Good news. Heat Tape Pro and Pipe Freeze Pro are the only heat cables in the world you can see is working. The GlowCap™ is the LED end cap used to terminate all of our pre-terminated heat cables. If you see the green light glowing at the end of the cable, the cable is working. We also offer a GlowCap™ End Seal Kit for field assembled cable systems. Another quite obvious way of determining if your heat cable is working is to feel if it is warm.