Good evening. I was hoping someone with better knowledge of electrics could assist please.
I have a 110 to which someone has fitted LED rear lamps. Square ones when the lamp manufacturer makes round ones. The RHS indicator refused to work when I collected it. There is one green/white cable for the feed and a black for earth. Into the green/white lead, between feed and lamp, someone has fitted a length of two core cable. This disappears into the back of the body where it is connected to a large heat sink/resistor. This has three cables, black for earth, a green and then a yellow. These two are connected to the length of cable coming up from the green and white. I presume that the power from the loom into the green and white is fed into the resistor/heat sink and back to the lamp, thus creating the current draw that the system needs. The same is fitted on the LHS which is working fine. There is another length of two core cable that has been spliced into the main loom and this is connected to a small black relay, the numbers on which are indistinct. Now I could just bypass the resistor/heat sink as the original green/white cable does have power but there's nothing coming down to the lamp from the resistor. That's the problem with electricity I suppose, it's there but one cannot see it. I can take photos if required. I should add that the front indicators are the original bulb type.

Unfortunately adding the colour code of the wire means nothing without a wiring diagram of the installation. The introduction of a resister to the circuit is just used to return the indicator flash rate back to normal and similar to a normal 21w incandescent bulb being fitted.
All u need to do is check wiring, that’s a positive feed from source to the LED lamp, i assume you would pickup the ground/earth local to the lamp, u could have an iffy/ incorrect resistor, check product specifications do u have one or two and are the resistance values correct.

Thank you. I have wired the lamp to a battery and it works fine. There is power in the original wiring but somehow it disappears in the diversion via the load resistor. Is it possible to check these individually?

Just to update the post. I managed to persuade an auto electrician to take a look. He bypassed the resistor, installed a 21W bulb in its place and everything was fine. Clearly the resistor was the problem.