I just replaced the thermistor on my workhorse, and now when it starts heating the screen shuts off. No spark, but the top fuse blows. I know it’s a short, but I can’t figure out why it’s happening. I only disconnected the old thermistor and plugged in the new one. Nothing else really changed. Help! 
My guess would be that you broke a heater wire or cause a short in those wires when doing the thermistor.