Module 7

Machine Exercises

🔧 Hands-On Practice 🚜 Explore System Operation
Practical Training Exercises
Hands-on expiraments to practice and discover fundamentals of the Bobcat AC.
Observations
This is a template of the whiteboard used next to each machine during exercises — instructors and students record readings there, not on this page.
Observation Reading
Duct Temperature Lower Upper
Duct Air Flow Good Bad
MCC LED Solid     Flash
Clutch Engaged? Yes No
Pressures High-Side Low-Side
Cycle Time On Off
Compressor Temps Housing Suction Discharge
Condenser Temps Inlet Outlet
Evaporator Temps Inlet Outlet
Heater Core Inlet Outlet
Exercise 1: Verify Proper Operation

Test conditions: Install a gauge set and lower the cab if necessary. Start the machine and operate af half throttle. AC on full. Give it 5 minutes.

  • Document temps and feel the amount of air flow at the ducts. Compare upper to lower ducts.
  • Fill in your observations table
  • Compare readings to 8 times rule of thumb
Equipment needed: Manifold gauges, Thermometer, Stopwatch
Exercise 2: Refrigerant Charge

Test Conditions: Recycling machine installed. Adjust refrigerant charge as described below then operate the machine at half throttle, AC on full.

  • Recover the refrigerant and recharge with only 0.5lb. Operate machine and fill in your observations table
  • Does your machine have a refrigerant sight glass? Any bubbles?
  • Recover the refrigerant and recharge with 3lb. Operate machine and fill in your observations table
Equipment needed: AC recycling machine, Thermometer, Stopwatch
Exercise 3: Airflow Testing

Test Conditions: Gauge set installed. Operate the machine at half throttle, AC on full.

  • Block the Condencer with cardboard. Fill in your Observations Table
  • Move blockage to cab recirc filter - Fill in your Observations Table
  • Record your observations of the suction line. Is it cold, wet, or frozen?
Equipment needed: Thermometer, Bobcat machine, clean filters
Exercise 4: Electrical Diagnostics

Practice electrical troubleshooting on Bobcat AC systems.

  • Bypass compressor clutch using high-current test light
  • Bypass pressure switch function (cuts out below 28 psi / above 384 psi on high side)
  • Voltage drop power circuit to MCC
Equipment needed: Multimeter, test leads, High-current test light, wiring diagrams
Exercise 5: Heater Valve Leaking

A common failure. The AC is working correctly, however, the heater core is hot and the AC cannot overcome it. Turn the HVAC temperature control switch to medium. Install a gauge set. Start the machine and operate af half throttle. AC on full. Give it 5 minutes.

  • Measure the duct temperature and notice the air flow amount.
  • Install a gauge set. Note the compressor cycle times.
  • Feel the heater core inlet and outlet lines.
Equipment needed: Gauge set, Thermometer,
Exercise 6: Identify stuck TXV

Test conditions: Install gausge set, operate machine at half-throttle with AC on full.

  • Use a heat gun to warm the TXV. Fill in your observation table.
  • Use an ice cube to cool the TXV. Fill in your observation table.
Equipment needed: Gauge set, Heat gun, Ice cube.
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