Rear tow bar electrics. What is this for?

[sgould]

While removing the CD changer today, I noticed an odd "relay" on top of the LH wheel arch.  Only 2 of the three pins were connected, so I can't see it working as a relay.  The two wires are Red/Blue and Black.  No spare connector floating about that could have fallen off.

It's connected to the towbar "add-on" unit that I think deals with the indicators, but it has been installed in an odd way.  The towbar unit is in the rear RH corner of the boot, under the floor.  The two wires are wrapped in their own loom, but this wire has been run across the rear of the boot and up to the top of the left hand wheel arch, for what appears to be no real reason.  Half way along, the wiring has been bundled up and cable tied.  If unwound there would be about 15 feet of wire.  Is it some form of "beeper" that should be in the front of the car? If so, when does it beep?





The coil of unneeded wire




And the end of the wire

[sgould]

Looks just like this bit of kit.  Part No. 400106316

But the blurb refers to a warning light that illuminates when a trailer indicator lights fail.  So, I suspect that the spare terminal may be a signal to do this, but it was never connected.  Or the "relay" is just a way of providing a load to disable the output.

[Audax]

But the blurb refers to a warning light that illuminates when a trailer indicator lights fail. 

Ah-ha! I think I now know what the mystery warning light I have on my dash is, it's a genuine Saab part fitted below the heated seat controls in a switch port. I always figured it was to do with the tow bar but never investigated precisely what.

[Norfolk Jim]

I have that on mine and it's goes to a small green light on dash in place of one of those dummy blanks and is for trailer light fail system

[phoenix]

Yes, it's definitely the wires that should connect to the warning light that is to be installed on the dash, which is to show that the trailer indicators are working. Why it has a relay instead of a lamp is odd.

The relay box takes 12V in and the relays within drive (I think as there are 3 relays) the indicators and brake lights to avoid upsetting the filament monitor.