Stereo Microphone Output into Mono Input
@maxmclau The so called dual-mono configuration seems to provide a (sometimes independently controllable) copy of the monoral camera audio output, allowing this to be used for e.g. unforseen strong audio bursts during non-repeatable shot-taking. Likely (no more than that) the 3.5mm TS-TRS-adapter piece can help you out. I suspect that the TRS connection is of the conventional Tip=signal1, Ring=signal2, and Sleeve=ground/screen, with the Rode taking signal1 and signal2 as the two mono outputs. The TS configuration in your car-unit may contain shorting switches which makes a short-circuit between signal1 and/or signla2 to ground. The adapter piece you suggest may overcome this. Give it a try!