For immediate repairs, locate the impeller housing assembly (part #M143965). This critical section withstands 5,800 RPM during operation–inspect the blades for nicks exceeding 1.5mm, as damage reduces efficiency by 18%. Replace the housing if cracks appear near bolt holes; torque to 35 ft-lbs with yellow thread locker.
Refer to section 5B of the official schematic for the auger drive system. The 1/2-inch shear pins (#M108172) are engineered to fail at 450 ft-lbs of impact–always keep spares. Misalignment here causes premature belt wear (#M143889), which should measure 1/16-inch deflection under 10 lbs of pressure. Verify sprocket teeth count: 12T input, 42T output.
Lubricate the gearbox (component #M147724) biannually with 80W-90 gear oil–fill to the lower sight glass mark. Overfilling increases operating temps by 12°F and voids warranty. For the chute rotation mechanism (#M143907), adjust the 3/8-inch hex bolt clockwise until resistance increases; excessive force strips internal nylon gears.
Troubleshoot discharge chute clogs by removing the clean-out cap (#M143921). Use a 3/4-inch rod to clear frozen debris; never strike with metal tools–this bends the aluminum housing. For electrical issues, check the engine control module (#M139447) voltage: 12.6V at rest, ≥10.5V during cranking. Replace spark plug (#CJ-8, .030 gap) every 50 hours.
Order parts using exact OEM numbers–aftermarket alternatives vary ±3% in tooth pitch, causing chain slippage. Store components at 40-50% humidity; rubber seals (#M143936) dry-rot if exposed to sunlight. For assembly, follow annotated diagrams showing clockwise torque sequences: flange bolts (7/16-inch, 45 ft-lbs), bearing caps (1/2-inch, 55 ft-lbs).
Model 42 Rotary Clearing Equipment Component Guide
Identify the impeller housing immediately–its stainless steel construction requires annual inspection for hairline cracks near bolt holes, especially after extended operation at temperatures below -15°C. Replace only with OEM torque specifications (18-22 Nm); over-tightening distorts the mounting flange, causing premature bearing failure on the discharge chute pivot.
Check the traction drive belt tension every 25 hours of operation using a straightedge gauge: deflection should measure 12mm under 4kg pressure at the midpoint. The belt’s Kevlar cords degrade unevenly if exposed to oil residues; wipe with isopropyl alcohol weekly before storage. When replacing, route the new belt over the secondary idler pulley first, then the primary drive sheave to prevent misalignment that causes slippage.
Lubricate the auger shaft bearings with lithium-based grease (NLGI #2) through the zerk fitting accessible behind the chute rotation gearbox–this prevents seizing in subzero conditions. Apply 3-4 full pumps until grease extrudes from the shaft seals; excess indicates clogged passages requiring disassembly and cleaning. The gearbox itself uses 80W-90 synthetic gear oil, changed every 100 hours; overfilling causes churning foaming that reduces chute rotation torque by 30%.
Inspect shear pins after every heavy freeze-thaw cycle. Use only grade-5 alloy pins with precise diameter (6.35mm); common steel wire substitutes bend unpredictably under load. Install a secondary electrical kill switch wired in series with the engine cut-off for emergency auger shutdown–this prevents overspeed damage when clearing dense slush at minimum engine RPM (2400).
Locating Authentic Schematics for the Model 42 Blower
Start with the manufacturer’s official support portal at parts.deere.com. Enter the exact equipment identifier–look for a metal plate on the machine’s frame showing serial number PC47420 or a nearby variant. The site filters results instantly, displaying interactive exploded views grouped by assembly.
Dealerships stock printed catalogs under part number PC9998 for this series. Call ahead before visiting–some locations store these in backroom archives rather than sales floors. Technicians often keep PDF backups on tablets; politely request a shared file if online access is unavailable.
Third-party agricultural databases like Partstree and Jack’s Small Engines host mirrored schematics. Verify compatibility by cross-referencing OEM references: the auger housing appears as M142706 in all listings. Discrepancies indicate outdated diagrams.
eBay sellers occasionally list original service manuals as “lot” items. Sort by “Ending soonest” and filter for sellers with 98%+ positive ratings. Manuals often include fold-out schematics not found digitally.
Local libraries in rural areas frequently carry equipment repair periodicals from publishers like Haynes or Primedia. Request “snow removal maintenance” in the catalog–these often contain detailed line drawings for older model variants.
User forums such as TractorByNet and GreenTractorTalk have dedicated threads cataloging uncommon schematics. Search using “42 series impeller breakdown”–seasoned contributors attach high-resolution scans of dealer-only documents.
Manufacturing reps sometimes share internal documents during warranty claims. Present a clear issue description–for example, “shear pin failure in discharge chute”–and ask for related visuals. Reps may email a subset of the official diagram.
