
4. 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.
5. 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.

SOURCE: Air Conditioning

Sounds like the hig head-pressure cut=out is kicking in and shutting down the compressor. This is probably caused by not enough air being moved across the condensor coil (in front of the radiator). Check and make sure all the engine cooling fan components are in place and functional (fan clutch, shrouding, belts tight) and also check the coil for obstructions (Bug accumulation, road debris, litter). Clean the coil and radiator as much as possible at a self-service car wash, see if that doesn't help.

This can also be caused by an overcharged system (too much Freon). Sometimes when these symptoms first appear, the knee-**** response is to add another can of Freon, only to make things worse. If this is the case, I would recommend a system evacuation and service, replacing the dryer/receiver and pulling a 28mm/hg vacuum on the system, and then refilling with the proper amount of Freon, and cleaning the evaporator coils as well. This can only legally be one by an HVAC Certified technician, to insure excess Freon is not released into the atmosphere.

Hope this helps you figure it out, and good luck!

-WB

SOURCE: ford ka heater blows hot air all the time

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.

SOURCE: 97 Ford Econoline air conditioning and vent settings blowing hot

I know from experience that if the coolant is to low ( not just the freon levels in the compresor but the antifreeze/coolant level as well) the AC system will not cool and will blow hot. Check the coolant Antifreeze and freon levels, even with the Coolant being a little low my 1998 Ford E150 Van will blow hot. After you have ruled out of these possibilities and the chance it is the thermostat most likely the problem is what Ford calls the "Flap" it controls the air flow through the vent system when you switch from Heat to AC. When the Flap is working it closes off one systems air flow so as to not interfere with the current climate selection.

SOURCE: My air conditioning blows hot air. Won't accept

Is the system low on Freon? If not, you most likely have a bad A/C compressor, or a bad low pressure switch.