Hello,
I am hoping that the wealth of knowledge on this website can help me to diagnose what is going on and how to fix it and if I need to replace the alternator.
The symptoms:
1. If I drive without any electrical load (except for the ignition & the fuel pump), the charging light can't be seen coming on (actually it does very slightly and can be seen if I pull the light from the instrument panel)
2. If I drive with some load, like the headlight or the heater fan or the A/C motor on, the charging light comes on, the more the load the brighter.
I know most of you will tell me that the alternator is not charging the battery causing the more load the brighter the light. However, when I did some checking the voltage on the alternator (B+) and the blue wire terminal (D+) I am not too sure if that is the case.
As you know the reason the charging light comes on is if there is a difference in voltage between the alternator (B+) and the blue wire terminal (D+), so I did some voltage checking at the alternator at different RPM and loads and this is what I found out
<colgroup><col span="5" width="65" /></colgroup>| RPM | Alt (B+) w/o load | Alt (B+) with load | D+ w/o load | D+ w/load |
| idle-1000 | 14.4 | 12.6 | 16.5 | 17 |
| 1500 | 14.6 | 13.17 | 16.9 | 19.5 |
| 2000 | 14.6 | 14.2 | 17.5 | 20.5 |
| 2500 | more or less the same as at 2000 RPM | |||
If I check the voltage for B+ on the battery, it is a little bit less but it is less than even 1 volt.
What this is showing me is that the D+ (blue wire terminal) voltage goes way up and the difference with alternator voltage is causing the light to come on. Also you can see that the difference in voltage between B+ andD+ with load is also bigger than without load between the 2 terminals causing the light to come on brighter.
Any idea what is going on? Should I replace the alternator? If I don't need to replace the alternator how do I make the charging light not to come on?
I need the power of knowledge and experience here.
Thanks all