Re: [DMCForum] Idle thermistor

["Walter Coe" <Whalt@xxxxxxx>]

I have been contemplating modifying the way my car looks at
the idle thermistor.  I do this EVERY time I sit at a light,
have to shift my automatic into neutral and rev up the
throttle.  The problem is, as with probably all DeLoreans,
is that the alternators do not put out enough at low RPM to
generate useful current while the radiator fans & other
items are depleting the battery.

One obvious answer is to change out the radiator fans with
something more efficient.  I've done this on another
DeLorean, and it has made an enormous improvement.  Total
cost was about $75 for a pair of 12" pancake fans & related
hardware.

But still I want to do more.  I would like to modify the
idle thermistor circuit so that it changes idle speed
according to system voltage as well as coolant temperature.
A very simple way to do it is to just have the feed for the
aircon compressor and/or radiator fans activate a relay to
put a resistance in series with the thermistor.  But it
would be more elegant to have a feedback loop adjusting this
resistance according to system voltage.  And what would make
it really sweet is if it could self-adjust enough so that
the RPMs increase enough to get the alternator making power
at idle without revving the sloshbox while my foot is on the
brake.

Can anyone suggest such a circuit?  I'm a good repair tech
but a lousy engineer when it comes to stuff like that.

Until or unless I can make something like that work, it
looks like the best alternative is to install more efficient
radiator fans and find yet a better alternator.  John
Hervey's alternators are a good try, but I have never seen
one work as well at low RPM as an OEM Motorola that has a
good working regulator.  I have had two of his alternators
on my car.  The first one went bad.  I sent it back to him,
and he lost it.  The second one he accused me of not paying
for (cash deal at a car show).  Two years later I
reluctantly installed it, and it failed because an internal
spacer was missing.  The friction caused plastic to melt
which contaminated the brushes causing failure in about 3
hours.  Do I send it back to him and risk having him loose
it again?  Or risk having him say that I didn't pay for it
to begin with?  Oh, the politics...

Walt    Tampa, Florida

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