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Good stuff. Just to clarify, the minimum 0.2" is the distance the brush extends out of the holder without pulling on it, not the actual length of the brush. I culled the following out of some old notes in case anyone is interested.
As mentioned, for worn slip rings, you don't want heavy scoring or a wear groove (ridge on either side of where the brushes ride). The brushes can jump in and out of the groove indicated by a flickering alternator idiot light. Scoring will be evidenced by shortened brush life and lots af arcing. Sticking your finger inside the regulator mounting hole will soon confirm that -engine not running of course. I don't necessarily recommend it, but I've had success removing the ridging by turning the rotor in a drill (keep the other end in the alternator case clamped in a vise), filing it level with a bastard file (who named those anyway?) then polishing the slip rings smooth making sure there are no burrs or grit between the slip ring segments. Only takes a few minutes and you've got little to lose.
I'm notably cheap so I start by replacing just the brushes if they're getting short -typically the dash idiot light is starting to glow occasionally at night. Parts counters may not list brushes separately for your vehicle, so order for an older vehicle like an '82 240. Initially, if the light comes on intermittently bright then it could be worn brushes or a worn alternator (slip ring) or a poor electrical connection. For the early 83/84-86/87 240's with disintegrating wiring harnesses, a poor electrical connection can include crumbled insulation on the smaller red alternator wire (excitor) in the harness going under the front of the block, otherwise look for a poor connection at the terminals on the back of the alternator. As these problems get worse the idiot light may be glowing constantly. If the excitor wire is disintegrating, run a new wire from the block connector on the firewall along the firewall and down the fender. Use heat proof stove element wire (the kind with the cloth wrapping) available by the foot at many hardware stores. Use a solder splice at the connector block and use a nickel plated crimp terminal (not the cheap aluminum ones) at the alternator. Nickel plated terminal terminals can be found at appliance parts stores.
Otherwise, if the dash light glows persistently or the battery won't charge adequately then there are a number of cases:
o It could be that the alternator is not producing enough juice. Check this by measuring the output voltage at fast idle (1450+). Checking the output at the alternator is preferred, but at the battery should be just fine provided the primary voltage wiring and engine/chassis ground are okay. You should see at least 13.5 volts (should be more like 14.25 volts). If not, this will normally indicate a bad regulator, it can also indicate that one or more of the internal diodes in the alternator has fried, especially if the car has been recently jumpered off another vehicle and it was done incorrectly. Bad diodes used to be a common problem, but not so much any more.
o It could mean a bad battery. For an old battery it may simply lose its charge overnight. The idiot light will either not glow at all or will glow solid bright if the battery plates collapse internally and short out a cell. The simplest way to check this is to fully charge it disconnected from the vehicle then reconnect it and see if it can produce and hold a full 11.5-12.25 volts under a moderate electrical load (like fan on high plus park lights) with the ignition off. Check it again in about 8 hours if you're suspicious, but disconnect the battery in between in case there's a constant electrical drain you aren't aware of.
o Otherwise, start by replacing the regulator pack unless you suspect diode damage in which case you might want to take it into a local starter/alternator shop for testing and repair.
A local shop will usually rebuild an alternator with diodes and bushings for a very reasonable price if you can wait a day or two. They will often have access to Bosch regulators and brushes at non-Volvo prices. You can also buy these parts over the counter at many auto parts stores (like NAPA or Lordco). After that it's either buy a re-built unit with some kind of warranty (the starter/alternator shop will often have a good deal with a 90 day warranty) or off to the salvage yard for a used unit. The last stop is the Volvo parts department and that would typically be only for newer vehicles where there's no parts supply in the re-built chain or salvage yards. There is usually no need to upgrade to a higher output alternator unless you have increased the electrical load with accessories like a heavy duty lighting system or a massive sound system. If you want to upgrade something, buy a top end battery with a great warranty. If there is any doubt, either check the owner manual (many available on-line at the Volvo site) or a decent service manual to determine the original alternator rating -someone could have conceivably put in a lower rated alternator.
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