Why Does MH 800 C Show Error 37 or 14 at Startup?

The MH 800 C changes from startup error 37 to 14 when the circuit at 16A2:33-34 is bridged or when the side doors are cycled while the hydraulic-start button remains pressed. That behavior places the fault in the startup-permissive chain: the control sees one missing condition, then exposes the next condition after the first changes state. Repeated pump-start attempts restored operation after roughly two years idle, but that result does not identify whether the underlying cause was hydraulic pressure buildup, a sluggish contactor, an oxidized contact, or a marginal interlock.

Startup symptom pattern

The number that matters is the state transition, not just the displayed number. Error 37 appears after power-up and the hydraulic-start/failure-reset sequence. Bridging terminals 33 and 34 on device 16A2 changes the indication to 14. With that bridge removed, holding hydraulic start while opening and closing the side doors produces the same change from 37 to 14.

Two independent actions therefore alter the permissive chain at the same stage. The first acts electrically at 16A2; the second operates door-switch contacts and their associated relays. Error 14 should not automatically be treated as the cause of error 37. It may be the next unsatisfied permissive revealed only after the condition represented by 37 becomes true.

Current, heat, and hydraulic timing

A hydraulic motor contactor must develop enough magnetic force to pull in and remain seated. Low coil voltage, resistance in an aged series contact, mechanical drag, or a contaminated pole face can slow pickup. A partially seated AC contactor can draw excessive coil current and heat rapidly. This is heat, not logic: repeated pressing may temporarily make the machine run while continuing to stress the coil and contacts.

The hydraulic system adds a second timing path. After a long idle period, oil distribution, valve position, pump priming, and pressure-switch operation can delay the pressure permissive. Repeated starts may eventually produce the required pressure indication. Separate that condition from an electrical pickup fault by observing the pressure device and measuring the contactor coil at the same instant. A contactor that pulls in firmly while the pressure permissive remains false points downstream toward the hydraulic circuit. A contactor that chatters, sounds sluggish, or loses coil voltage points upstream through the electrical permissives.

No conversion from button-hold time to a safe duty cycle is possible without the contactor data and motor-starting information. Read the coil rating from the contactor, the motor current from its nameplate, the overload setting from the protective device, and the permitted operating cycle from the component documentation. Stop repeated start attempts if the contactor chatters, the coil or wiring heats, insulation smells, or the motor protection trips.

Error-code and drawing interpretation

Use the machine-specific electrical drawings because hardwired error assignments can vary. Locate the error-indicator sheet, find the displayed code, and follow its cross-reference to the circuit section that generates it. One documented drawing convention resembles 37a1/57 264: 57 is the displayed code and 264 directs the technician to the generating circuit section. Treat that string only as an example of how to navigate the drawings, not as the cross-reference for this machine.

Error 57 has two reported descriptions for this equipment family: a startup-failure indication expected to clear after the oil pump starts, and an indication associated with the safety-switch or emergency-stop interlock domain. Those descriptions can coexist if the display reports the failed startup stage while hardwired safety contacts are what prevent that stage from completing. On a machine where 57 remains after hydraulic startup, trace its actual generating circuit instead of accepting the label alone.

Identify the installed controller before applying controller-specific diagnostics. The possible controls raised for this machine were 432 and 532; a separate installation used a Philips 432. Read the controller designation on the installed hardware. Also check the main console for an error indication in addition to the side display, because the two displays can represent different layers of the startup sequence.

Controlled diagnostic procedure

1. Return the circuit to the drawing. Record every existing bridge with terminal numbers and photographs, then compare it with the machine-specific schematic. Remove undocumented bypasses through the proper repair process before evaluating normal safety behavior. Do not operate production motion with guard, emergency-stop, overload, or hydraulic permissives defeated; an unexpected start or unguarded axis movement can injure personnel.
2. Record the exact sequence. Power the machine, press hydraulic start and failure reset using the documented operating sequence, and write down which display first shows 37. Note whether reset must be pressed once or twice and whether the code changes only while hydraulic start remains held.
3. Trace code 37. On the error-indicator sheet, follow the cross-reference for 37 to its generating section. Mark every series element from the control supply through the relay or input that creates the error.
4. Inspect 16A2:33-34. Determine from the drawing whether these terminals belong to a relay contact, switch, or another device. With power isolated for resistance testing, operate the related device and verify that the contact changes cleanly. With power applied under the machine's approved service procedure, measure voltage on both sides during the failed start.
5. Exercise each guard normally. Observe the schematic-defined door-switch and safety-relay states while opening and closing the side doors. A contact that changes only when the door is pushed, lifted, or moved beyond its normal latch position needs mechanical alignment or replacement, not a bridge.
6. Test contactor pickup. Measure directly across the hydraulic contactor coil from immediately before pressing start through pickup. Compare the reading with the coil nameplate and drawing. If voltage is low, move upstream one series contact at a time and measure voltage drop to find the resistive connection.
7. Separate electrical pickup from hydraulic proof. Confirm whether the contactor closes fully, the pump motor runs, and the pressure permissive changes state. Follow the machine's hydraulic service information if the motor runs normally but pressure proof does not arrive.
8. Check stored-energy protection and maintenance items. Inspect the motor-protection device for a trip or incorrect setting and compare its setting with the motor data. A machine idle for about two years also warrants backup-battery service using the controller procedure, but battery maintenance is separate from proving the hardwired startup fault.

Decision path after the first code clears

Repair verification

Verification requires repeatable cold and warm starts with the original wiring restored. Close all guards, release every emergency-stop device, reset the protective circuit, and start hydraulics through the normal controls. Confirm that 37 clears without touching the doors, bridging 16A2:33-34, or holding the button beyond the intended command.

Repeat the test after opening each guard individually. The safety circuit must prevent or remove the affected machine permission as defined by the drawing, and normal operation must return only after the guard is closed and the required reset is performed. Confirm that error 14 does not appear as a residual second fault.

During several starts, listen for a single decisive contactor pickup rather than chatter or delayed seating. Record coil voltage, pressure-permissive state, displayed code, and protection status for each attempt. Recheck terminal temperature and connection tightness after testing under an electrically safe service procedure. A week of improving behavior after repeated starts is not acceptance evidence; stable startup from a cold, untouched condition is the relevant test.

Recurring diagnostic pitfalls

A bridge that changes the code is a localization test, not a repair. Leaving 16A2:33-34 shorted can conceal the contact that is supposed to prove a safe or ready state. Unknown custom jumpers require line-by-line comparison with the original schematic because one may bypass a guard while another masks a hydraulic or protection fault.

Changing error numbers can be mistaken for an intermittent display. In a series permissive chain, the controller commonly reports the condition currently blocking progress. Satisfying that condition exposes the next one, so 37 followed by 14 can represent two genuine faults or two incomplete stages.

Repeated button presses can also mislead troubleshooting. They change contact temperature, scrape oxidized surfaces, cycle a sticky armature, and give the hydraulic system additional opportunities to establish pressure. Capture voltage and contact state during the first cold attempt; measurements taken only after the machine begins working can hide the defect.

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