Gauges (Pneumatic and Hydraulic) Troubleshooting Guide

Introduction

Pictured is a common style of gauge used in the hydraulic and pneumatic systems of a Haas machine.

Symptom Table

Symptom	Possible Cause	Corrective Action
Fluctuating gauge.	Internal components are worn or damaged.	You must replace the entire gauge assembly.
Gauge does not read the correct pressure or does not return to 0 PSI.	Incoming pressure to the gauge assembly is not correct, snubber not in place.	Verify components that generate incoming pressure to the gauge assembly are working correctly (i.e Hydraulic - Hydraulic pressure unit; Pneumatic - air compressor), verify the snubber set screw is in place.

Fluctuation

Fluctuations of up to 50 PSI are normal for operation of the hydraulic power unit (HPU). The fluctuations do not affect machine operation or performance. For larger surges in pressure, check for oil contamination or a low oil level.

Possible Cause: Internal components are worn or damaged.

Internal components will get normal wear and tear from the constant movement of the pointer across the scale.

Corrective Action: You must replace the entire gauge assembly.

Remove the incoming pressure to the gauge assembly. Rotate the gauge counter-clockwise to remove it. Gauges that do not have clearance to remove by rotation have swivel fittings [2]. Use two wrenches to hold the fixed portion of the adapter fitting [1], and another to turn the swivel fitting [2].

Verify you have the correct gauge for replacement (scale, fittings, etc). Check for the snubber and install the new gauge assembly clockwise and tight. Be sure to use thread sealer when needed.

Incoming Pressure

Possible Cause: Incoming pressure to the gauge assembly is not correct or the snubber is missing.

Corrective Action: Verify components that generate incoming pressure to the gauge assembly are working correctly (i.e Hydraulic - Hydraulic pressure unit; Pneumatic - air compressor).

Most gauges will have an inline pressure regulator for the incoming pressure. Verify the regulator allows the correct amount of incoming air pressure.

Some regulators are adjustable. If it is adjustable, adjust as necessary. If it is not adjustable, the regulator can be cleaned or replaced.

Remove the pressure gauge and check that the snubber set screw [1] has not backed out. The snubber set screw is similar to the Haas Liquid Grease restrictor fitting. Re-install the snubber set screw without any thread locker. Replace the gauge as needed.