91 940se hacked wiring help Topic is solved

rickbrk · Post by **rickbrk** » 24 Jan 2021, 15:19

I recently got this 91 940se and have been going through it. The diagnostic plug doesn't work so I went to the junk yard and found a better one. I went to wire it in and notices someone had cut the blue wire that goes to the led and wired it to a green\red stripe wire that goes to a smaller relay in the pic below. They also cut a blue\pink wire that seems to go to an empty spot in the smaller relay socket. Does anyone know what the smaller relay and socket go to and what the green\red wire goes to?

lummert · Post by **lummert** » 25 Jan 2021, 10:42

You need to locate the wiring diagram for a 1990 Volvo 760.

rickbrk · Post by **rickbrk** » 25 Jan 2021, 18:48

So I traced down the wires going to the mystery relay. 30 goes direct to positive battery terminal. 86 goes to a chassis ground. 87 goes to terminal 15 on the coil.. 85 goes to the blue wire that powers the led in the on board diagnostic plug. If I remove the hella relay the car will not start. Plug it back in, it starts. If I put the blue wire back into the diagnostic port, it doesn't start. So a constant hot and ground and I'm assuming the blue wire is hot when key is on and a wire to the coil. Could they be supplying power to the coil from another direction? Cause it won't start if the hella relay is removed.

rickbrk · Post by **rickbrk** » 26 Jan 2021, 17:51

The voltage to the coil is around 9 volts. The relay they put in supplies the full 12 volts to the coil. But I can't find where the resistance is coming from.

rickbrk · Post by **rickbrk** » 28 Jan 2021, 15:55

Solved... I was checking voltage at the coil and the radio suppression relay and noticed if I bumped the rsr the voltage at the coil would change. For some 5\32 female bullet connectors and had to modify them to fit the relay then siliconed them in place at the back of the connector. Now no voltage drop, mystery relay removed and I can use my diagnostic port also. Now to fix the exhaust leak at the manifold and it should be good to go for a while. I've only had this car about a month and really starting to like it. Thanks for everyone's help in figuring this out.