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Date:         Fri, 16 Oct 1998 08:08:01 -0700
Reply-To:     YauMan Chan <YauMan@CCHEM.BERKELEY.EDU>
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         YauMan Chan <YauMan@CCHEM.BERKELEY.EDU>
Subject:      Re: Alternator warning light
Comments: To: earlsmit@ISLANDNET.COM, vanagon@VANAGON.COM
Content-Type: text/plain; charset=US-ASCII

Earl,

When an LED comes out of the LED stamping machine, the longer leg is the anode and the short is the cathode. But when it get installed, they are clipped... so there is no easy way to tell. But fear not. LED cannot be destroyed if you put in it backward.. it just won't light up. Just turn it around and it will work again. If you want to test it first, you can use an ohmeter. Measure the resistance one way, and then reverse the leads and measure again. The "forward" direction is the low resistence configuration. remember which leg had the red lead from the ohmmeter.. that's the leg that should be positive.

Caution. If you don't have an ohmmeter, and wants to test which way to light up, don't just connect it to a battery. It will survive a reverse direction, ie no light up direction, but in the corrrect forward direction (light up) there will be too much current and may blow the led. LED circuits have current limiting resisters so it is much safer to test the LED in circuit rather than putting it across a battery unless you put something like a 2K ohm resister in series.

Yau-Man Chan 87 GL

>>> Earl Smith <earlsmit@ISLANDNET.COM> 10/15 7:34 PM >>> Is there any discussion in the archives about how this system is supposed to operate? Hayes manual is careful to point out that the LED has a negative and positive terminal but nowhere does it tell one which SOCKET is positive or negative.

Earl from Sunny Sooke 84 ex-California Vanagon


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