Why Does Gildemeister CTX 210 Say Hydraulic Filter Clogged?

The “Hydraulic filter clogged” alarm remains active after the filter and oil have been replaced, and it can remain displayed even when the hydraulic system is off. On a Gildemeister CTX 210, that symptom directs the investigation away from the filter element and toward the filter-monitoring switch, its wiring, the controller input, or a retained alarm bit. Diagnose the signal path before changing DB2.DBX198.3.

Filter-monitoring signal mechanism

The term filter-monitoring switch here means the electrically monitored device mounted at the hydraulic filter. A magnetic switch can report the mechanical state of the filter indicator to the controller. The control program converts that input into the displayed alarm and may retain the alarm until a reset condition is satisfied.

Four states must therefore be separated:

State	Physical condition	Controller condition	Required action
Real restriction	The filter-monitoring mechanism indicates clogging while oil flows.	The electrical input follows the indicator.	Correct the hydraulic restriction and verify the indicator returns.
Stuck indicator or switch	The new element is installed, but the mechanical or magnetic device remains operated.	The input continuously reports the alarm state.	Inspect, loosen, reseat, and test the switch assembly.
Electrical circuit fault	The filter condition is normal.	A wiring or input fault produces the same state as an operated switch.	Trace the circuit and compare measurements with the electrical drawing.
Retained software state	The switch and controller input have returned to normal.	The alarm bit remains stored until an authorized reset occurs.	Confirm the bit’s function, obtain the required access, and use the defined reset path.

A stopped hydraulic pump removes normal flow through the filter, so a genuine flow-related pressure drop should not remain the primary explanation. An alarm that stays active with hydraulics off instead makes a stuck switch, electrical state, inverted fail-safe circuit, or retained controller bit the next decision branch.

Check 1: Live signal versus retained alarm

First determine whether the display follows a live field input or a stored alarm state. The distinction prevents an unnecessary controller write and identifies where the fault boundary lies.

1. Open the controller diagnostics without editing any value.
2. Observe DB2.DBX198.3 with the hydraulics off.
3. Locate the physical input associated with the filter-monitoring switch from the machine electrical drawing or program cross-reference.
4. Compare the physical input, DB2.DBX198.3, and the displayed alarm while the switch state is tested.

Expected reading: the physical input and the mapped program state should agree with the switch circuit’s normal condition. The inactive level cannot be inferred solely from the alarm text. A normally closed, fail-safe circuit may use the opposite electrical level from a normally open circuit.

If the physical input still reports the alarm condition, proceed to the switch and wiring checks. If the physical input is normal but DB2.DBX198.3 remains set, inspect the program logic that writes or retains that bit. If the bit is normal but the alarm remains displayed, inspect the alarm mapping and acknowledgement logic rather than the hydraulic components.

Check 2: Mechanical and magnetic switch state

A filter replacement does not automatically reset a switch that is mechanically displaced, magnetically held, incorrectly seated, or bound in its mounting. The reported repair path for this machine class includes loosening the magnetic switch and fastening it again so that it can return to its normal position.

1. Stop the machine and isolate hydraulic pressure and electrical energy before disturbing the switch or connector.
2. Identify the electrically monitored switch on the hydraulic filter assembly.
3. Inspect its mounting position, connector engagement, cable strain, contamination, and visible damage.
4. Loosen and reseat the magnetic switch without changing any undocumented adjustment.
5. Fasten it according to the filter or machine documentation, then restore power for a diagnostic reading.

Expected reading: with no clog indication present, the switch circuit should return to the normal state defined by the electrical drawing. If reseating changes the controller input and clears the alarm after acknowledgement, the switch position was the resolving branch.

If the switch remains in the alarm state, test whether its electrical contact changes when the mechanical indicator is moved through its normal test action. Use the device’s documented test method; forcing the indicator beyond its travel can damage the assembly. A contact that never changes while the indicator moves identifies a switch or alignment fault.

Check 3: Wiring and controller input

The controller cannot distinguish an operated filter switch from a field circuit fault that produces the same electrical level. A conductor short, broken conductor, loose terminal, damaged connector, missing supply, or failed input channel can therefore keep the alarm active after hydraulic service.

Observed reading	Meaning	Next check
Switch contact changes, but the physical input does not	The fault lies between the switch and controller input, or at the input channel.	Measure the circuit at successive terminals using the drawing.
Switch contact and physical input change together	The field circuit is responding.	Compare the physical input with DB2.DBX198.3.
Physical input changes, but the data bit does not	The mapping, interlock, or latch logic requires inspection.	Cross-reference every writer of DB2.DBX198.3.
Data bit returns to normal, but the display does not	The displayed alarm uses another condition or remains unacknowledged.	Inspect the alarm definition and reset logic.

