This is the second part of the heater/aircon unit. It houses the aircon evaporator, thats the radiator thing you can see inside the box. The pipes you can see to the left of the first picture carry the aircon refrigerant.
The pipe you can see across the front of the evaporator in this next picture is actually a temperature sensor. I'll explain a bit more about this soon.
I pulled the unit apart and gave it a good clean out, you can see in this next pic just how clogged it was.
There are a few bits included in this box as shown below. This first one is called a thermistor. I am not sure exactly what this one does but it must add some sort of resistance as it has what is known as a 'heat sink' on the back of it. That's the finned aluminium piece you can see in the second pic below. When resistance is applied to an electrical current, heat builds up. The idea of the heat sink is that air passes over it to dissipate the heat that builds up. Cunningly this is mounted so that the heat sink protrudes into the aircon box, so it keeps the hot part away from passengers in the car and other components as well as being in the best possible place to keep cool.
As I say I am not sure exactly what it this one does but here is what it looks like inside. If anyone knows what it does let me know and I'll update it here.
This next one is a resistor. A similar kind of thing. It has a wire winding inside a ceramic block. The wire winding creates resistance and as such reduces power. This particular one I think is for managing the fan speed. Full power straight to the fan gives you high speed, but if you put the power through the resistor first it provides resistance and the fan goes slower. Again this resistance generates heat so the ceramic block gets very hot. You couldn't hold on to it. This one also protrudes into the aircon box to help it dissipate the heat.
The pic below is the inside of the box that the evaporator sits in. It is lined with an insulation material. If it didn't, when the box got cold, condensation would form on the outside of the box and passengers in the car would keep getting drips of water on their feet. With the insulation though the condensate forms on the inside of the box and runs out of a drain tube. This is where the big puddle of water comes from that you see under a car that has just had the aircon running. You can see the drain tube at the bottom left of the picture.
And here is the aircon evaporator unit all tidied up and reassembled.
And here it is reunited with the heater fan box.
Now if you want to know how aircon works keep reading.........
The video clip below explains quite well how aircon works. Unfortunately it is a home aircon unit but the principal is exactly the same. Before you click play let me explain the diagram below. The right side of this picture is the cold side (the equivalent of the evaporator/radiator you saw me clean out above, which of course is inside the car).
The tank like thing at the bottom in the centre of the diagram is the pump or compressor. In a car this is attached to the engine and is driven by the fanbelt. It takes quite a bit of energy to get this pump working which is why your car is less powerful and less economical when you drive with the aircon on.
The left side of the diagram is the equivalent of the aircon condenser. Its like a second radiator and is used to dissipate the heat that is generated when the compressor turns the aircon gas back into a liquid. In the video the guy is standing by a big box with a fan. This is the home equivalent of the aircon condensor/radiator. In your car it is a small radiator attached to the main radiator and it will usually have its own fan.
Any how take a look at the video.....when he shows you the box in the backyard think of the cars radiator. When he says "house" think "car" and it should all make sense.
Another part that is attached to the bottom of the aircon box I just tidied up, that I haven't shown you yet is this circuit board. It is what is referred to in the wiring diagrams as an amplifier. There are two of them on the aircon unit. You kinda get the idea now why there are so many wires!!!!
These amplifiers are central to the control of Climate aircon. So what about this climate air then? What is it?
Standard aircon you manage the temperature by turning the aircon off or on and the heater off and on. You can also choose where you want the air to come from....vents by your feet or demisters or on a hot day you may want it blowing from the face vents. You can also turn the fan speed up or down to suit.
Climate air manages all this for you though. It has many sensors that it takes readings from and uses the readings to make make an analysis and decisons about how to control the unit. You will remember the temperature one I showed you above? It measures the temp of the aircon evaporator. This is just one of many....in fact there are sensors for......
Temperature inside the car
Temperature outside
Temperature of the heater core
A solar sensor
Engine water temp sensor
And there are probably others I've forgotten
The Amplifiers (the circuit board things) use this info to assess what to do with....
Fan speed
The heater
The aircon and
The various vents
The end goal being to maintain the temperature the driver has set and also to try and make the settings comfortable. When its blowing heat it will usually direct this to your feet. When its cold it will use the face vents etc. In effect climate air is a set and forget system doing away with the need to fiddle with the knobs all the time, it does all that for you automatically so as your car cools down it reduces the aircon. If it gets cold it brings the heater into play and if it gets really hot again it will cut the heat and reintroduce the aircon. Lazy eh!!!
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