Skip to main content
Electronic Theatre Controls Inc

CEM+ Reporting Overtemp Error


CEM+ is displaying Overtemp Error(s)

Explanation of Issue

This issue is most often caused by one or more dimmer modules, rather than the CEM+. The CEM+ circuitry receives overtemp signals from the dimmer modules and is not designed to generate an overtemp signal. It is far more likely that a CEM+ would not detect an overtemp if the comparator on the CEM+ fails.

It is possible that corrosion around the comparator on the CEM+ can generate an overtemp signal. However, though there would likely be other problems with the CEM+, and possibly the rack, if corrosion is found.

When a dimmer's internal sensors indicate it is running too hot, it sends the signal to the CEM+, which then reports that an overtemp is occurring. Dimmer modules which are reporting an overtemp can be hot enough to cause burns when touched.

Additional notes:

  • Overtemp is not an AF function. Overtemp errors are generated independent of AF cards that are in the rack
  • Overtemp messages only appear after the dimmers are brought up above a level of zero
  • Overtemp is a bussed signal. This means that if a module is reporting an Overtemp error, it can cause Overtemp errors for adjacent modules to appear


Caution-Icon.png It is recommended to de-energize the rack to unseat and re-seat modules. Seating modules while energized could could cause damage to either the rack and/or the dimmer modules
  1. Check the CEM+ overtemp error to determine which module is reporting the signal
  2. De-energize the rack. Pull the CEM+ to check for any corrosion damage. If no corrosion is visible, re-seat the CEM+ and proceed to step 3.
    1. If corrosion on the CEM+ circuit board is found, inspect the rack and modules to see if more corrosion exists and proceed to step 7
  3. Unseat the suspect dimmer module. Leave the module in the rack but unseated so the slot isn't fully open
    1. If there are multiple suspect dimmer modules, unseat all the suspect modules
  4. Re-energize the rack. If an error returns, clear the error on the CEM+ (may need to hold clear for 10 seconds), and check if the error returns again. Return to step 3 and de-energize the rack as necessary
  5. Re-seat each dimmer module one at a time and set the dimmers to above 0% (20% is a good starting point), de-energizing and re-energizing as recommended
  6. If the error does return, note the dimmer module, unseat, then continue testing the adjacent modules one at a time in case they are bad. Again, leave the modules in the rack, but unseated, so the slots aren't fully open
    1. Modules can also be swapped to other slots to see if the error follows the modules. If multiple modules are reporting errors, remove those modules together and move them to other slots, keeping them together
  7. Contact ETC to begin the RMA process for any problem units
  • Was this article helpful?