HAAS® Alarm 101 — COMM. FAILURE WITH MOCON / MOCON MEMORY FAULT
Part of: our HAAS® alarm reference · covering 60 of the most common alarms.
What it means
The main control board (MAINCON) has lost communication with the motion control board (MOCON), or the MOCON has reported a memory fault. The machine can't drive anything reliably.
Common causes
- Loose ribbon or comms cable between boards
- Failed MOCON board
- Power supply to control electronics flaky
- After a power surge or brownout
What to check first
- Power-cycle once — sometimes resolves a transient fault
- If it returns, this is firmly a service call — don't keep cycling
- Stop work until diagnosed — comms faults can lead to unpredictable axis behaviour
Prevention
Communications and parameter-integrity faults are rarely caused by anything the operator did. They're typically end-of-life components or the result of a bad shutdown. The single most useful preventative step is to replace the control's backup battery on schedule (every 3-5 years) and to ensure parameter and offset backups are taken regularly.
If you’re still stuck
If you’ve worked through the checks above and the alarm hasn’t cleared — or if it cleared and came back — that’s the point to call. Persistent alarms after a reset usually mean a real component fault, and pushing through them risks turning a simple repair into a bigger one. Keith covers HAAS® breakdowns across the UK with same-day phone diagnosis.
A note on this guide. Alarm wording and numbering can vary by HAAS® machine model and software revision. The descriptions here are written in plain English to help you understand what the machine is reporting and what to check first — they’re not a substitute for the official HAAS® operator manual or for a qualified service engineer’s diagnosis. Always confirm the exact alarm message on your screen and consult your machine’s documentation before attempting any repair.