I have searched and searched again. Can someone please post a wiring diagram for the 1986 Volvo 740 and if you have the 1990 diagram post it as well. It should be in the back of the Haynes Manual.

Iwas having a next to impossible time finding the 1990 tail light so I decided to convert them to the earlier style but I need the diagrams to figure it out. Thanks

 

the haynes wiring diagrams are AWFUL.

what you WANT is the Volvo 740 greenbook wiring diagrams for the specific year. I only have greenbooks for 240's and 940's (including 1991 and 1992 740).

If I was in your place, I do believe I'd use an ohm meter to sort out the wiring of the two tail lights.

 

Try this link.
May help you out.
Volvo Wiring Diagrams

 

This is something I scanned in years ago. It's the whole green book diagram for my car. The taillights should not have changed much. Mine is an 89. I compared it to the 88 one too and it looks mostly the same. The taillights look identical.

https://onedrive.live.com/redir?resi...t=photo%2c.gif

 

The damn thing blows my mind. I had them mounted and was going through testing them. I had my back up lights working just fine. I went to sort the turn signals and when I had indicated either left or right my back up lights flashed. I said screw it and made my post. On both lefts there is 8 wires and on both rights there is 6 wires. You would thnk it is straight forward.