It looks like you're new here. If you want to get involved, click one of these buttons! PT Cruiser Air Conditioning Questions/Problems hi my wife has a 2006 2.4 touring edition with 36.6 k miles on it and the AC knocked off today...i cant find any relays or anything in the fuse box that seem to have anything to do with the HVAC system except for a single 10amp fuse that is fine...fyi when i have the hood up and the ac on i dont even hear the compressor cutting in and out...i dont think that it is low on coolant because in my previous vehicle experience they would gradually become less and less effective until they quit cooling because of coolant loss....any help would be appreciated thanks guys and galsSee Also: PT Cruiser Electrical Problems Sign In or Register to comment.Written Written Written Why do we need cooling?The body core temperature is around 37°C and that of skin is 33.7°C but the body constantly converts chemical energy to heat. Hence to maintain this temperature we need to dump that heat in surrounding environment. 

Mechanism of heat rejection :Radiation : Q = constant * {(body temp in K)^4 - (surrounding temp in K)^4}Convection Q = h * Area of body *{(body temp) - (surrounding temp)}Evaporation Q = he * Area of body *{(body vapour pressure) - (surrounding vapour pressure)}   Out of which convection and evaporation play major role as temperature difference between the body and the surrounding is very small to carry out significant radiative heat transfer.  Convective heat transfer on the other hand plays important role. It actually moves heated air from your skin and replaces it with cool surrounding air. In natural convection this happens due to density difference between hot air and cold air.    Evaporative heat transfer takes place as water from the body evaporates through pores in skin and takes away the heat of evaporation. The driving force for this mechanism is vapour pressure of water in surrounding air. Why air circulation is important?Convective heat transfer coefficient "h" in the equation depends on the velocity of air.

Roughly it is related to velocity V as h=8*V^0.6. Evaporative mass transfer coefficient also varies roughly the same. Hence by increasing velocity of air around the body, we can dump more heat. This reduces the temperature difference required for heat transfer. Logically one can increase the set point of AC to higher temperature (27-28°C instead of 24-25°C) and still have same level of comfort. This will help AC to run the compressor for less amount of time.About the heat rejection from fan Fan motors are much more efficient compared to compressor. Efficiency of a typical 50 W fan motor is around 80-85% hence the heat loss is hardly 10 W, which is very small.(Human body dissipates 50 to 80 W even while sleeping)So practically there will not be load addition due the fan heat loss. But turning on fan will only work on living things only as it does not actually reduce the temperature. So turn it off while leaving that room. To conclude always use fan with AC as long as the room is occupied.