Mystery plug on Radio Harness, no power to radio

Technical Area Electrics & ICE
1

New here and new to MX-5 ownership so very grateful for your help.

My car came without a head unit. I bought a new one and I’ve just tried to install it using a harness adaptor from MX5Parts. After connecting everything up, the head unit isn’t getting any power. I have checked the fuses and all are fine.

There is a mysterious black plug attached to the car’s radio harness and I’m wondering if it could be related to the problem. It looks like a previous owner has wired up a subwoofer at some point in the cars history because there are red and white cables in the dash.

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There is no space for this black connector on the harness adaptor.

Any ideas what I can do to get the head unit working? I’ve attached some pictures.

  1. My model of MX-5 is: MkII 1.8
2

Did it have Bose previously?

All you need is the white loom plug to connect the head unit up. If you have an aftermarket head unit then you need the ISO adapter, sounds like that’s what you have from Mx5parts.

I mentioned Bose because if it did have it there’s another connection to be made to bring power to the head unit, to power the amps up.
It’s been a while since I wired a Bose fitted Mk2 up, it’s easy enough when you’ve found the correct wire, ignore all this if no Bose of course.:+1:

3

Cheers for the help Mick, I’m not sure what system the car came with originally. Sounds like this could be the issue though! I will try and find details of the extra connection that’s needed online.

4

Mine was an imported Mk2 with Bose, the radio worked (as in there was power) but it was tuned to Japanese wave bands.:dizzy_face:
But when I came to install an aftermarket head unit, nothing, no power. Finding a live feed to the correct connection did the trick.
You need to say which model you have Mk2, I’m not sure which came with Bose, the top end ones if any I think or imports.

5

Managed to get the head unit powered up. Connected a loose wire from the back of the head unit called ‘P-Cont’ to the mystery black box which seems to be a 12V source. This wire is described in the manual as intended ‘to the power control terminal when using the optional power amplifier’.

Slightly concerned it will drain my battery because I doubt this 12V source is tied to the ignition but we’ll see.

Cheers for the help I’ll be back when it all goes wrong. Look forward to being a part of the MX5OC community.

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