Alarm 37 fires when the hydraulic pressure switch detects system pressure below the minimum threshold required for safe operation of tool changer, spindle clamp, and other hydraulic functions. The NGC control monitors hydraulic pressure continuously and will halt machine operation to prevent damage from inadequate clamping force or failed tool changes.
HaasPower SupplyIntermediate60-120 minutes
37
HAAS Alarm 37 - Low Hydraulic System Pressure
Hydraulic system pressure too low
This alarm triggers when the hydraulic system pressure switch indicates insufficient pressure for proper operation of hydraulic components such as drawbar, brake, or gear changer. The MOCON monitors the hydraulic pressure switch input and requires adequate pressure before allowing operations that depend on hydraulic actuation. Loss of hydraulic pressure during operation will immediately halt the machine to prevent tool pullout or brake failure.
Root Cause Summary
Alarm 37 fires when the hydraulic pressure switch detects system pressure below the minimum threshold required for safe operation of tool changer, spindle clamp, and other hydraulic functions. The NGC control monitors hydraulic pressure continuously and will halt machine operation to prevent damage from inadequate clamping force or failed tool changes.
Safety
Hydraulic systems contain fluid at high pressure; do not loosen fittings while system is pressurized
Hydraulic fluid can cause severe injection injuries if it penetrates skin; do not test leaks by hand
Ensure pump motor is disconnected from power before servicing or replacing the pump
Causes and Fixes
1
Check hydraulic fluid level
Open electrical cabinet and visually inspect the hydraulic reservoir tank. Fluid should be between MIN and MAX marks on sight gauge.
Ensure machine is powered off and locked out before opening electrical cabinet
2
Add hydraulic fluid if low
Use only Haas-approved hydraulic fluid (typically ISO 32 or equivalent). Remove fill cap and add fluid slowly to MAX line.
Check fluid color - dark or contaminated fluid indicates need for complete system flush
3
Cycle hydraulic system
Power on machine and observe pressure gauge. Normal operating pressure should be 800-1000 PSI depending on machine model.
If fluid level drops quickly after refill, suspect major internal leak
1
Locate hydraulic filter assembly
Find the spin-on hydraulic filter in the electrical cabinet, typically mounted near the hydraulic pump motor.
Filter should be changed every 2000 hours or annually, whichever comes first
2
Check filter bypass indicator
Look for red bypass indicator button on filter head. If extended, filter is clogged and bypassing.
Never operate machine with bypassed filter for extended periods
3
Replace hydraulic filter
Power down machine, relieve system pressure, and replace filter element with Haas part number specified in maintenance manual.
Pre-fill new filter with clean hydraulic fluid before installation to prevent air ingestion
4
Reset system and test
Power on machine and monitor pressure buildup. Pressure should reach normal operating range within 10-15 seconds.
If pressure remains low after filter change, suspect pump wear or internal leakage
1
Listen for pump operation
Power on machine and listen for hydraulic pump motor operation. Pump should run continuously until pressure is reached, then cycle on demand.
Unusual pump noise or continuous running indicates internal wear
2
Check pump motor current draw
Use clamp-on ammeter to measure pump motor current. Compare to nameplate rating - low current may indicate pump slippage.
High current draw may indicate seized pump or electrical fault
3
Verify pump pressure output
Install pressure gauge at pump outlet to isolate pump performance from system restrictions.
Pump should generate full rated pressure with minimal flow demand
4
Replace hydraulic pump if faulty
If pump cannot generate adequate pressure, replace with genuine Haas replacement pump assembly.
Pump replacement requires system flush and proper bleeding procedure
1
Inspect for external leaks
Visually examine all hydraulic lines, fittings, and cylinders for signs of fluid leakage or wet spots.
Use flashlight to check hidden areas behind spindle head and tool changer mechanisms
2
Check hydraulic cylinders
Inspect spindle clamp cylinder, tool changer cylinders, and any optional hydraulic workholding for seal leakage.
Leaking spindle clamp can cause catastrophic tool pullout during machining
3
Test system pressure decay
Build system pressure and shut off pump. Monitor pressure gauge - rapid pressure loss indicates significant internal leakage.
Normal system should hold pressure for several minutes with minimal decay
4
Repair identified leaks
Replace faulty seals, tighten loose fittings, or replace damaged hydraulic lines as needed.
Use only genuine Haas hydraulic components to ensure proper pressure ratings
1
Verify actual system pressure
Install calibrated pressure gauge at hydraulic manifold to confirm actual system pressure independent of pressure switch.
Normal operating pressure should be 800-1000 PSI depending on machine model
2
Test pressure switch continuity
Disconnect pressure switch wiring and test switch contacts with multimeter while observing system pressure.
Ensure proper lockout/tagout procedures before working on electrical connections
3
Check switch adjustment
Verify pressure switch is set to correct trip point per machine specifications, typically 600-700 PSI minimum.
Some switches have adjustment screws that may have drifted over time
4
Replace pressure switch if defective
Install new pressure switch with correct pressure rating and electrical connections per Haas wiring diagram.
Incorrect pressure switch rating can cause nuisance alarms or unsafe operation
