2001 Hummer H1 glow plugs not heating---glow plug controler

the glow plug relay is located on the left rear of the engine, it will have two red large wires going to it, take a test light put it on one of the red wires, have someone turned the key on and you should have power or about 10 seconds, if no power repeat the procedure on the other wire, if no power checked your wire connections, if you have power(you will hear the relay click on and off) the relay could be bad, but they are very heavy-duty relays, have you checked your glow plug to make sure they're not burned out?