heater plugs

1993 ford escort estate diesel have had fuse box faults - various for 2 months - am having recon fitted saturday. heater plugs have not worked for last couple of days - hope the fuse box solves this. heater plug flashed on a couple of times whilst driving once. next day ok until afternoon - not working. have worked intermittendly since. is this a sign of plugs going - hope its just the fuse box.

thanks

mark