A friend of mine bought a 92 formula and is having problems with the charging system on it. He bought a new battery and a new alternator for it (both have been tested good).. The car has a mess under the hood as far as wiring goes..

When he turns the car on, it is simply not charging.. Unfortunatly we've stared at it for a week and it seems like it is not going to be an easy fix. Where should we start to diagnose this problem? There is a crappy alarm hacked into alot of the wires and I guess it would be a good idea to get rid of that, but is there any way to wire up the "bare essentials" just to see if we can get it working right and then wire the accesories up from there?


Any help is much appreciated..

 

There isn't really anything inline that would keep the alt from charging the battery unless one of the 2 were bad which, you stated, is not the case.

The 3 wire alt should have +12v at the tan/white wire while the key in the 'run' position. If there's no power here, the regulator will not turn on (powered, whatever you want to call it). The brown wire runs to, I believe (don't take it as gospel though) the volt gauge or something (it wasn't even shown as present in a '91 service book I borrowed from the dealership) and the red wire goes to the large terminal on the starter and has a fusiable link (possiable blown ?). The terminal on the back of the alt. should have a heavy gauge wire running to straight to the battery.
If all that is hooked up properly, there shouldn't be any reason for the battery to not charge.

 

The brown wire is the sense line. It goes to a point in the fuse panel where maximum voltage drop occurs. This is to keep the average voltage in the vehicle around 13 volts or so. As DB stated the tan/white is key on 12 volts, and the sense wire should also read 12 volts or so. Assuming the heavy wire from the rear has continuity to the battery with these three things the alt should charge. To verify the fuse link is ok disconnect the battery and measure with a continuity tester or ohm meter from the red wire on the rear of the alt to the POSITIVE battery connector. Disconnect both battery connections when doing this test. I pulled a Chilton and on a 88 model the sense goes to the fuse for the blower motor and it is labled chg-fan. On a 1990 it shows the line going to the fan fuse also, but is simply labled fan. Both fuses are 20 amp. Hope this helps.