June 22, 2017  
A/C Systems Operation Check with Estimated Performance Guidelines

  • Park the vehicle and set the engine speed at 1500 RPM.
  • Set the HVAC controls to MAX A/C, the blower at high speed and the temperature control dial to the coldest setting.
  • Chilled air should be discharged from the supply louvers in the cab. After 3-5 minutes of A/C operation, the louver air temperature should begin to drop. Higher heat and humidity conditions, especially when the coach is exposed to a prolonged sun load, may result in longer cool down time. (See chart below for details)
  • Air inlet/outlet temperature differentials are greatly affected by ambient temperature and relative humidity. In cool ambient conditions, smaller differentials may be seen. Air can only be chilled to a certain level, and then the A/C compressor will cycle off to prevent evaporator freeze-up. High humidity may also result in smaller differentials; a large amount of cooling capacity is required to dehumidify air, as well as cool it. (See chart below for details)

Estimated A/C Performance Guidelines


The following performance guidelines are based on test conditions outlined above. Variables such as engine speed, condenser airflow, sun load, blower motor speed, chassis voltage and system age or charge level will all affect A/C system performance.

Air Temperature (Deg F) Entering A/C Unit Inlet - Outlet Air Temperature Differential**
RECIRCULATED LOW HUMIDITY HIGH HUMIDITY
50 5-10 5-10
60 10-20 10-15
70 20-25 15-20
80 25-30 20-25
90 25-35 20-30
100 30-35 25-30
110 35-40 30-35

**The inlet /outlet air temperature differential is measured by using inlet air at the recirc air grille (typically in front of the passenger's foot area) and the outlet air nearest to the blower (typically passenger's left dash louver). Based on the above, if you feel your system is not operating correctly go to "Frequently Asked Questions" for service options.

Terms of Use
Terms of Use Evans Tempcon Home Page