

| Subject: | Re: two red lights aren't on at start |
| From: | MOST,DAVID |
| Date: | Wed, 10 Jan 2001 19:54:30 -0800 |
Given your explanation below (thanks) and that I haven't check anything yet, could the oxygen sensor be responsible for the symptoms? While checking another problem the other day, I started the the engine with the oxs disconnected. I then connected it while the engine was running (though I only disconnected and connected the two wire plug and not the single wire lead). I don't notice any new running problems. Thanks again, David On Wed, 10 Jan 2001, David Beierl wrote: > At 10:17 PM 1/10/2001, Bill Davidson wrote: > >But wouldn't the alternator light come on after starting if it wasn't > >charging? ... he said that it doesn't come on at all... I assume that means > >after starting also... > > No, it wouldn't. The alternator needs a tickler circuit to get it started > -- that's the D+ terminal which must be supplied with a small 12v current > to begin charging, and which then itself supplies 12v while the alternator > is charging. > > Having the dual need of a startup circuit and also a warning light for the > alternator, the auto-makers combined the two -- when the alternator is > drawing through the D+ terminal the light is on, and when it's supplying > voltage there the light goes out. The current through an LED isn't enough > to trigger the alternator, so VW also put a resistor in parallel with the > LED through which most of the current flows -- might be 150 ma or something > like it. > > Then because they also needed a lamp test for the OXS light (and safety > belt light, I think?) they hooked those into the circuit as well, using > diodes to isolate them. And oh yes, they use it to drive the relay to > power the fridge when the alternator *is* charging. > > If the alternator light doesn't light with ignition on, it's one of three > things: bad LED (happens, but you can win lots of money betting against > it), bad 12v supply to the panel (which ought to affect other things on the > panel), or the other end of the circuit isn't being properly grounded > through the alternator -- busted wire, unplugged wire, bad connection at > the panel plug, bad alternator. But regardless, if it doesn't light with > the motor off it won't light with the motor on either. > > david > > > >Bill > > David Beierl - Providence, RI > http://pws.prserv.net/synergy/Vanagon/ > '84 Westy "Dutiful Passage" > '85 GL "Poor Relation" >
Have something to add on this topic today? Revive this thread in the forum »