I’m so confused. Last night my printer was fine. This morning the bed won’t heat. I have it wired to an external power supply through a 100A SSR. The power supply is 12v, 400w.
The SSR light comes on, so the switch signal is fine.
If I wire the bed heater direct to the supply, it works fine. If I wire a 12v fan in place of the heater, the SSR will turn it on and off fine.
Using a multimeter, if the SSR is on, I get 12v.
It’s like I’m getting voltage, but no amperage. Is that even possible? If I blew the power supply somehow, I would expect to get anything at all. Same with the SSR. I’ve rechecked the wires themselves and they seem fine.
Are you measuring 12V at the leads going to the heater, or 12V open-circuit with the heater disconnected. If a load is connected to a 12V supply, the current going through it will be 12^2/R Amps, where R is the resistance of the load. In order for less current to flow, either the resistance has to be increased or the voltage has to drop (which is the failure mode for a power supply that can’t supply enough current). You could also try putting an ammeter in series with your heater to check the current, but if the resistance is remaining constant, the voltage while it’s being powered should tell you that.
I checked the voltage across the outputs on the SSR. I also checked voltage between leads on the power supply itself. Not sure how to check the heater other than hooking it direct to the supply, which worked just fine.
The SSR is only 2 weeks old, but some flaw in that is all I can think of. (Which is irritating, since its new and took 10 days to get here.)