All you need is a simple digital volt meter to test an alternator on your car. First check the voltage with the engine not running and all electrical loads off (doors closed, lights off, etc). The v (from now on, v = voltage) should be atleast 12.5 v. Now switch on the ignition with out starting the engine. Make sure the battery light comes on. This is the most missed item when testing a charging system. The battery light MUST work, and if it doesn't it may not charge when started. Start the engine with everything else still off. V should be 13.5 to 14.5 v. Now turn on the A/C with fan on high, headlights on, doors open, but not the wipers (they cause very irregular loads on the system making it hard to get a good reading). V should be above 12.5 at idle and increase to 13.5 or more with engine at 2000 RPM. If all the above is OK, then your charging system and battery are OK. No fancy meters needed. This may not tell the maximun power output of the alternator, but will tell you if it has enough to keep the car happy, and that is all that matters.
There are a lot more things that can be checked with this very simple meter. For instance, make sure the battery is fully charged and with the car off, check the V. It should be 12.5 or more. Now turn on the headlights only with engine still off. If the V drops below 12 V with in a few min, then the battery is weak and needs to be replaced before it leaves you stranded. If the readings while charging with a load are low, switch the v meter to AC volts. If you see more than 1 V AC then the rectifier pack in the alt is bad. Back to DC Volts, if the readings very greatly say 12 to 13 v back to 12 when nothing else is changing, then the brushes are probably worn out. In this case replace the regulator which includes the brushes.
Another thing you can check for is bad grounds. Connect the - lead to the battery - term and the + lead to the engine. Start the car and watch the meter. If you see more than 1 v, you have a bad ground connection at the engine or a bad ground cable. If all is good, move the lead from the engine to the body. Now you have the + lead hooked to the body and the - lead hooked to the - post on the battery. Turn on the head lights and check the meter. If it is more than 1 v you have a bad ground to the body. Start cleaning connections until you can get it below 1 v , the lower the better.
The volt meter is a great tool when working on autos.

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84 500 SEL (307,xxx miles)