The requested URL /vbb/showthread.php?1068621-Brand-new-central-AC-freezing-canNOT-find-cause was not found on this server.When summer’s here, or really any time you want cool, dry air while driving, your car’s air conditioner (AC) is critical to your comfort and safety. Unfortunately, frozen AC lines can put a major kink in your road trip. Why are your car AC lines freezing up, and what you can do about it? Usually, AC is one of those forgotten systems that you never really think about until it stops working. Sometimes there can be worn or unmodified AC systems that function for years without a problem. On the other hand, if your car has been in an accident, has ever had any AC components removed or had any service done, the situation is ripe for frozen AC lines. What Causes Car AC Lines to Freeze Up? Really, the only thing that should be in your car’s AC system is refrigerant and oil. To keep these things inside and others — such as air, moisture and dirt — out, the pipes, hoses and seals are specially designed to maintain a tight seal.

The problem of car AC lines freezing up is caused by moisture that has been introduced into the system. At the expansion valve or fixed orifice tube, depending on the system, liquid refrigerant instantly expands into a gas, forcing the temperature to drop. Moisture in the system can freeze at that point, blocking refrigerant flow through the valve, and you’ll notice you have warm air coming out of the vents. how to install a hvac unitAs the valve warms up again, the ice melts and refrigerant flows, so you’ll get cool air again, but the cycle will continue.rack mount ac unit Generally, the only way that moisture can get into the AC is if the system is opened up or if you have a leak. thru the wall air conditioner canadaIf there is a leak, air and moisture can be pulled in by vacuum on the low side of the system.

Also, any time that the AC system is opened, moisture can get in. For example, if you use an R-134a top-off bottle to fill it up, a little moisture can get in when you open the valve cap and install the can. Similarly, if an accident breaks the system, such as the condenser or one of the lines, the open system can freely absorb water from the air. Normally, the receiver-dryer absorbs some of this moisture, but it only has so much capacity before it is saturated, leaving the rest to float about in the refrigerant stream. What Can You Do About Moisture in the System? If you notice your car AC lines freezing up, you have to get rid of the moisture that’s causing it, starting with a full leak check. Recover the refrigerant from the system and make any necessary repairs to parts such as O-rings, hoses, lines or evaporators. If the system has been opened for more than a few hours from an accident, damage or corrosion, the receiver-dryer absolutely must be replaced. It can become saturated when left exposed to the air.

Alternatively, if the system has only been open a few minutes, during recovery and evacuation for engine repair, for example, you probably won’t have to replace it. Evacuate the AC system for about 30 minutes to boil off any moisture in the lines. Finally, recharge the system with the proper quantities of refrigerant, oil and a little ultraviolet dye for future leak detection. For more information on car AC systems, chat with a knowledgeable expert at your local NAPA AUTO PARTS store. Photo courtesy of Pic Basement. So You Left Your Convertible Top Down In The Rain: Don't Panic! How to Apply Touch Up Paint Like a Pro You know how when you change the filter in your air conditioner, it has a little arrow on the edge showing which way the air is supposed to flow through it? What do you think happens if you put it in with the arrow in the wrong direction? And then let it get too dirty? That's what happened with the filter below. Notice that it's dirty. Notice also that it seems to be a bit lighter in color in the center.

Looking at it from the side (above), you can see that the filter material is blown out. The blower in the air conditioner was trying really hard to pull air through the filter but the static pressure across it was high because of the dirt. Looking at the other side of the filter, you can see the wire mesh is now separated from the filter fabric. Of course, now it's clear why that wire mesh is there in the first place. It holds the filter fabric in place to keep it from getting sucked into the blower. What happened here is that the air conditioner pulled so hard on that filter that it sucked big chunks of the dirt and fabric off of the filter. Then it deposited them on the evaporator coil. A while back I wrote about a dirty evaporator coil, and that one had a large accumulation of small stuff. In either case, the result is that air can't move through the coil very well. The coil gets colder and colder because it's not picking up heat from the house. There's some water there because of the air that does get there.

Then the coil turns into a block of ice. The photo above is not from the house where I took those filter photos because I didn't open up the unit. It was definitely frozen up, though, because the ice was even coming out of the housing. The photo here does show what happens, and you can see that when a coil freezes up, no air will move through it. This picture is from one of my favorite Facebook pages, HVAC hacks and other screwups.) The Sludge That Kills — Post Mortem of an Air Conditioner heating & cooling distributionThere are a variety of things that can cause air conditioning freezing. The first thing to do is see if the indoor (evaporator-air handler) fan and compressor are both running at the same time, then turn the unit off and let all the ice melt. If the compressor is running and the evaporator fan isn't, you've already found the main cause of your air conditioning freezing problem. The indoor coil will freeze up if the compressor runs without the evaporator fan running.

