Odd Jobs

Converter’s socket

The Peugeot Boxer, Citroen Relay and Fiat Ducato can be equipped with an option for a “Conversion Interface” or Converter’s socket.

Fiat: “Electrical Interface Supply Socket (For Conversions)” option 081

Peugeot: “Electrical connections interface box / Includes reinforced alternator” option JI01

Citroen: “Conversion interface box”

These connections are intended for use by vehicle converters who wish to interface with the vehicle electrics. Even if these options are not specified on a new van, quite a few people have found the converter’s sockets installed anyway. The sockets offer a few things which may be of some use if you’re converting one of these vans:

  • A switched 12V signal which is live when the ignition is on (KEY+)
  • A charging signal (from which a D+ “charging” signal can be obtained)
  • High current connections to the cab battery
  • Rear speaker connections

All of these things can be picked up elsewhere, but the converter’s socket provides a convenient place to get these and one which hopefully won’t cause issues with the warranty on a new van (the main reason we had for specifying this option on our van).

The following isn’t official advice or definitive information – your van might be totally different! It’s just a summary of what I’ve found to be relevant to our van (a 2018 Citroen Relay). Please check carefully – I won’t be held responsible if something goes wrong!

The sockets are located at the bottom of the (UK) driver’s side ‘B’ pillar (next to the handbrake).

location of converter

To find out if they are fitted, you need to remove the black trim from around the base of the ‘B’ pillar and see if the 3 sockets in the photo below are present:

location of converter


Battery connection

The large connector with the red and black wires is the feed from the vehicle battery. It’s connected to a dedicated 50 amp midi fuses on the battery positive terminal (so is permanently ‘live’). The Fiat Converter’s Manual rate this connection as ‘max constant current 53A’.

I used this socket as a supply to our 30 amp battery-to-battery charger.

The mating plug (MTA 45.40400) is already fitted to the connector, but isn’t supplied with any contacts. (Press the clip and the two halves of the connector will separate.) You will need to find two contacts, part number MTA 1707685. (I found them on ebay with the description  “TERMINAL KONTAKT VON MACHT MĂ„NNLICH MTA 1707685 AUTO CAMPER MOTORRAD AUTOMOBIL” – note that you will need two).

Once you have separated the two halves of the connector, the contact retainer unclips from the back of the plug:

contact retainer clip

The contacts

contacts and retainer clip

The contacts soldered to wires, insulated with heat shrink and ready to fit to the connector housing. Note that I’ve marked the + and – sides (on the masking tape) from the red and black wires fitted to the van side of the connector.


The terminals slide into slots in the connector

fitting the terminals

They’re held in by the yellow clip:

fitting the terminal retainer clip

If everything is assembled correctly, the clip will latch home.

assembled connector

The other side:

termials in the assembled connector


The 15 way connector

The following information is what I could find for the current X290 series of vans. Colour codes aren’t necessarily consistent from year to year, or from manufacturer to manufacturer, so proceed with caution and satisfy yourselves that you’ve identified the correct pins.

The 15 way connector functions are described in the Fiat Converter’s Manual (X290 version):

15 way cconnector functions

The mating connector for this socket isn’t supplied – it’s a Tyco ‘Mate’n’Lock’ 15 way plug part number 1-480710-0. You will also need some male connector pins to suit. Again, these are easily available from ebay

To confuse matters, there seem to be two different ways that the sockets have been numbered.

The Converter’s Manual shows the numbering as three columns of 5:

connector pin-out as shown in the manual

This was *not* how our van was wired. By tracing the wiring colours and doing some tests, I found that the table above was still correct, but that the pin numbering was arranged as five rows of three:

correct pin numbering for our van

Check your socket carefully, as there’s no guarantee that Fiat et al haven’t come up with another way of numbering things in the meantime. The wiring colour codes are Italian, I think:

Fiat wiring colours

This is the rear of the socket in our van (a 2018 Relay) showing the wiring colours:

wiring colours on a 2018 relay

‘Key ON’ / B+ Signal

The “Key ON” signal is straightforward to get to on pin 13 – the two blue wires in the photo below. Note that this is only really intended for electronic signaling or powering a maximum of two relays.

Key+ connection

D+ / Charging Signal

The D+ (‘Charging’) signal is not as straightforward: Pin 2 of the connector actually goes to ground when the alternator is charging, rather than to 12V like a true D+ signal.

In order to generate a true D+ signal it is necessary to wire a relay into the circuit: Relay pin 86 should be connected to pin 13 of the converter’s socket (+12V supply with limited current – suitable for 2 relays / 600mA max). Relay pin 85 should go to pin 2 of the converter’s socket (active low D+ signal). It is a sensible precaution to use a relay with a built in protection diode to reduce the risk of damage to the ECU.

circuit for d+ signal from conversion interface

The fuse is just sized to protect the D+ wiring and supply any loads on the D+ circuit.

The 12V for the D+ signal could come from pin 13 of the converter’s socket too (connect relay pins 30 and 86) if the loads are very low, and you are confident that the total load on pin 13 won’t exceed Fiat’s 600mA limit.

Rear Speaker Connections

These are on the 6 way connector:

pin out for the rear speaker connector

The mating connector is a TYCO ‘Mate’n’Lock’ 6 way plug part number 1-480704-0 with male pins to suit. (ebay

Note that pin 1 is described as ’12V permanent power supply…’ – this is just a connection back to the dashboard so that an after-market radio could be supplied by 12V from the leisure batteries via this connector. I believe that the wiring at the radio connector also needs to be modified to use this connection. Fiat  do not allow this modification for the standard radio.

The stock ‘Uconnect’ radio may or may not have its rear channels enabled. Ours did, but the head unit also needs to sense a load on the speaker terminals to actually make the rear channel live.

As I just wanted to connect a subwoofer to the rear channels, I had to add dummy load resistors to the connector (you can see one in the Key+ picture above). I used 56 ohm, 3W wire-wound resistors, but I’m sure you could buy something suitable from a car audio shop.

There are various instructions on how to enable the rear channels, but this option may not be present. Even though it relates to the US Promaster van, the menus, etc. from page 7 onwards of this document (pdf) are present our head unit, but like I say, the rear channels were already enabled when we got the van.