how can i find out what is wrong with my fiat 2.8 diselducato 14 heater plu?

i have a fiat ducato 14 1998 s reg diesel .the glow plugs are not working. i have traced the relay for the plugs & have got a feed at the relay but the switching current for the relay is not there when i switch the ingnition on.the glow plug warning light on the dash does not work.if i bridge the relay (main terminal to the glowplugs for a second or two the plugs work ok. i think there must be a water sensor switch or somthing wrong ???.please could you help.
john atkinson, March 2005


done
If you have input and no output..one would suspect the relay ,possibly burnt ...one could wire in another relay..as this one isnt that cheap.....

lobofuego, December 2005
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