Hi there,

Yes, the gray wire is supposed to get battery from the relay when you turn the wipers on, but the black gets battery whenever the ignition is on regardless of the wiper swich or whether you have the intermittent feature. The black wire does the parking, and to hear you've seen it cycle merely by closing the tailgate is only strange if all the wires, including the ground jumper, are indeed intact on the right hinge.

If simply tightening a ground doesn't fix it, trace that gray wire back to the "S" terminal (armature) of the relay down by the driver's left foot. The relay itself is in a bad spot for moisture, stomping, etc. But on the face of it, I would have gone in the same direction you had, with the tailgate hinge wiring.
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Art Benstein near Baltimore

A man's knowledge can never outweigh his experience.

there is a ground connection to the tailgate frame for this motor which can appear sound but gets corroded. remove it sand it and the frame it sits on and reconnect.

Howdy,

I think you may have binding mechanical linkage. Disassemble, clean, lube, and reassemble.

Here is a NEW link to the polish web site with the Volvo wiring diagrams:
http://www.volviki.org/tiki-file_galleries.php

The old link (http://volvo.techno.org.pl/wiring-diagrams.html) will redirect you close but you have to struggle through (unless you read Polish) to find the page with all the drawings.

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Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 52 year old fat man. ;-)