Quote taken from a SEME Bordon literature dated 1990:coffee:--When running pack up outside vehicle,always have transfer box disconnecter engaged and remove prop,with it disengaged only safe to run for 3 mins:nono: due to build up of oil in t/box,I think this is where you re coming from.
In the late 60,s/early 70,s we used to run these things up for ages to get the temps up especially if you had fitted and were testing a new g/box on a rig,happy days?:cool2:
On your problem ,check the simple obvious things first,circuit breakers/fuses, loose or disconnected wires etc after that it,s like Mike says go through with a cicuit tester.
Any probs give me a call 07711245690 I have got some SEME fault finding literarure which has helped me in the past
good luck
DaveP