The glowplug indicator light and the 'click' of the relay turning off should not coincide. The time the glow light stays on is determined by temperature whereas the relay is on a fixed schedule of around 40 seconds usually. Test it. Turn the key on. Watch the glow plug indicator light go out. Put your ear next to the relay and see if you can hear it click off after about 40 seconds from when it was turned on.
The flashing light is an indicator something is not right with the system. Why were the glowplug wires replaced. They rarely fail.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13