Seimens Cerberus pyrotronics ZU-35

New to the fire panel world. have a old System 3. one of the ZU-35 duel zone module have a trouble light on. System is monitored off site at 2 locations both show no trouble. light seems half lite. Any suggestions what to look for or could it be bad module.

is there a trouble light on the cp-35?

Yes. It is a common trouble LED as well as two zones built in (alarm & trouble LED’s for each zone). Any trouble on the system will cause it & the sonalert to turn on.

If any expander module goes into trouble, the expander cards trouble LED should turn on as well as the common trouble LED on the CP-35.

looks like the original post got deleted, someone was asking about a bad zu-35 iirc.

Sounds like a bad EOL on the zone with the dim light or the module could be bad. The EOL for ZU-35’s is a 50 micro farad capacitor which tends to dry out over time.

It might not be dried out enough to trigger the common trouble buss. If you lift a wire off the ZU-35 (terminals 2 & 5 or 8 & 11 if class B) does the CP-35 show trouble?

I have seen this caused by an EOL fail and also a bad trace on ZU-35 itself.
Good Luck.