The A/C/ evaporator, or evaporator core, works as a heat exchange within a vehicle's engine. Most vehicles only have one evaporator, but larger vehicles, such as an SUV or van, may have two. The evaporator is located inside the passenger compartment of the vehicle, often times buried deep within the instrument panel. Vehicles that have two evaporators generally have the second located towards the rear of the vehicle behind a side panel, or above the rear passenger seats. Understanding what an A/C evaporator does it crucial to knowing how and when to fix it. The A/C evaporator looks and functions similarly to a radiator. It is made of aluminum, and the main physical difference is that it is much thicker and smaller than a radiator. Evaporators consist of several internal flow paths with attached fins. Air passes freely through the fins just as it would in a radiator, but the tubes carry refrigerant instead of engine coolant. Older vehicles use Freon, or R-12 refrigerant, but after 1994, vehicles use HFC-134a, or R-134a.

The cold refrigerant enters the evaporator at the same time as warm air enters from the engine's blower fan. The refrigerant absorbs the heat from the warm air, and humidity condenses on the evaporator's cool surface. The condensation drips outside of the vehicle through tubes, and the refrigerant completes its path to the compressor. The A/C evaporator works like the heater core in the vehicle, only in reverse. Comparing the A/C Evaporator to the Heater Core The heater core in a vehicle transfers heat from the engine to the cabin, but the A/C evaporator works in a reverse manner, transferring warm air out of the vehicle, and then cooling it down and sending it back through. There are similarities in the two components, and each need a series of heating and cooling system components to work properly. Passenger side under the dash Absorb passenger compartment heat Distribute passenger compartment heat A blower fan interacts with both the A/C evaporator and the heater core to help perform their main function.

Leaks, malfunctioning system components, and many other issues can cause the A/C evaporator to stop working. A driver needs to know what to look for, and where to look when the cooling system stops working properly. The most common issue an A/C evaporator could have is a leak, but there are several reasons why a leak occurs. In most cases, a seam or weld has gone bad. Corrosion inside the evaporator causes an outside-in leak. This problem occurs when leaves or other organic material enter the evaporator case, usually through the air intake vents. The moist atmosphere within the evaporator decomposes organic material fast, and forms corrosive material that damages the evaporator. Whatever type of failure the evaporator endured, it needs to be replaced. There is no easy way, or effective way to fix the A/C evaporator. The A/C evaporator is not an expensive part, but due to the placement, it can be costly for labor fees to replace it. A leak causes the refrigerant to dissipate, and in turn, the air conditioning in the vehicle not to work.

There are several steps that need taken to replace the A/C evaporator: The new A/C evaporator core should be installed in the reversal order of removal. Car owners should ensure that refrigerant is added, that the plate is installed in the right direction, and the inside wall of the joints are clean. ratings of window ac unitsOwners should always replace O-rings with new ones coated with refrigerant, and replace joint caps.types of ac window units Many reliable sellers on eBay offer heating and cooling parts for your vehicle. air conditioning units for home pricesIf your air conditioning is not working in your vehicle, replace the A/C evaporator with a new one from a reliable seller. Convenient shipping options ensure the part you order makes it to your door fast, so you can get your vehicle repaired and back on the road.

Search for the A/C evaporator for your car or truck by entering the search terms in the top of any page. Location, price range, brand, and many other pre-defined filters for a more specific search can then filter the search results.A wave of shimmering, sauna-hot air hits your face and takes your breath away as you open the door and settle into the car. Too bad there wasn't a tree anywhere near this steamy, black asphalt parking lot. Who would think a car's interior could get this hot?You immediately thumb the a/c controls and wait patiently for relief. A brief moment of warm air from those vents turns the sweat beading on your forehead into crunchy little salt tattoos. Within seconds, the air begins to cool off, and so do you. Not a moment too soon.But before you clear the parking spot, before the air inside the car even approaches acceptable temperatures--there's a funny smell. It's sweet and acrid. The smell builds for a minute or two and then the fan slows and the cool breeze dwindles.

There's a brief sizzle from under the dash, followed by an even more acrid smell. Paradise by the dashboard vents is over. Your fan motor has died.Okay, not every fan motor dies in such a spectacular blaze of glory. The lives of these devices are unpredictable. Sometimes the motors just keep zipping along and lose steam gradually--until they just don't turn anymore. Or the fan may croak on the spot without warning. That's usually an indication of seized bearings. These motors generally don't use ball or needle bearings, they just glide on a simple bushing of oil-impregnated bronze. Dirt and corrosion can create so much friction inside that they'll gradually grind to a halt. So, our first step is to find out what, exactly, went wrong.Start by checking the fuse. The condition of the fuse really won't tell you what the problem is--but stay tuned.If it's blown, don't replace it now, because there's a good chance the new one may blow immediately too.Find the fan underneath the dashboard and spin it manually.

This process might involve temporarily removing a duct if you have a cabin air filter. If the fan spins readily, the problem is usually electrical. If it feels sticky, or has rough spots as you turn it, just go out and buy a new one right now. Get out the meter, or at least a test light. It's time to chase voltages.Basics FirstTwist the ignition key to accessory (ACC) mode and turn the fan switch to high. Back-probe the hot line into the fan, and you should see 12 volts in the system. While you're poking around, be sure both the hot and ground wires are still attached. It's not impossible for these wires to be knocked loose by the errant toe of a boot or a suicidal Barbie doll lurking on the floor.Check the schematic--a few vehicles switch from the ground side of the fan motor, not the high side. If so, there should be 12 volts to the motor full-time, regardless of the switch position, and you'll need to check voltage on the ground side. If you have no juice to the motor, it's time to find out why.

