Your voltage may be running a bit low. The battery or the voltage regulator might be the problem in addition to cabling issues. From the Pocket Data book, measured at the back of the alt between battery B+ and the D- ground terminal, the Volvo spec at 2500 rpm for the later alts is 13.8V-14.6V on the car with a minimal battery load and 14.1V-14.9V on the bench with no load. More commonly you'd expect to see closer to 14.25V at the alt, a bit less with loads on or a charging battery, a bit less still if measured at the battery posts (cable/connection voltage drop). I usually want to see around 13.25V-14.25V measured at the battery at >1700 rpm with minimum loads and no less than 12.5V with all loads on and a battery in only average condition.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now