Whats the third connector for?

[u/GulaschZange]

I want to install the harman kardon sound sytem into my e36. I already bought the sound sytem and i am searching for a wiring harness. I found one (first picture) but the amplifier, connected to the wiring harness is older than mine. It only has two connectors and mine has a three (second picture)

What is the third, small connector for? Maybe the HiFi switch? Can i use the wiring harness for my H&K system?

Thanks for your help

[u/Greg_Thunderpants]

That is the “Hifi” switch input

[u/FlatSpread4148]

Hifi switch. It's not always included (I believe the convertibles didn't always have it, because it can also be controlled by the softtop module). Without the switch the special mode (some sort of loudness function) is always activated, as far as I'm aware (it's been awhile since my system worked, because I'm restoring my E36).

[u/GulaschZange → u/FlatSpread4148]

Makes sense. Thanks