-=> 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.

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

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

 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.

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

There was the second relay that was the voltage regulator that
"buzzed" at a fairly high rate to control the current in the
field. Sometimes this had a second current winding to limit the
output 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...

Yep. It keeps up sales of replacement parts.

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

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

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

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

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

 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. 

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

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

That's always a problem in modern vehicles.

 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...

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

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

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

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... The first rule of intelligent tinkering:  Save all the parts!
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