I have a 1986 764T which I have owned nearly 8 years. Last spring I replaced the wiper blades with Bosch MicroEdge, and then the trouble started. The wipers would be jerky, and sometimes stop or get stuck. It sounded to me like the motor was wearing out and couldn't operate against the increased resistance of the new wiper blades, so the local Volvo repair shop replaced the motor with a good used one (they even said at the time that wiper motors don't usually go bad on 7xx's). The problem is no better. Perhaps 30% they will get stuck before moving, 40% they will move and get stuck mid sweep, 20% they will operate ok but jerky and sluggish, and 10% they will operate almost normally. When the problem did not get better after the replaced motor, the shop banged around and gave it a temporary fix. A few months later I took the cowl off and removed the assembly, which I cleaned and lubed with wd40. It seemed better for a couple of days, but I still have the problem. The senior mechanic who no longer works on cars but rather runs the business thought he remembered something like an intermittent relay causing a problem like this on these models. I also have considered maybe a bad ground wire or similar? When the wiper gets stuck, it doesn't drag on the power (no change on alternator gauge) so that makes me think it might be electrical. Also, in theory, the motor is fine, since it was just replaced. But why would the problem start when I replaced the wiper blades, when they had worked fine up until then?
I have come to realize that problems are rarely isolated occurrences; that others with the same model may have encountered similar problems. Has anyone had a problem like this? This car is my "rainy day" and winter driver, so wipers are an important feature! I realize this isn't click and clack, but PLEASE if you have any experience with a problem like this let me know. I am stumped.
Thanks in advance, Patrick Kentucky, USA