I need some help with an electrical issue on my 91 honda civic. The battery was dead Monday, had it checked and was found to be bad, then found the alternator was not charging, changed it too. The alternator was tested prior to installation and is working. I still can't get the car to charge correctly, only getting 12.84 on my multimeter. I have checked the wiring to the battery and it is good at .1 ohms. I did find that the black and yellow wire is reading 40 ohms to ground. and the white and blue wire is reading 60 ohms to ground. I have disconnected the ECM, and still getting the same readings. Does anyone know which wires on the ECM are ground wires, or does anyone have a diagram for where each of the ECU wires go?

 

Is the alternator belt possibly loose and slipping?

Does this circuit diagram for a 90 Civic help you?

 

I have the belt pretty tight, I have around 1/2 play like you would have on a v belt. It looks to me like the two wires(white/blue and black and yellow)going to the ecu are shorted together somewhere(think they are the voltage feedback wiring. I am getting 40-70 ohms between them. I disconnected the wires at the firewall connector and the wiring to the alternator cleared and read good now. So it has to be between the firewall connector and the ECU which I have disconnected.

 

Only the BLU wire sends signals to the ECU (ECU connector B, terminal B14).

In addition, the WHT/BLU wire coming from the voltage regulator is supposed to merge with the BLK/YEL wire, which connects to the ignition switch (see circuit diagram).