Perform de-energized continuity tests only on isolated circuits. Perform energized voltage measurements only with the correct drawing, meter category, and access procedure. The expected voltage depends on the machine circuit and must be read from the electrical documentation rather than guessed.

Check the signal at the switch first and then at each connector, terminal, and controller input. The first point where the measured state stops matching the upstream state locates the fault segment. If the signal reaches the input terminal correctly but the diagnostic input does not change, test the input channel by the machine manufacturer’s approved method.

Check 4: Logic state at DB2.DBX198.3

DB2.DBX198.3 denotes bit 3 at byte 198 in data block 2. Its address does not reveal whether it is a raw input image, an internal alarm request, an acknowledgement latch, or a retained status bit. Read the program cross-reference before treating zero as the correct value.

Expected reading: when the field input is normal, the logic conditions that write DB2.DBX198.3 should drive it to the non-alarm state or permit the defined reset sequence. If another logic branch immediately writes the alarm state again, changing the bit manually will not repair the cause.

1. Cross-reference DB2.DBX198.3 and identify every program location that reads or writes it.
2. Determine which contact or comparison represents the filter-monitoring input.
3. Check for set/reset, seal-in, acknowledgement, or retentive logic around the bit.
4. Monitor the relevant conditions while the switch changes state.
5. Use the machine’s normal alarm acknowledgement once the initiating condition is inactive.

A manual write to zero is appropriate only when machine documentation identifies the bit as a resettable alarm memory and the field condition has already returned to normal. Writing zero to an unexplained bit can hide an active protection signal, be overwritten on the next program scan, or disturb logic that uses the bit for another purpose.

Check 5: Access permission and commissioning password

An access-denied message while attempting to edit DB2.DBX198.3 is a controller authorization condition, not proof that the data bit is defective. Access for the diagnostic change is obtained by setting the password in the commissioning area. The exact password and authorized access level belong to the machine owner’s controlled documentation.

Expected reading: after authorized commissioning access is established, the diagnostic interface should permit only the operations assigned to that access level. If access remains denied, verify the active user level and the machine’s access procedure; do not bypass the protection.

Permission does not make a write technically correct. Establish these conditions first: the replacement filter is installed correctly, the monitoring switch has returned to its normal position, the field input agrees with that position, and the program cross-reference shows that DB2.DBX198.3 is the alarm memory intended for reset. If any condition fails, return to the corresponding hardware or logic check.

Resolving procedure

1. Record the displayed “Hydraulic filter clogged” alarm and the diagnostic states of the filter input and DB2.DBX198.3.
2. Stop the machine, isolate stored hydraulic pressure, and isolate electrical energy required for safe switch inspection.
3. Confirm that the replacement filter and new oil service are complete and that no external condition is holding the filter indicator in its alarm position.
4. Inspect the magnetic switch, loosen it, reseat it, and reconnect its electrical connector.
5. Restore diagnostic power and observe the physical input. Expect it to match the normal switch state defined by the drawing.
6. If the input remains abnormal, test the switch contact and trace the wiring to the controller. Repair the first segment whose output does not follow its input.
7. If the physical input is normal but DB2.DBX198.3 remains active, cross-reference the bit and identify the latch or reset condition.
8. Set the authorized commissioning password when protected access is required. Use the machine-defined acknowledgement or reset operation. Write zero directly only when the program documentation confirms that action.
9. Start the hydraulic system and watch the switch input, data bit, and alarm together. Stop if the physical filter indicator returns to the clogged state; that branch requires hydraulic diagnosis rather than a software reset.

Numbered verification checks

1. Check 1: Hydraulics off. Expect the filter-monitoring switch and controller input to show the documented normal, non-clogged state.
2. Check 2: Signal agreement. Expect the physical input, the logic feeding DB2.DBX198.3, and the alarm request to change in the intended sequence without contradiction.
3. Check 3: Alarm reset. Expect the normal acknowledgement or authorized reset to clear the alarm without an access-denied message.
4. Check 4: Hydraulic operation. Expect the alarm to remain cleared after hydraulic startup while the monitoring input remains normal.
5. Check 5: Restart. Expect a machine restart to preserve the corrected normal state rather than restore the stale alarm.

Frequently asked questions