MAINTENANCE MATTERS

Keep your cool with MCI AC tips

The dog days of August may seem a long way off, but when it comes to AC maintenance, they might as well be right around the corner. Now's the time to prepare your AC system to keep passengers cool and comfortable spring, summer, and well into fall. MCI's maintenance pros have put together a few tips to help make sure your MCI coaches are ready.

1. Check and clean all evaporator and parcel rack AC filters, and driver's filter. Use low-pressure air, and replace filter elements as needed.
2. Clean all coils, including evaporator, condenser, driver's, and parcel rack coils, using a low-pressure air gun. For evaporator and condenser coils, use a low-pressure water hose in the direction of the fins on the coils — use an up-and-down motion to avoid bending the coils.
3. Check evaporator, condenser, defroster and blower motor brushes and replace as needed. The brushes are located behind brush covers — see your Maintenance Manual, Section 16 for the proper procedure.
4. Check all wiring, connectors, and relay and relay bases for loose wires, corroded connectors and pins or burnt relay contacts on each relay in front and rear junction boxes — see Section 7 of your Maintenance Manual for the locations. For E4500 or J4500 coaches, check controller connections — see Section 16 of your Maintenance Manual.
5. Check and adjust the clutch air gap on the AC compressor clutch. For adjusting procedure, see Section 16 in your Maintenance Manual.
6. Check clutch coil resistance per your Maintenance Manual, Section16. Resistance should be 8-10 Ohms on all coaches with 05G compressors.
7. Change the compressor filter and oil in your AC compressor per maintenance levels in Section 10 of the Maintenance Manual, or see Section 16, Compressor Maintenance.
8. Check refrigerant charge. Make sure the level in the receiver tank is full — this should be done by qualified AC techs only. See Section 16 for proper level information.
9. Adjust superheat on the main expansion valve. This procedure, as detailed in Section 16 of the Maintenance Manual, should be done at least twice a year so the system will work properly all season long.
10. Clean return ducts. These are in the ramp in front of the coach on models MC5 to D4500, and in the rear of the coach on later models. Clean window vents as needed from front to rear — this will ensure better airflow at windows. Also clean the return-air temperature probe located three seats up from rear of coach on the driver's side, or on the curb side for E4500 and J4500.
11. Check condition of belts daily, looking for cracks or uneven wear.
12. Check compressor cradle and mounts on the right-side rear engine compartment for worn bushings or cracks in the cradle. Lube as needed.
13. Check belt tensioner and air pressure settings at air regulator (if air cylinder tensioner applies). This setting is in Section 16 of the Maintenance Manual. Also check turnbuckle-style belt tensioner for loose ends or worn mounting bolts. Adjust or replace as needed.
14. Check all AC hoses and fittings — see Section16 in your Maintenance Manual for the location — and check for any signs of oil or dirt on the fittings and lines.
15. Make sure you have stock on all spare parts just in case something does happen, i.e. spare belts, evaporator and condenser  motor brushes, filter dryers, expansion valves, spare relays and Freon R22 or R134, whichever applies to your system.

By doing these simple AC system checks, you should have a trouble-free AC season. For more information, please consult your MCI Maintenance Manual or call the MCI Technical Support Line at 800-241-2947.