Trailer Wiring for 2004 S60
 

Having searched/read a number of posts, I'm posting my query here as several others were unanswered or not on point...

Can a aftermarket adapter (such as u-haul models:14486) be utilized for attaching light to trailer? (eg. t-connector 5to4 wire adapters) or _must_ a Volvo OEM Harness (part # 8698079) be used?

I've seen conflicting statements where some people 'infer' using a non-OEM unit will make the computer unhappy (voltage dips). I've also seen aftermarket (uHaul) models that are more costly but draw power directly from wire to battery I suspect to avoid just that issue.

Granted, the Volvo harness (~$100) is easy (plug in connector) -- but I've been told by dealership (and I suspect untrue) that a computer update ($$$) via VIDA is required if the plug-in OEM harness is used -- this makes the option even more costly.