try

pays to check where crimp lugs attach to cable as well as where the lug contacts the body ( usually large deposits of green sulphate is a good warning sign of future problems)

Have the relevant bracket been fitted

the problem with led units that are fitted in original lamp holder that rely on the bayonets for connection is that the current drawn is so small that when the contact point oxidise and the led then is unable to draw current through the oxidised layer on the bayonet and then stops working...

the cable is the AERIAL

3BA on sender then 6-40

and those two sized screws were ? for the benefit of others

have you checked the ignition switch feed voltage to eliminate the switch it's self

for the R.R 14cux but may help

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take a look

try

any images of the battery connections main earth cable and the starter motor and alternator connections .have you checked the output voltage on the alternator main connection and then on the starter motor main connection and then the battery

AERIAL

on the rebuild was a discovery harness used for the engine connections utilizing the bulkhead plug etc and spliced into the original body harness or the whole vehicle TD5 harness used

have you adjusted the lumbar position to support your back

what year and when was the engine fitted as you say it's a 110 and not a td5 defender as this affects the wiring

worth a read

before condemning the battery and alternator as steve2286 said DVM. you could have loose or broken wire's to the alternator loose or badly corrode battery connector's ,badly corroded earth connection so look for corrosion on the cable crimps and signs of damage to cable's where they pass...

may help