Check to see if ice has built up enough to stop the fan. If it has, (and it's possible with wall mounted ductless mini split units and some window units), the fan may run normally once the ice melts, and the cause of your air conditioning freezing problem could be something else. If you are the equipment owner trying to take care of this air conditioning freezing problem yourself, and you get to the point that you have to call in a technician, it could save him time, (which saves you money) if you have already verified whether the evaporator fan was or wasn't running with the compressor, and if ice had built up enough to stop the fan. Once the ice has melted, check the fan or blower blades, and see if they're clean and not obstructed by something like a plastic bag, other debris, or mould growth. Remove any obstructions, and if necessary, remove the blower and clean it. Before tearing into the rest of the unit, check the thermostat and make sure it's working right.

Do the cool contacts open when the t-stat is turned up to a higher temp than the room temp? If not, the thermostat has failed, and never turns the unit off, which can definitely cause an air conditioning freezing problem. Do the fan contacts open and close when the thermostat setting is turned higher and lower than the room temperature? If the fan contacts never close but the cool contacts do, the thermostat has failed and caused your air conditioning freezing problem. If the fan contacts close, but the fan doesn't run, check the fan relay in the air handler. If the fan relay is not getting control voltage, the circuit is open between the thermostat and the fan relay. Look for a loose connection, wrong connection, dis-connection, or broken wire. If it gets control voltage but doesn't energize, it has failed, and must be replaced. If it energizes but the fan doesn't run, check for line voltage on the load side of the relay. If there is line voltage on the load side of the relay and the fan doesn't run, you'll have to troubleshoot the load side circuit and the fan motor as detailed further on.

If the thermostat checks out ok, set the thermostat to "fan on" and make sure the blower runs in the correct direction and at the proper RPM, that it is installed in the housing correctly, and is the right size. If the blower is installed backwards or is running in reverse, the coil can freeze up. (Although I have seen several units that didn't freeze up with reversed blowers.) You will need to turn the blower around, reverse the rotation of the motor if it is a reversible rotation motor, or install a motor with the correct rotation. A blower that runs too slow can cause an air conditioning freezing problem. You'll need to install a motor that runs at the correct speed. A blower that is too small, or that is installed in the housing incorrectly, can cause an air conditioning freezing problem. You will need to install the correct size blower, and be sure it is installed correctly in the housing. This means centered, with volutes installed, and the curve of the vanes matching the outlet of the housing.

If the blower motor is the wrong size, if the bearings are failing, or if it has an open start winding or a failed run capacitor, it could be overheating and stopping intermittently. A motor that is overheating and stopping intermittently can cause an air conditioning freezing problem. To check out the evaporator fan motor: Check the resistance readings of the motor windings. If you get a readable resistance between all three windings, the motor windings should be ok.If it turns free and easy, the bearings should be ok. If the shaft is hard to turn, lube the bearings with 20 SAE electric motor oil if there are lube ports. If that frees the shaft, it should run ok for a while, but the bearings or bushings may be deteriorated to the point that they'll sieze again soon. If the shaft doesn't free up, replace the motor. If the shaft turns freely, check the capacitor. The best way to check the capacitor is to replace it with a new one of the correct rating.

If the motor runs, close the air handler panels, and take an amp draw on the motor. If it's normal it should run OK, and if the motor was the problem, your air conditioning freezing problem should stop. Ok, if you've verified that the controls and fan are good, take a break for a diet soda, and then we'll see if the evaporator coil or ducting are the cause of your air conditioning freezing problem. Take a look at the evaporator coil.Can you see your flashlight shining through from the other side? If the coil's dirty, you'll have to do some air conditioning coil cleaning. If your air conditioner is a window type, our page about how to clean window air conditioners has some pointers you might find useful. A dirty evaporator coil is a common cause of air conditioning freezing, And it's one of the problems that can be prevented with regularly scheduled If the coil is clean, check the ducting to make sure nothing is blocking air flow.

Blocked ducting will stop air flow through the evaporator coil, and this will cause the coil to freeze up. If your coil is clean and the ducting is clear, let's run the unit and check the operating pressures and temperatures. If your discharge and suction pressures are low, with a low compressor amp draw, low subcooling, high superheat, and low temperature splits accross your evaporator and condenser coils, you probably have a leak. Shut the unit down, find the leak and repair it. Once the leak is found and/or repaired and you're ready to run the unit, our Charging Air Conditioning Systems page offers some tips that you might find helpful. If you are totally unable to locate the leak with a bubble solution or electronic detector, you'll have to charge in refrigerant to correct pressures, temperatures, and superheat and subcooling values, and it would be a good idea to add some air conditioning leak detector dye so the leak can be found later on.

You have to use some common sense about leaks. If the leak is so small that you can't find oil or any other sign; unless the customer agrees to pay you for all the time you spend, it's more cost effective to charge in the small amount of refrigerant it will take to get the unit running correctly, finish the service call, and be on your way. I can't imagine that there's a service technician out there who hasn't run into the same problem many times. Use some common sense, be up front with your customer, and if you've done your best not only to find the leak, but to get the unit running right and save your customer unnecessary expense, consider it a job well done. If your suction pressure is low enough to cause the evaporator to freeze up, but you have high subooling and high superheat, either your metering device is restricted or the wrong size, your drier is restricted, or your liquid line is restricted. Evaluate all of the system's operating characteristics to isolate the restriction.