Just added a heated bed kit to a UM1. Unfortunately, I get no heat.
Everything else works (x/y/z, extrusion, nozzle heat and temp sensor). With bed temp set to zero, I get fine prints (on blue tape).
With bed temp set to 70, set point shows as 70, but measured temp stays 0. Bed stays cool.
The fact that bed reads 0, not ambient of ~20, makes me think more than one thing is wrong. If it was just the heater driver, I'd at least see ambient. If it was just a bad or disconnected temp sensor, the heater would go on (but possibly overheat).
Thermistor resistance is about 109 ohms at ambient. Heater resistance is about 3.7 ohms.
Help?
Paul