Ford 7710, Ford 550, Ford 1910, Ford 4430, KD Forklift, Ford LGT17H, New Holland L255 Skidsteer
Welcome to TBN. Individual glow plugs are tested by removing the bussbar strip connecting the plugs. With an ohmeter, test each one between the plug's post and the plug base. 1 ohm of resistance should be present on a good plug. This takes into account that you have 12 volts coming to the glow plugs when they are activated. To remove a plug, unscrew from head. Put some penetrating oil on it prior to doing so.