Check salvage yards specializing in compact outdoor power units. Operators often dismantle equipment on-site and will photograph assemblies if you provide specific component names (e.g., “auger gearbox housing”). Ask for shots taken under bright light to capture embossed part codes.
Critical Elements in the ST42 Model Blower Assembly Guide
Replace impeller blades every 200 operating hours under heavy use or annually in moderate conditions. Original equipment manufacturer (OEM) blades (part #M134666) deliver 15% better ice ejection than aftermarket alternatives, reducing clogging in temperatures below -12°C.
AUgment augers (part #M150396) require torque specification of 45-50 Nm during installation. Use thread-locking compound on bolts to prevent loosening from vibration, which causes uneven wear and reduces clearing width by up to 23%.
Drive System Specifications
| Component | OEM Part Number | Lifespan (Hours) | Maintenance Action |
|---|---|---|---|
| Friction wheel | M128001 | 180-220 | Clean weekly; replace if groove depth exceeds 1.5mm |
| Belt (primary) | M146159 | 150-180 | Check tension every 20 hours; deflection should be 12-15mm |
| Gear case | M117064 | 500+ | Drain and refill synthetic 75W-90 oil every 100 hours |
Chute rotation gear (part #M144191) fails most often from moisture infiltration. Apply marine-grade grease monthly and inspect for corrosion – even minor oxidation reduces throwing distance by 8-12%.
Skid shoes (part #M145321) should be adjusted so the housing clears pavement by 3-5mm. Lower settings increase traction on gravel but accelerate shoe wear by 40% compared to optimal clearance.
Deflector cables (part #M128756) stretch unevenly; replace both simultaneously to maintain symmetrical discharge. Polyurethane-coated cables outlast bare steel by 3:1 in salty environments.
Electric start kits (part #BM15185) require battery voltage ≥12.4V for reliable cold starts. Lithium-ion replacements (OEM #M155866) eliminate sulfation issues common with lead-acid units, extending service intervals to 3 years.
Locating High-Traffic Replaceable Components on Your Equipment Schematic
Start with the auger housing–scan the visual guide for components marked with numbers 12 through 18. These typically include shear pins, scraper blades, and wear plates. Shear pins (usually labeled near the gearbox input) snap under stress to protect the drive system; check for roundness at the break point if the unit stalls unexpectedly. Scraper blades (often depicted as curved metal strips) show telltale grooves when worn–measure remaining thickness against the OEM spec (normally 4mm minimum).
Next, inspect the impeller. On most schematics, it’s positioned behind the fan assembly (look for labels 22–26). Key wear items here include the impeller paddles and bearings. Paddles should have sharp, uniform edges; nicked or rounded edges reduce ejection distance by up to 30%. Bearings (identified near the shaft collar) emit a high-pitched whine when failing–replace if axial play exceeds 0.5mm. While reviewing, note the clamp collar torque spec (typically 25–30 Nm) to prevent shaft slippage.
Focus on the drive belt and pulleys (commonly grouped under section 3). Cracks on the belt’s underside or glazing on the sides signal replacement–count teeth if available; missing three or more warrants swap. Pulleys show wear via grooves deeper than 0.8mm; use a flashlight to highlight uneven surfaces. Cross-reference the belt part number with the service manual’s rpm chart to ensure correct tensioning–most models require 30–35 lbs of force at midpoint with a gauge.
Quick-Verify Checklist for Gearbox and Skid Shoes
- Remove the gearbox cover (label 40–44) to expose internal gears. Look for chipped teeth or pitting–any single tooth loss degrades torque transfer by 15%.
- Drain oil first; contaminants larger than 0.1mm indicate gear wear. Replace the 80W-90 GL-5 fluid if metallic particles exceed 2% by volume.
- Examine skid shoes (label 50–52) for flat spots or holes–OEM thickness is 6mm; replace when worn below 4mm to avoid auger housing damage.
- Compare shoe alignment bolts to original torque values (22 Nm)–loose bolts cause uneven clearing width.
Chute assembly wear concentrates on the deflection plate and rotation collar (items 60–68). The plate’s surface should be flat; dents deeper than 3mm divert material sideways. The rotation collar’s internal teeth strip easily–listen for a clicking sound during chute adjustment. Lubricate the collar with white lithium grease every 10 hours of operation; dried grease accelerates wear.
Final attention goes to the electrical harness (section 7). Inspect the ignition module and motor connectors for corrosion–green oxide forms at 1 mΩ resistance. Use a multimeter to check continuity; readings above 1.5 ohms indicate a failed switch. Lightly tug wires at connectors; frayed strands compromise spark delivery. Replace wire ties every season–UV degradation cracks standard nylon ties after 12 months outdoors.
- Print the schematic and mark measured dimensions of worn items directly on the sheet for quick cross-reference later.
- Compare notes with the OEM tolerance table–model 42 variants differ by ±5% in clearance specs.
- Store replaced components in labeled bags with the last usage hours noted for predictive maintenance tracking.