Hi all, Cannot troubleshoot this myself.
2004 V70 2.4 N/A Auto, 63,000.
Rear wiper motor does not operate; also do not have the lights above the rear license plate. Fuse is good, have 12v to both sides of fuse. No voltage at the connectors near the r. wiper motor. Inspected the wires at the hatch hinge - great shape.
Here's a puzzle: license light 2-pin connector, two black wires on one pin seem to be the ground wires. Resistance to ground <1ohm. Gray wire on that connector - no voltage & infinite resistance to ground. Three pin connector to wiper motor has yellow, white & black wires. The white wire had <1ohm resistance to ground. The Yellow and black wires were open to ground.
A black wire as ground and a white wire as ground in the same bundle does not seem right? ?
One more clue: I can hear a relay click somewhere in the back from the drivers seat when I switch the rear wiper on - either full on or intermittant.
I would like to run power straight from the battery to test the wiper motor. Which pin gets 12v + and which pin should be ground?
Thanks for your help.
Dennis
Spokane WA

 

Well, the white wire could very well be ground. They make these different colors so you can trace the wire all the way through the harness when troubleshooting. I suppose they have two separate ground wires because not all cars have the rear window wiper? If I had a schematic right now I'd be able to tell you how to test the motor for sure. But I wouldn't connect 12v straight to the yellow or black wires until you know for sure. Most likely they are for CW and CCW though.

Try this: Put the wiper on intermittent and crawl around back there until you can find the relay that you hear clicking. Attempt to find out what wires are going to the relay and measure signal levels from there. Are you familiar with relays? Most likely the 12v coming from the fuse will power the coil on the relay, then the contacts on the relay will control power to the motor. I'll bet the normally open contact is for CW and the normally closed contact is for CCW or visa versa. The power will be cycled to the relay, which will in turn rotate it back and forth.

Good luck!

 

According to my 2002 V70 wiring diagram the wire colors match your description and your measurements for the license plate lights make sense but the wiper motor white wire measurement doesn’t look right.

For the wiper motor and according to my wiring diagram the white wire is the intermittent wiper motor power and the yellow wire is constant wiper power line, black is ground. Not sure why you’re seeing <1 ohm on the white wire, this is what doesn’t look right to me. The white wire goes directly to the wiper motor and you may see a low resistive value through the motor to ground but less then 1 ohm doesn’t look right especially since you’re also seeing an open on the black ground wire. This is a long shot but if the white and black were broken in the wiring harness they could short together, the white wire could be touching the black ground wire at the break.

If your taillights are working the license plate lights should also be working, same power circuit, only the wire from the license plate lights through the tailgate wiring harness and up through the left hinge area can be the problem if you’re not seeing power at the license plate lights.

These problems really do sound like a problem with the tailgate wiring so I would check the left hinge area again, be sure and pull the wiring harness cover back far enough to check for broken wires on both sides of the hinge area.

 

Thanks for the suggestions. Have family events to attend this week. Hope to get back to this Friday or Saturday.

Dennis

 

Ahh, the hinge area, sounds like an opportunity for a smashed wire to me.

 

So what's the status? These forums help more when a solution is posted.

 

Looked deeper into the wire loom and found many broken/pinched wires.
The breaks were 3 -4 inches down inside the main body - not in the rear hatch. Found by carefully slicing the loom. Really looks more like a pinching problem, not a numerous flexing issue. Trying to remember how many wires are bundled together. Seems like 10-12 wires. All were damaged except 1.
To repair you should have on hand soldring iron and shrink tubing (my opinion).
I now have power to the motor & lights. Three wires to motor: black is ground; yellow is 12v constant; white is 12v from switch - either on or intermittent.
I do not have an operational wiper yet. Have a short inside the wiper motor. Looking for a replacement. Seems to be about $200.00.
Thanks to all for your help. I had read about the wires breaking, but they seemed good at the hinge. Needed to dig a bit deeper.

Dennis

 

I am glad you were able to find it. You definately had the symptoms of shorted wires. Are you certain the motor is shorted internally? Check the resistance across the motor coil directly with it disconnected from the circuit. Call Volvo if you need to, they should have a specification. Don't be surprised if it is only a few ohms. I can measure mine and send you the results if you need to. You can also test it by directly applying power from the battery (conveniently located in the back of the vehicle) according to the schematic.

Also, visit http://www.uneedapart.com/ to find a used one in your area. It should save you a bit. I personally have never seen a wiper motor fail. Chances are this one only failed (assuming it did) because of the smashed wires. Therefore a used one is just as good as a new one.