Suggested experiment - hook the SSR up to the power supply and heated bed, but don’t turn it on. Then see if there is current flow. My guess (if you don’t see current flow) is that what you actually got (due to poor counterfeiting) is an AC control device.
I tried the test you suggested, even without the trigger signal, it’s reading 1.3v across the two SSR Terminals.
I’ve ordered a Mosfet. Hopefully won’t take too long to come…
Okay, unit is seriously bad. I hope its not too late to get your money back
or otherwise raise a fuss.
Just to update everyone.
The FOTEK was certainly counterfeit.
I tore it apart to see what’s inside…
It was supposed to be a 40A DC SSR. The transistor was a ST BUF410
and here’s the datasheet
It’s a 15A transistor sold as a 40A.
Are these counterfeit companies trying to burn down houses?
I salvaged the screw terminals to make a Mosfet based relay. I’ll post it up soon.