Voltage and alternator replacement

[Guest]

This is just a FYI, especially if you are chasing electrical gremlins. I experienced failure of the charging system a couple of days ago in heavy rains. This was probably a coincidence, but as the voltage dropped while driving I lost one system after another, headlights, wipers, instrument cluster, climate control etc...It only took a couple of miles to drop far enough for the ignition system or fuel pump to quit, which of course killed the car. In this case I discovered the nut on the output stud on the rear of the alternator was slightly loose, causing the plastic insulator around it to melt slightly. I replaced the alternator just to be on the safe side even though the present one tested okay (125 amps @ 12.4 volts) as it has 93k on it. The reason for the post is the difference the new alternator made. Since the charging system is back to where it should be, the car starts more quickly, the windows operate faster and even the remote door locks have more range. The bar graph gauge on the car never gave any indication of trouble, as it always ran in the center (as it still does), until the voltage started to drop and the electrical error came up on the IPC. Since the battery only carried the electrical load for about ten minutes or so, it was obviously not fully charged before this incident occured, yet there was no real indication of trouble up until the failure. <P>------------------<BR>Hal, btk@vbe.com

[Guest]

<P> Alternators generate a 3 phase AC current that is rectified to DC by six diodes<BR>(electrical check valves). If one of these diodes fails, the regulator boosts the output on the remaining circuits, and the failure might go unnoticed. What does happen is that the DC coming out of the alternator is extremely "noisey". This plays hell with anything which communicates digitally, such as the powertrain control, dashboard, AC control etc. <BR> The only way to detect this kind of failure to to do a sophisticated full load test on the alternator, or to look at its output with an occiloscope. <BR> If we start experiancing gremlins which come and go, or are too stange to explain, this might be an area to check into. <BR>

[Guest]

I know what you mean by the diode failure, the big alternator on my winter car, Taurus with electric windshield, failed last year and it made the most awful whining sound, both in the radio and audibly on the outside of the car.<P>------------------<BR>Hal, btk@vbe.com