Indest IS70C light stays on?

Hi everyone,

This appears to be a common problem with this dryer: the water tank is empty but the light is on anyway so I'm not getting any heat out of the dryer. I've tried tapping the back of the grey box on the back to reset the float, and manually resetting the light with the cover off, one of which appeared to work for about half an hour of operation before the problem reappeared. Then I tried resetting the thermostat but that didn't do anything at all. Is there anything else I can try before I start replacing part?