I recently had to change out the dash board in the '95 850 and when I put everything back together the windshield wipers started working intermittently. During the troubleshooting process I found the connector close to the ww motor was kinda boogered up. I put it back together making sure I had a good metal to metal contact and everything is fine now.
I have attached a picture of what I found.

 

Those rubber insulators always break down they are such a pain.. If you check you main relay on top of the radiator and your plug to the ABS module as well as some other plugs you will find the same issue.
I usually pull the plugs apart one lead at a time, and replace that failing insulation with some Tygon fuel hose.. Not that that is the best thing to use but its what I had laying around and seems to work perfectly.

 

you know I never thought of using rubber hose as repair for the old disintegrated rubber connectors. I just cleaned off all excess rubber, connected the male and female, electrical taped every mm of plug, and hoped for the best.

Has been almost 6 months since i've rigged that plug (right side of the upper intercooler hose, above the radiator)

Now i'll know if that fails, i'll use the extra silicone vacuum hose I have in the rear seatback.

 

Volvo sells wires to repair the plugs for pretty cheap. I think they are a couple of dollars and it is the connector with the rubber on it.

 

i use 5 minute epoxy and a small peice of metal - first i clean the plugs and make sure they are the correct way around when i put them back in the socket and then i open the little flap at the bottom of the socket and fill it with epoxy - making sure that the plugs are all the way in before the epoxy sets then after it starts to harden i snap the bottom of the plastic socket back into place-- voila ---------and it waterproofs the back side of the socket