I have a couple of VMB4RY modules now which have failed in the same way, specifically that the output of relay 4 flickers on and off several times per second (but not a regular frequency) when the relay should be set to “on”.

One of these was attached to a couple of CFLs and only on intermittently, the other was attached to a small valve (so a inductive / coil load) set to be on constantly.

  1. Is this a common failure mode and 2) (as they’re well out of warranty) any repair tips?



First check the velbus power supply. At overload the supply voltage drops below the holding voltage the relay.
In case of inductive loads, it’s better to use a extra high power relay to drive these loads.