Fusable LinkSometimes the problem is not the motor itself. A fan constantly turning full-chat is noisy, and unnecessary a lot of the time. So most fan blower switches use a voltage-dropping resistor assembly to slow down that motor to a quieter speed. When this resistor dies, the fan will no longer work at certain speeds. The resistor was blown on our test car--we knew that for certain because the voltage was only meterable at the motor's hot terminal with the switch set to high. We replaced the resistor block before doing any further diagnosis. These resistors generate a lot of heat, so they're typically mounted inside the plenum, right in the path of airflow from the fan. When the fan is compromised, the resistor overheats. Consequently, it's not uncommon to see fried resistors accompanying fried blower motors. The resistor is usually inexpensive ($10 to $15) and easy to swap out. If the fan motor on my car was dead, I'd probably go ahead and change the resistor while I had my head under the dash.

With the switch on a lower setting and the motor disconnected, you'll still see a full 12 volts of system voltage at even the lowest setting. The voltage won't drop down to a lower level until the fan motor starts to draw current.Our spent motor was completely open electrically, and wouldn't load down the circuit at all, even after we replaced the resistor. If your motor has bad bushings and still turns, albeit slowly, it probably draws enough current to cook itself from the extra drag. This extra current, you would think, would blow the fuse too. Unfortunately, there is often enough headroom in a fuse's rating to let the motor melt before the fuse pops, if it blows at all. If your fan motor is killing fuses, uprating the fuse to a higher amperage is not, I repeat, not, an acceptable solution. There's the chance of damaging not only the motor and resistor with the excess current, but also the wiring in the harness and the blower-speed switch itself. Parts ChasingWe ordered a replacement blower from a website, and of course the wrong part showed up.

So we ordered another one, from a different vendor. Big surprise, Part II: It was the wrong motor, yet again.That precipitated a trip to the local auto-parts store. And as we've come to expect, the counterman was able to crack the code for our particular vehicle and come up with the right part overnight. Said part was inside an identical box, with an identical part number printed on it. If you have a very old or odd car, you may have less luck finding a source. A dealership should be able to get anything for most late-model cars; expect to pay through the nose. If you have an older vehicle, you may need to look to the restoration market. My first source is usually J.C. Whitney, or the back pages of Hemmings Motor News. Last resort: junkyard parts.If you must use an older, boneyard fan, clean and lubricate the bearings. The bearing on the fan end of the armature is accessible: Spin the armature shaft and hose it down with brake cleaner. Follow up with oil--a few drops of LPS 3 (my personal favorite) or even motor oil.

The other end of the armature is usually inaccessible. You can try to disassemble the motor, but I've used this trick successfully: Drill a 1/16-inch hole in the stamped-steel end cap.Put grease on the drill bit to catch any shavings. Inject a sparing amount of LPS 3 or oil into the hole. Then clean up the area with brake cleaner and seal the hole with silicone gasket sealer. Can't find even an old motor? Take the fried one to an electric motor shop. For a surprisingly small amount of money, most motors can be rebuilt. This procedure starts with disassembly and inspection of all the windings for internal shorts, opens or shorts to ground. If the windings look or test bad, they can be rewound with fresh, varnished copper wire. The shop will also true up the commutator on a lathe and undercut the copper contacts. Following that, it'll clean up and lube or replace the bushings, replace the brushes (which are usually a standard size) and button the whole thing up. Not every motor is rebuildable, but in desperate times I've pried open some crimped-shut motors that weren't designed to be repaired.

A Breath of Fresh AirOkay, you've sourced a new, used or rebuilt fan motor. If it's not a new one, I'd recommend a test run on your workbench before going through the trouble of installing it. You can either run jumpers from the car battery or just use a battery charger or other 12-volt source. You'll need 10 amps or so to run the motor at full speed. When the jumpers make the connection, the fan will spin merrily. And since every action has an equal and opposite reaction, the motor housing will spin counter to the fan's rotation. Don't let it spin right off the counter onto the floor. Don't ask me how I know this.Installation is the reverse of removal. Reinstall any cooling ducts, and keep the wiring harness away from the fan blades. If your old motor came with any sound insulation, replace that too. Don't use duct tape to hold the insulation back on--the extreme underdash temperatures will dry it out within months. If you must, glue the insulation back with RTV (room-temperature-vulcanizing) silicone gasket sealer.

RELATED STORIES* PLUS: Seven Summertime Auto Myths Debunked* JAY LENO'S GARAGE: 3D Printer Replaces Rusty Old Parts* DIY AUTO: How to Fix Squeaky Brakes* FOLLOW US: Popular Mechanics is Now on Twitter!* FRIEND US: Find PM on FacebookFinding the Problem 1.If both hot and ground wires are still attached to the motor's frame, back-probe the hot wire to the motor armature with the key on and the fan-speed switch set to high. You should see full battery voltage. 2. Standing on your head with your face in the footwell isn't much fun, but you'll need to remove the motor's attachment hardware. 3. We managed to sneak this dead motor out of the plenum without removing half the dashboard. Unfortunately, they're not all this easy. Some fan motors are removed from inside the engine compartment, which, counter­intuitively, isn't necessarily easier. 4. The new motor had to be snaked up into place past some serious roadblocks in the footwell and under the dash. Be sure not to damage the plastic fan.