i have a 1990 740 glue 16valve, had the local tech shop put alternator in for me, now battery will not charge, lights work, no alternator light, but looks like some funking wiring with some black tape behind alternator, is this bad. Is there a problem with using an aftermarket alternator to replace the original. help.....when I boost the car to start it .........it runs great while jumper cables hooked up.......as I take them off I can tell that engine looses power.........can anyone tell me what is going on........by the way when I get in the car.......will run at high rpm's ......2-3k without problem....then when idles.........it flutters and dies........is this the juice....in the wires......or the juice to carb........can anyone help

 

Hey, gman, it sounds like your alternator is no good. If the car doesn't run well - or at all - if there's no other car attached to it, there is something wrong with your charging system.
If you have a meter that will display voltage, put the leads on the battery and see what the voltage is when the car is running and when it is off. An alternator, if running properly, should put out 14.4 volts or thereabouts. A battery should put out 12 volts or less if under load (i.e. if the car is running and the alternator isn't working).
Electrical tape on the back of the alternator isn't neccessarily bad - if the connections are okay and there is no leakege, it okay - as a temporary measure.
Hope this helps.