Repairs to Bobcat Compact Excavator Cab Heat / Air Unit

[MikePhua]

When the heating or air-conditioning unit in a Bobcat compact excavator fails, it’s often not a massive overhaul—but getting access and executing the repair can become surprisingly tricky. The following is a detailed, original narrative (based in part on a real repair account) of common difficulties, repair steps, lessons learned, and advice for future maintainers.
Background of Bobcat Cab HVAC on Compact Excavators
Bobcat’s compact excavators (e.g. 335 G series) provide enclosed cabs with a combined heater/air-conditioning (HVAC) module to keep the operator comfortable in varied climates. This unit typically comprises:

• A blower motor / fan to circulate air
  
• A heater core (hot coolant passes through)
  
• An evaporator / A/C coil (for cooling)
  
• Ducting, flaps, control resistors or control valves
  
• Mounting brackets, hoses (coolant, refrigerant), wiring
  

Because of tight packaging in compact cabs, the HVAC module is often tucked under or behind the operator’s seat or cab floor. In the reported repair, the blower motor failed, necessitating removal of the HVAC cover and motor.
Challenges Encountered During Repair
In one documented case, the technician removed the seat easily, but then discovered multiple complications:

• A white bracket welded to the back of the cab (a seat mounting bracket) sat only about ¼ inch above the HVAC unit, blocking upward removal of the module’s top cover.
  
• The HVAC unit could not be moved forward sufficiently, because coolant and refrigerant hoses passed through a small rectangular opening in the floor plate, limiting clearance.
  
• The technician did not wish to discharge refrigerant (i.e. avoid evacuating the A/C) or drain the cooling system and remove heater hoses, which would add time, risk, and cost.
  

Thus, direct removal of the cover or module was blocked by the surrounding structure.
Creative Workaround Executed
Rather than fully disassembling plumbing systems, the technician opted for a modest structural modification:

1. Using a die grinder with a cutting wheel, he cut a notch in the floor plate beneath the hose opening. This notch allowed the HVAC unit to slide forward enough for the cover to clear its side flanges.
   
2. With the notch in place, the HVAC cover was removed, and the blower motor was replaced.
   
3. After completing the repair, the cut-out section in the floor plate was reinstalled by welding tabs onto it, drilling and tapping holes, and bolting it back in place—restoring structural integrity while accommodating the new access notch.
   

This approach avoided the labor and hazards of discharging refrigerant or draining coolant, offering a lower-cost, field-doable technique.
Notes, Warnings, and Considerations

• The technician cautioned that when cutting into the floor plate, one must proceed carefully—there may be hoses, wiring, or the fuel tank nearby. A slip could damage those components.
  
• He speculated on how a factory shop might do the job—perhaps removing hoses or discharging systems—but noted that doing the repair this way saved “a lot of green” (money).
  
• Another user observed that many Bobcat mini excavators may share similar HVAC packaging, so similar constraint problems may recur.
  
• Someone else mentioned that on their model, the seat bracket was bolted instead of welded, which made the removal easier. Another caution: in some cases one might have to evacuate the A/C system in order to fully remove the unit.
  

Broader Repair Issues in Bobcat Cab HVAC Systems
Beyond blower motor failure, compact excavator HVAC systems confront other common issues:

• Clogged or blocked drainage: The drain valves at the bottom of the HVAC cover (often "duckbill" style) can become clogged with dirt. If blocked, water accumulates and may freeze in coils or drip back inside the cab. A Bobcat dealer’s knowledge base emphasizes checking drain valves in HVAC troubleshooting.
  
• Faulty heater control valve / mixing valve: If the valve that regulates hot coolant flow (or blends hot/cold) fails, heating operation may not function. In Bobcat units, a heater control valve (e.g. part number 7499018 in some models) has been implicated in HVAC failures.
  
• Switch or electrical faults: A weak or failing switch in the cab can fail to activate the blower or compressor.
  
• Air filter / coil contamination: Dust, sand, debris may accumulate on evaporator or heater coils, reducing airflow or heat exchange efficiency.
  
• Compressor, refrigerant leaks, or refrigerant circuit blockages: Standard A/C issues like leaking O-rings, faulty expansion valves, or clogged lines may degrade cooling performance.
  

Best Practices for Repair and Maintenance
To reduce future headache and keep the HVAC system reliable:

• Before disassembling, survey the surrounding brackets and clearance to anticipate constraints.
  
• Maintain clean drain valves / drain paths to prevent water buildup and freezing.
  
• Use caution when cutting structural panels—protect adjacent hoses, wiring, or the fuel tank.
  
• After making any access notches or modifications, reinforce or patch with tabs, fasteners, or welds to preserve floor integrity.
  
• If replacing the blower motor or resistors, ensure correct specs and fitment to match airflow and current demands.
  
• Check the heater control valve, wiring, fuse, switches if heating does not work.
  
• Use compressed air or gentle cleaning to clear dust from coils (heater and evaporator).
  
• Monitor refrigerant pressure and system health annually to preempt leaks or performance drop.
  
• Keep backup parts (blowers, resistors, control valves) handy if working in remote locations.
  

Practical Anecdote
At a midwestern rental fleet yard, one compact excavator’s cab became stifling in summer; the blower died. The maintenance team attempted removal but were blocked by seat mounts and hose routes. Rather than scheduling full HVAC discharge, a technician cut a modest notch and slid the unit forward—same method as above—to access and replace the blower. They then welded and bolted back a patch. The repair took only half a day instead of days of disassembly. The machine returned to service in time for the busy season. Later, they adopted that repair method as standard in their workshop for similar machines.
Conclusion
Repairing the cab HVAC system on a Bobcat compact excavator often involves more spatial constraint than mechanical complexity. The blower motor is a common failure, but limited access behind seats, brackets, or tight hose routing can make removal frustrating. Creative, minimal modifications—like cutting a notch in the floor plate—can allow needed access without full system disassembly, provided care is taken to preserve structure and avoid collateral damage. Combined with maintenance of drains, control valves, filters, and electrical components, such approaches help keep compact-excavator HVAC systems working reliably through seasons.