

| Subject: | Re: Two warning lights come on TOGETHER |
| From: | George Goff |
| Date: | Tue, 23 Aug 2005 10:53:35 EDT |
In a message dated 8/23/05 9:09:37 AM, eduntz@HOTMAIL.COM writes: << I can troubleshoot for the alt and Oxy lights, but why would they always flash on TOGETHER? >> You need new brushes in your alternator. The warning lights flicker because the brushes have yet to totally queef out. In order to have a bulb check function before the engine starts (and before the alternator begins to do its thing), the idiot lights for the alternator and the OXS are connected together by a diode on the low side. If all things are kosher whenever the alternator is spinning, the diode is reverse biased and the OXS warning light is not lit unless, of course, the elapsed mileage has been achieved. If the alternator fails or its output voltage becomes low (usually due to worn brushes making weak contact with their slip rings), the diode will be forward biased because the battery voltage will at times be higher than the alternator voltage. Then, the OXS warning light and the alternator light will glow to one degree or another. George
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