Problem with 9481 giving no output - using 9485 instead?

[SamF42]

Grad student in lab with a high temperature reaction vessel. I inherited a Labview code and cDAQ chassis with two modules from a previous student in my lab. I have a code which uses a NI 9219 to read a thermocouple, and then based upon that temperature, the code turns on heating tape through a 9481. There's an external thermocouple that makes sure the heating tape turns off once it gets too hot.

This has worked just fine for two years, but now the 9481 is not actually turning on my heating tape. The indicator light still turns on, but I've got no current going through. I've tested multiple heating tapes, so they're not the problem. I don't know if I have actually flipped a switch in the code or if the module is just physically broken. 

I have a spare module of a 9485 that was purchased as a backup, but when I plug that in in place of the 9481, nothing happens. I don't know if that needs a different boolean switch to turn on. I don't have too much coding experience, so I hope this is a trivial problem. Any advice would be greatly appreciated!

[Electromecha]

If the relay light on the 9481 is on then the relay is closed and actuating. 

I would suspect your external circuity is not ground referenced properly for current to flow. 

You could test the relay by disconnecting your wiring and placing an ohmmeter across the output terminals.  It should read very low resistance (ohms) when the relay is closed and open circuit when the relay is open (megaohms).

Good luck.

[SamF42]

Thanks for responding. I connected an ohmmeter across the terminals and I got no signal. I checked the ohmmeter and it worked with other circuits. The relay light still responds to the code, when I turn the heater on or off, but it's not creating a closed circuit. 

[SamF42 · Accepted solution]

I ran a test of each of the channels and there's definitely a quieter 'click' when the first channel turns on compared to the others. The ohmmeter gave me a signal when I turned the other channels on. I think there is just something broken, so I'm going to use the next channel.

Update: Second channel is working fine.