Hello Thomas
I shall help you to mount your Veglia clocks. I did it on my 309 Vital some time ago, and if I remember your 309 Graffic has definitely the same engine than mine.
First I want to apologize because my pictures are a bit blurry. So here's our first picture of the clocks where everything is connected and fully working.
Here is a picture of the wiring loom when the steering wheel and the surround plastics have been removed.
You can see 4 connectors on the picture above. A yellow 8-pin connector, a blue 7-pin connector, a green 9-pin connector and finally a white 10-pin connector. It is on the latter connector you must work to connect the oil temperature indicator as well as the oil pressure indicator.
Here is a photograph of the white connector, the order of wires goes from right to left (!!!).
As you can see from the picture, the first one is not used. The second wire is where you must connect the oil pressure sensor so the indicator will work. On the same connector, use the seventh pin to connect the oil temperature sensor.
Here is a picture of the connector pins you need to use.
You can buy them in your nearest Peugeot dealer (ask for part nb. 6540.92). They should still be available.
Here is another picture which shows the back and front of the oil pressure sensor. It's used on 309 SR / SRI / GTI / GTI16.
And then here are two pictures of the tee adaptor which you can use to fix the oil pressure sensor and the oil pressure sensor. You can directly screw it in where the original oil pressure sensor goes. So, just replace it. I bought this tee on eBay.
An overview of my car's engine bay.
On the following picture you can see the wiring loom that goes to the clocks. It's the one with the red wire you can see on picture 2.
On the following picture they also distinguish the place above the filter where they can use the oil temperature sensor. There should be a cap which is exactly the same as the oil drain plug.
Here is the wiring diagram you need.
I hope that the information I provided will be useful to you. Please don't hesitate to ask me your questions.
Best wishes,
Malik/Vital76