Greg Mayman wrote in a message to Roy J. Tellason:

 -=> Roy J. Tellason said to Greg Mayman
 -=> about "VEHICLE LED'S" on 09-25-03  04:06.....

 RJT> I've thought that this might be the case,  but wasn't sure.  And
 RJT> although I do have some wiring diagrams,  none of them were handy.

 GM> I don't have ANY wiring diagrams, not even for my current
 GM> vehicles. I'm just going on what I've seen over the years, and
 GM> unfortunately my memory of how these things were set up is a bit
 GM> hazy...

 RJT> Before the vehicles I had that had this solid-state stuff I had one
 RJT> that used a single-coil relay.  It was apparently supposed to operate
 RJT> at a fairly high rate,  between two sets of contacts or in between. 

 GM> Yes, I still have one of those regulators. It was used on most DC
 GM> generators. An early form of pulse width modulation of the 
 GM> generator field. I don't recall ever seeing it on alternators, but
 GM> it could have been used -- it would work just as well on a rotating
 GM> field as on a fixed one.

The car I'm thinking of was a 1967 Plymouth Fury.  I'm pretty sure it had
an alternator...

Not until you mentioned it did I think about the fact that earlier stuff
used generators.  I mean,  I knew that,  but just hadn't considered it at
all since it's been so darn long since I've seen a vehicle that used one. 
Sorta like six volt batteries,  I guess.  :-)

 RJT> The damn thing let my battery keep on running down until I bent the tab
 RJT> that held the spring for that contact a bit,  forcing the issue
 RJT> somewhat.  I can also remember earlier stuff yet,  going back to the
 RJT> sixties or thereabouts,  that had three coils in there.

 GM> Yes, there was the "cutout" that connected the output of the 
 GM> generator to the battery once the generator had reached a high 
 GM> enough voltage. It had a second winding in series with the output 
 GM> that was supposed to cancel out the field of the voltage winding 
 GM> when the generator stopped and current flowed back into it. When
 GM> you think about it, a heavy duty diode would have done the job
 GM> almost as well, and a lot more reliably.

Except that heavy-duty diodes were neither widely available nor cheap
compared to coils and such back in those days.  I guess most of what
semiconductors were out there were germanium parts.

 GM> There was the second relay that was the voltage regulator that 
 GM> "buzzed" at a fairly high rate to control the current in the field.
 GM> Sometimes this had a second current winding to limit the output
 GM> current, sometimes this was done with a third relay.

 RJT> I hate it when they do that!  Reminds me of the Ford stuff we had with
 RJT> their ignition modules...

 GM> Yep. It keeps up sales of replacement parts.

Or something.

 GM> About 10-15 years ago, one of the electronic magazines over here 
 GM> carried a story from someone whose engine control computer had 
 GM> died. he was told it cost $1200 to replace it -- that tells you how
 GM> long ago it was.

I've never had a problem with that sort of stuff,  so far.  We did have
this one car which had a failure in some "module",  a stupid
Caddy that we ended up with because we were given it,  and which we were
happy to get rid of.  The darn thing had no heat!  And there were *four*
different modules involved in that mess,  according to what I could find in
the information I had available.  No clue as to which one had the problem, 
nor funds to just "throw at it" until it was fixed.  Was still
that way when we got rid of that car.

 GM> Anyway, he demanded that the old one be returned to him, and 
 GM> actually had to threaten legal action to get it!. He took it home
 GM> and carefully opened the sealed case. He found a PCB with a few ICs
 GM> and other components, with the identification removed from all of
 GM> them!

I've occasionally seen stuff like that -- chips with the numbers removed, 
etc.  I get *so* tired of people with the "proprietary" crap
ideas,  they keep trying this stuff over and over again,  and it never
works long-term,  but they use it for whatever short-term advantage they
can get out of it.

 GM> One component that looked like an electrolytic bypass capacitor had
 GM> burst its case. He unsoldered it and put in a cap from his junk box
 GM> of a size that he thought would probably do the job. When he tried
 GM> the computer in his car, it worked perfectly!

