From voicebox@netcom.com Tue Dec 5 08:40 PST 1995 Received: from mailer by fshpp1 with SMTP (1.38.193.4/16.2) id AA18586; Tue, 5 Dec 1995 08:40:43 -0800 Return-Path: Received: from netcom2.netcom.com by UG.EDS.COM (PMDF V4.3-10 #4) id <01HYFXBYOVFK005JLB@UG.EDS.COM>; Tue, 05 Dec 1995 08:37:40 -0700 (PDT) Received: from [192.0.2.1] by netcom2.netcom.com (8.6.12/Netcom) id IAA14278; Tue, 5 Dec 1995 08:35:31 -0800 Date: Tue, 05 Dec 1995 08:35:31 -0800 From: voicebox@netcom.com (Dave C) Subject: Archive contribution To: jan@UG.EDS.COM Message-Id: <199512051635.IAA14278@netcom2.netcom.com> X-Envelope-To: JAN@FSHPP1 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7BIT Status: RO Jan: Here's a fix to a glowing alternator light on A1 cars where the alternator, regulator, and battery all seem to be good: The alternator light on my '79 Scirocco glowed when I turned on several high current appliances (400 watts worth of quartz-halogen headlamps, heater fan, rear window defroster). I thought that I was exceeding my alternator's output (only a stock 55-amp Bosch unit). When I had the opportunity to get a 90-amp alternator at a good price, I installed it, and replaced the cables with 8ga. cables (pos and neg) and good terminal ends connecting right to the battery terminals. But the alternator light still glowed when I turned on lots of stuff. Charge voltage was very good (13.97 volts). So I whipped out my multimeter and checked the current flow in the alternator light circuit (little blue wire going to the alternator). The current was flowing BACKWARD (from normal). It seems that due to some small resistance build-up in the fuse panel, the voltage at the alternator exceeded (when all the high-current devices are on) the voltage in the fuse panel where the alternator light connects. And Voila! the light glowed. So the possible solutions were: 1) Replace the fuse panel ($100++) 2) Tear apart the fuse panel and its connectors and clean everything and/or replace all the wire ends that plug onto the fuse panel 3) Stop the reverse current flow in the alternator light circuit I chose door #3. I bought a rectifier diode at the electronics store (1 amp, 50 volt, minimum) for 50 cents and plugged it in the alternator light circuit (use spade crimp connectors). I connected it right behind the left headlight where the blue wire splices into the wiring harness. Make sure the "cathode" end of the diode (this end usually has a band or other marking) goes toward the alternator. If you get it backward, the light won't light with the key on and the engine stopped. Just turn the diode around and try it again. With the ignition switch on, engine stopped, the light still lights brightly, just like it should. All appliances on, engine about 2000 rpm, it is totally dark, just like it should be. The only possible down side is that if the alternator starts dying slowly, putting out lower and lower voltage, the light won't light as soon as it should. But if the alternator or regulator quit altogether, the light will still let you know. This is a small risk I'm willing to take. This solution should work for any car that uses a light bulb as the alternator indicator (not late-model VWs; they use LEDs and shouldn't have this problem in the first place). Enjoy, Dave From voicebox@netcom.com Wed Dec 6 07:27 PST 1995 Received: from mailer by fshpp1 with SMTP (1.38.193.4/16.2) id AA09898; Wed, 6 Dec 1995 07:27:44 -0800 Return-Path: Received: from netcom2.netcom.com by UG.EDS.COM (PMDF V4.3-10 #4) id <01HYH92TSP7K005BP5@UG.EDS.COM>; Wed, 06 Dec 1995 07:24:42 -0700 (PDT) Received: from [192.0.2.1] by netcom2.netcom.com (8.6.12/Netcom) id HAA09390; Wed, 6 Dec 1995 07:22:31 -0800 Date: Wed, 06 Dec 1995 07:22:31 -0800 From: voicebox@netcom.com (Dave C) Subject: Re: Archive contribution To: Jan Vandenbrande Message-Id: <199512061522.HAA09390@netcom2.netcom.com> X-Envelope-To: JAN@FSHPP1 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7BIT Status: RO >Clever trick. I wonder though whether that wire serves any other >useful purposes that now may be defeated? I thought that that wire >is also used to in conjunction with the voltage regulator, >though I may be wrong. The only two functions it serves are: 1) to let you know when voltage at the alternator drops below voltage at the battery (well, actually, at the fuse panel). With the diode, the light won't light until the voltages differ by more than 0.7 volts. But since most alternators or regulators die catastrophically, the light will still report these failures. 2) to put an "exciter" voltage to the alternator once the alternator starts to turn (when you start the engine). I measured the charge voltage with the engine running (about 13.97 volts) and disconnected the alternator light wire. The charge voltage didn't change. I don't understand every detail about how this works, but it does. Enjoy, Dave