Under the air cleaner is this controller & another relay. The glow plug indicator light dims when thre relay clicks & then brightens when it clicks for the second time. Is the controller telling this relay to open & close but the circuit to the indicator light is not opening?

under the air filter hosing is the glowplug controller. it will be faulty and will probably burnt out the glowplugs. check that the throttle cable is free and not tight when pressing the pedal ,it could be seizing up