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Be cool with A/C maintenance

MCI offers recommended preventive maintenance inspection schedule

By William “Gator” Pryne
MCI Senior Technical Advisor

Pryne inspects the A/C system during an MCI Technical Tune Up Session at the MCI Training Center in Louisville earlier this year. Photo courtesy of MCI

Summer is fast approaching, that time of year when a great number of bus and coach operators throughout the country must deal with air conditioning (HVAC) systems working their hardest. This is the time to give the A/C all the attention it needs to ensure reliable, optimum performance on the hottest days. Do not wait until it is too late and costly. Preventative maintenance is the key.

MCI offers these steps ensure passengers and the driver remain cool and comfortable during the trip.

The PM process should include checks of the A/C compressor drive belt, compressor oil level and the system refrigerant level as part of each and every HVAC system inspection.

Leave the engine turned off to check the tension and the condition of the A/C compressor belt without the engine running, as well as the condition of the crankshaft pulley and clutch pulley.

The belt must ride high on the pulleys for best performance. Refer to the maintenance manual and the drive belt manufacturer specifications and guidelines for information on when and under what conditions to replace the belt.

While the engine and HVAC system is running, listen for abnormal noises from the compressor and the condenser and evaporator motors. Check the compressor oil level and the refrigerant level only after the HVAC system has operated for at least 20 minutes. Conduct weekly checks of the condenser and evaporator coils and evaporator filters for cleanliness to ensure A/C efficiency.

Do not allow road debris such as scrap paper and plastic to block the condenser core. Check and clean the interior ventilation system on a regular basis.

Inspect the area around the compressor crankshaft seal and the system refrigerant hoses regularly for oil residue, which may indicate a leak. If a leak is detected, the maintenance manual explains the steps to make the repair.

Check the refrigerant filter regularly for a temperature differential of more than 5 degrees across the filter inlet and outlet connections, indicating the filter drier is becoming restricted and needs replacing.

Inspect the evaporator and condenser motor bearings and brushes monthly, along with the A/C compressor mounting hardware and the HVAC component electrical harnesses. Look for discolored terminals and connectors that may indicate a loose or failing connection. Use a mechanics stethoscope or a similar ultrasonic listening device to detect bearing failures before the problem. BR

Posted by on May 1 2011. Filed under Motorcoaches. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

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