Perkins 4108 faulty Lucas alternator fix

The Perkins 4108 46hp diesel is a super four cylinder marine motor,it was made for marine use,not cobbled from another makers truck and dubbed marine but it still has parts on it that are just the same as the general auto makers use.

The Perkins 4108 must have been issued with a generator,then later installed with a Lucas alternator,I say this as when I got the engine it had a secondary wire loom and a mount plate that was suitable for the older generator,those wires I eventually removed when I rewired the engine to switch panel.

I ran the engine on saturday,all was well excepting the alternator was not charging,I took out a spare Bosch unit,same size and around 35amps,not a huge output but reliable,the plan was to take the Lucas one off and do a change over.
                                         
Thinking this over that evening I though to first check the panel warning light,which on an alternator is also an exciter lamp,without which the alternator will not work.It was my lucky day as thats all it was,with a new one installed,yes I have spares on board,the main engine was soon recharging the boats batteries.

Clearly blown as the dark glass indicates.

So save your self a stack of work,get spare bulbs and when and if the alternator stops charging,check the bulb first.

Roy