Many questions have been asked about the air conditioning system used in the 1993 and on Volvo. 1993 was the first year for the North American 850, as well as a change in refrigerant from R-12 to R-134a. The change was mandated by the Federal Government. When the refrigerant change occurred basic operation of the A/C system changed as well from a TXV (thermal expansion valve) to a CCOT (cycling clutch orifice tube). Below is a basic block diagram of the components, followed by a brief explanation of their operation.

         Lets start with the most talked about component, the Evaporator. The evaporator is located in the climate control box which takes up most of the space behind your dash board. The evaporator removes heat, dries the air, cleans the air and the core provides the space for the R-134a to vaporize. The Red arrow coming from the Condenser to the Evaporator will have high pressure liquid R-134a. Just before entering the evaporator the liquid will pass through an Orifice tube that will cause a drop in pressure, this pressure drop allows the R-134a to reach it's boiling point (-26.15C / -15.07F) and change to a vapor. The now cold evaporator will absorb the heat from the air being circulated over the fins by the Fan. Evaporator failure is usually from small pin holes that allow the refrigerant to leak out.

         Follow the blue line leaving the evaporator to the Accumulator. This line in the vehicle is normally cool and has condensation on it. The function of the accumulator is to receive vapor and any liquid refrigerant from the evaporator to prevent liquid from reaching the compressor. The accumulator contains desiccant to filter and remove moisture.

         Leaving the Accumulator the R-134a should be in the form of a gas. The inlet to the compressor is low pressure gas, after being compressed the output is high pressure gas. The high pressure gas is then routed to the Condenser.

         The condenser is mounted just in front of your radiator, if you bend down and look past the grill, you will be looking at the condenser. The purpose of the condenser is to cool the high pressure vapor causing it to change to a liquid. The high pressure liquid is now routed out of the condenser to the evaporator via the orifice tube which starts the cycle over.

         I mentioned earlier that the system is a CCOT, cycling clutch orifice tube, this is how the system pressure is kept within operating parameters. As the vapor leaves the evaporator there is a low pressure switch in the line that will open the electrical supply to the compressor clutch should the pressure drop too low. Very often the first sign that the system is malfunctioning is the rapid cycling of the compressor clutch because of a loss of refrigerant. Because of the equipment required to correctly maintain and repair the A/C system it is recommended that it be done by a Certified Technician. Volvo has a climate control manual that details how to diagnosis and make repairs should you be inclined. The manual can be ordered from Volvo Technical Literature 1-800-25-VOLVO http://www.kencook.com/vcna/volvo.html . By far the most costly repair to the A/C system is the replacement of the Evaporator. The entire dash has to be remove and many components in the engine compartment as well. Below is a photo of the "Kit" that is used when replacing the Evaporator.

         The "Kit" includes a new treated evaporator, various "O" rings, a new Accumulator, and a pollen filter and bracket. The system holds 1.6 Lb. of 134a. Below is a photo of just how intrusive the dash removal is, just to get to the Evaporator. You really don't want to try this at home.