1990 245 DL - Tailgate Wiring Blues

I just scored a righteous 245 from a fellow TBer. It's a '90 DL, LH3.1, M47 non ABS car. I love the wagon, its a righteous hoopdi! But my plan is to import it to Canada with me when I move next year, and I am fairly sure export control for U.S. and Canada will want to make sure all indicator lights are in working order (Would love to talk with anyone who has experience with this!). Now, I dont want to have to part this car because I really like it, and it has a story, and I got this as a project not a daily and Im not a quitter!

Here is my current dilemma:

The tailgate that came with the car was a leaky nightmare. So I recently swapped on a nice 90+ tailgate in working order I got from a fellow tBer (sup billy780, thanks again!), with all new OEM Volvo tailgate wiring harnesses on both sides, new bulbs and a new wiper motor.

On the new tail, the only lights working are the licence plate bulbs, nothing else - no 3rd brake, no wiper, no degfog. I suspect the bulb failure relay and rear wiper relay may be partially at fault - I have both and will replace and see if it does anything, hopefully I will have good news! As for the defog, I think some deeper wiring gremlins may be at play that will require some troubleshooting.

If deeper wire surgery will be needed, especially if I need to check grounds (which I suspect may also be a culprit), I could really use some tips on how to go about it. I have a wiring diagram and multimeter ready and figured I would see if any fellow tBers had any best practices to share, considering this is quite a common 240 problem. I have never attempted such electrical troubleshooting before and could use all the advice I can get

This is my first time attempting such electrical diagnoses, my diagram and Bentley manual are helpful, but of course nothing beats comparing user experiences.

Anyone deal with this before?

As always, insights are greatly appreciated!

-Serge

There is a ground strap in the hinge on both sides. I don't think it's included in the repair kit. You need to add one in the mix.

57plymouth said:

There is a ground strap in the hinge on both sides. I don't think it's included in the repair kit. You need to add one in the mix.

Click to expand...

I do a diy repair of these grounds by drilling a small hole on each side of the hinge. Then you can use some small screws to hold a ring terminal at the end of the new ground wires inside the hinge. Takes up less space than trying to connect the old broken wires back together. You need flexible fine strand wire if you can find some. I use a teflon insulated fine strand 18 gauge I have around.

To test just temporarily run a jumper wire or something from a good ground to the metal of the tailgate and see if stuff starts working... You can use your multi meter to test from any ground point (say the ground for the 3rd brake light, or the ground on the wiper motor) to a body ground. If you see no continuity you have deduced in a scientific way that your tailgate lacks ground... If the wires are indeed hooked up right, then a bad ground is very likely the issue. And like I told you earlier, I've only ever had issues with the wiring for that stuff back there, never any problems with the relays in my experience anyway...

I would also test voltage at the 3rd brake light, and the wiper, while using a good body ground on the other side of your meter. This will show you if you are getting voltage to the required places or not. Of course you are going to want a helper to hit the brake, and turn the wipers on and off while you look at the meter...