I have a Kubota L4610HST. When starting I turn the key to light the glow plug light, when it goes out I start the tractor. Then the light will come on again, after a few seconds it will go off. Then it will come on again, at this point it will usually stay on. I have replaced the water temp. sensor in the thermostat housing. I can also hear the glow relay click off. Anyone have any info on this. Thanks