Heh.

 GM> But most interesting was the label he found INSIDE the case that
 GM> showed it was an old one that had been reconditioned by Bosch
 GM> Electronics -- and this had been fitted in his NEW car!

That almost sounds actionable to me.

 GM> No wonder the makers didn't want outsiders to be able to repair 
 GM> them!!!

Sometimes it's a matter of their arrangement.  We've all heard about some
of the "agreements" that m$ has with computer sellers,  etc.  I
knew a guy who worked for an outfit that dealt with a lot of car radios. 
They had to spend a *LOT* of money for special environmental test chambers,
 so that they could deal with Delco stuff.  After a repair it was supposed
to be put through a fairly rigorous bit of testing,  I guess.  Anyhow,  I
was doing some car radios a number of years ago,  and was occasionally able
to borrow schematics from this guy.  But not Delco stuff.  Even though
there wasn't really much of anything proprietary in there (they did put
their own part numbers on stuff), he said that if they got wind of any of
that info leaving the place they could lose their franchise to work on the
stuff...

Gotta keep people "locked in",  I guess.

 RJT> I don't think it's much heavier than that,  though I could find out
 RJT> when I get my hands on those wiring diagrams.  And it's not like it's
 RJT> carrying that current continuously.  The ammeter in the truck is
 RJT> actually marked with a "40" at each end,  and it's
*very* seldom I've
 RJT> ever seen it go the whole way over,  and then only for a fairly short
 RJT> period of time. 

 GM> Yes, that's right. The leads usually aren't very long as the 
 GM> battery is usually near the alternator. And 5000A/squ.inch isn't
 GM> all that heavy, certainly not when that is only reached 
 GM> occasionally.

Thinking about it,  the battery is on the driver's side,  and the
alternator isn't.  Same thing holds true for my car,  which has a
sideways-fitted V-6 in it,  the alternator is at the rear of the engine
compartment,  diagonally opposite the battery's position.  Not sure about
our other car offhand.

 RJT> Yeah,  it depends on where I end up putting that second battery.  If I

 GM> That's always a problem in modern vehicles.

That truck ain't what I'd call a "modern vehicle".  :-)  It's a 1978...

 RJT> Maybe if I'm lucky I can find a diesel truck in the junkyard and get
 RJT> the second battery tray and such from that...

 GM> Get a heavy plastic tray or storage box or similar to hold the
 GM> battery, from one of the cheap shops. Then all you need is a
 GM> bracket to support it or clamp it down as necessary.

I have some battery boxes,  but there's really no convenient way to mount
one of those,  they're more for marine uses.  And a tray,  same thing --
I'd have to figure out stuff with brackets and whatnot,  if I can find one
that was already made for that body style of truck (which covers a number
of years,  unlike cars changing a lot from one year to the next),  then
I'll find it a lot easier job.

 GM> One of my friends had his second battery (for his mobile amateur
 GM> transceiver) in the boot (trunk) of his car in a plastic storage
 GM> box that I think was vented outside with a plastic hose.

Venting really isn't a major concern,  overall.  I could stick it in the
bed of the truck in a box,  if I wanted to fasten it back there somehow and
have it taking up the space,  but then I'd need to run more wire.  And
since I figure that the charging current will be typically a lot higher
than the load current,  I'm thinking that the engine compartment is
probably the best place for it.

 GM> You really need something to protect the surrounding metalwork from
 GM> the acid fumes etc unless it is a sealed battery.

Even non-sealed batteries are pretty specific about where they're vented, 
and those don't do much in the way of venting acid unless you over-fill
them.  Excepting situations like what happened when my regulator lost its
ground connection,  that is.  I'd *still* like to do something better with
that,  maybe I'll drill a small hole right next to it and put sheet metal
screws with toothed washers there to ensure I have a good ground,  or
something of that sort...

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