surge

Surge, do you mean when you connected the caution light that the running lights then don't go off between flashes

And does the caution light now also behave the same way

they never go completely off they get dim as the caution light goes on

they never go completely off they get dim as the caution light goes on

Sounds Surge like it's miswired, perhaps in series instead of parallel. That is to say its return wire is connected to the hot side of the running lights

Surge, I am not sure if by your question you want the both the running lights and the caution light to flash or just the caution light. If all the lights should flash is it possible the flasher unit is not heavy-duty enough. I have seen this with a truck and trailer where a flasher unit does not work properly with the addition of lights. If just the rear caution light is meant to flash then as mentioned you may have a wiring problem that is causing the voltage to drop on the running lights each time the caution light is on.

The light should go on and off.. Check the wire connection ... or contact a mechanic.