Trailer lights being weird

[Dave79]

Hi. So l bought a 2011 ex AA swb transit. Good order, seems like it'll last. Thing is, it's got a 13 pin trailer socket, so I'm using a 13 to 7 pin adapter for my caravan.

The red lights and brakes are fine.
The indicators are not working when it's all plugged together, nor the hazards.

When indicator stalk is used a relay (that sounds like it's in the fuel tank)is clicking like mad. There's also a high pitched ring coming from somewhere too.

Any ideas lads? I'm working away from home for a few weeks and I'm due to take the caravan with me on Monday night. Having indicators would be a bonus.

Cheers in advance

[roviw]

Sometimes instead of having a warning light on the dashboard there is a ringer or beeper in the wiring in the rear of the vehicle to say that the indicators are flashing.
I bought a new trailer a couple of years ago and it came with a 13 pin plug. My van and jeep had a 7 pin socket so I also bought an adaptor. The adaptor used to play up though and sometimes not work correctly and it also meant two joints for damp to penetrate.
In the end I cut the new plug off and put another 7 pin plug on to replace it, not a problem since then.
Might it be worth removing your old 7 pin plug from the caravan and changing it for a 13 pin new one ?
Should come with instructions as to which colour wires go where.