Glowplugs taking a long time SD22 720

[docdillio]

my glowplug relay (and GP dashlight) don't switch off until about 30-40 seconds after I turn the key to energize the glowplugs. I'm getting around 10V at the GP's and then the voltage drops to 0 when the GP relay switches (and thunks). I'm not convinced the GP's are getting very hot. Could it relate at all to the water temperature sensor at the thermostat? the wires have been cut since I bought the truck. (but the thermal transmitter at the thermostat is connected.) any thoughts or advice is greatly appreciated.