96 passat glow plus not comming on

[passat larry]

I ahve a 1996 Volkswagen Passat 1.9 tdi and the glow plugs do not come on any more .I have removed the engine temperature sensor (ECT) and the glow plugs come on for maximum timing and the cars starts as normal.I went and installed a dealer temp sensor and plugged it in but the same thing happens again,no glow plugs come on and it will not start.I have now changed the relay under the dash and still no glow plugs operate with the keyswitch.Why does the system work when temp sensor is unpluggged ,does the relay not work then?I am desperatly trying to figure this problem out and am new to this site.I would appreciate all the help I can get and maybe I can return the help to someone else down the road ,thanks Larry