Since your alternator isn't charging at all, there are two possibilities:

1) The alternator is bad. This isn't as strange as it sounds, I went through three newly rebuilt alternators before finding a good one. Many of these cores are now beyond saving, and competent rebuilders are a dying breed. I don't care if it says Bosch on the box. Bosch rebuilds nothing, contracts out the work, and the name alone is not a guarantee of satisfaction.

2) The alternator isn't getting D+ voltage. Does the cluster light glow when you turn the key to the on position? If not, it may be as simple as the bulb being bad. It may not be intuitively obvious, but the indicator light is a key part of the circuit. If the bulb doesn't glow at all, then the alternator may never start charging. On some of these cars, there are alternative paths supplying D+ to the alternator, but on others, the bulb is critical and a burned out bulb will disable the alternator. If you have a test port on the right inner fender (see photos), it's easy to check D+. Just make sure you have voltage between the D+ post and ground when the switch is "on" but the engine not running.

http://www.peachparts.com/shopforum/attachments/diesel-discussion/141479d1490225317-87-300d-no-tach-no-charging-no-idle-control-img_3170.jpg

http://www.peachparts.com/shopforum/attachments/diesel-discussion/141480d1490225324-87-300d-no-tach-no-charging-no-idle-control-img_3169.jpg