Disco 2 Wiring in rear door subwoofers to aftermarket head unit

My 1999 D2 ES has the Harmon Kardon Hi Line entertainment system, although the original head unit has been replaced by a modern system that gives me Bluetooth and phone connectivity. The subwoofers in the tailgate door were kaput, so I have replaced them with a working used unit, but still no sound.

The new headunit supports subwoofers, but through separate RCA connections. I assume that all speaker connections originally went to the multiplug which is now connected to the new head unit through an adapter loom.

Am I right in thinking that if I can identify the subwoofer wires in the original multiplug, extract them, and fit RCA connectors, that it should be possible to get them working again?
If so does anyone know which wires?

That will be the audio to start with ,then there’s the the amps two 12v supplies, one permanent and the other for the amp switching on-off both of them originated at the head unit.
The wiring 12v supplies and the audio to the tail gate will be existing so yea they will have to be identified, after that just reconnect both ends as necessary and switch on the head unit and balance it’s pre-amplified output to the tailgate amp. Simples

The tailgate speakers are driven from the Harmon power amplifier under the front passenger's seat, not from the head unit.

brian47 said:

The tailgate speakers are driven from the Harmon power amplifier under the front passenger's seat, not from the head unit.

Click to expand...

Oh well my post was a waste of time then. I’ll make a note not to bother again in a lunch break, so back to work.

So my issue is connecting the output from the new head unit to the HK power amp?
Any idea how the amp was connected to the original unit ie. what am I looking for behind the dash?

From looking at the drawings, I would surmise that there was no actual "sub-woofer" or Bass output from the head unit. The audio outputs from the head were just the normal front/back, right/left outputs which were fed to the power amplifier.
The low frequency filtering and amplification was then applied within the power amplifier and then fed to the tailgate speakers as a separate feed.
I've attached the Hi-line Harman drawings for you:-

Thanks for that. Assuming the new head unit does not bypass the amp entirely, (and why would it, wiring the speakers would be much more complex?), it looks as though live feed to the sub woofers are controlled by the red and white cables from the original head unit. These should be still in place in the original multiplug, but presumably doing nothing as the new head unit only supplies a sub woofer output through separate RCA plugs. At the weekend I'll have a look and see if It can splice an RCA feed into the original side of the multiplug. Cheers.