We are experiencing a problem where the mechanical switch of a SPST NO relay (COTO 9007-05-01) is not opening back up when the coil is de-energized. Current keeps flowing through the switch until we give the relay a (somewhat gentle) flick.
We measured voltage and current on an o-scope (a Tektronix current probe for the current), and everything appears to be in order: On/Off voltage connected to coil appears good, On/Off current through the coil appears good, on-current through the switch well below rated current, open voltage across the switch well below the rated voltage, no unreasonable spikes, the coil has a fly-back diode installed…
We even replicated our setup with different everything (including relays) and got the same results.
Any suggestions on what to do/check?