Guys, I'm building a thermostat project that uses G3MB-202P solid state relays, and have a strange issue with one of these outputs.

Basically 5v comes from the micro (in this case its an arduino) to the low voltage + pin of the SSR, with the minus pin to ground. In parallel with each SSR is a 560 ohm resistor an LED to indicate when the relay is being switched on by the controller. This is replicated four times for each "channel".

Channels 2,3 and 4 all work fine and drive the heaters correctly, but channel one is not switching the mains supply when the LED is lit to indicate it should be on. I verify that there is no power by testing with a DVM set to 500v ac, and it reads zero volts at any of the three connection points between the PCB and the actual heater. However having placed the DVM across the terminals for a second time I then get voltage and the heater gets driven for a short period and then I get the same issue again.

My guess is that it's a faulty SSR... but wondered if any of you guys had any comments to confirm that