True, but if you change the resistance in a circuit on these PCM's, such as
soldering incorrectly, using butt connectors (bad idea anyway) or just
taping up a splice....especially O2, MAP, or the MDS system, they can easily
go out of range and trip the MIL (or put it into Limp mode on transmissions
- even if you're only off my 1ohm). I've had to put coils and crank sensors
onto an oscilloscope to prove to a "Professional" A/V installer that their
system was causing cluster issues (resistance related on the signal for a
particular circuit).
I fully understand the resistors on LED's (been there myself on cab issues
with LED lighting) and the small range you have for error. Just make darn
sure you don't ground the signal circuit - PCM goes "bye bye".
- Bernd
-----Original Message-----
From: Steve Preston [mailto:steveophonic@yahoo.com]
Sent: Saturday, February 02, 2008 10:39 PM
To: dakota-truck@dakota-truck.net
Subject: RE: DML: RE: MDS "on" LED...
I didn't explain it well. Let me try again!
If you put a high resistance load across a power
source,you will not affect it as much. That's why
voltmeters have such a tiny affect on the voltage they
are measuring (VERY high resistance).
Sorry. Still can't write it the way I think it.
Steve P.
--- "Bernd D. Ratsch" <bernd@dodgetrucks.org> wrote:
>
> Why put a resistor on the LED...you want almost no
> resistance on the
> circuit.
>
> - Bernd
>
> -----Original Message-----
> From: Steve Preston [mailto:steveophonic@yahoo.com]
> Sent: Saturday, February 02, 2008 9:43 PM
> To: dakota-truck@dakota-truck.net
> Subject: Re: DML: RE: MDS "on" LED...
>
>
> Thank you Bernd!! :)
>
> I should go with a red LED,because it won't need as
> much current,but I like BLUE! If I feed it through a
> 1kohm resistor or higher,it should be a negligible
> draw,not enough to affect anything.
>
> Thanks!
>
> Steve P.
>
> --- "Bernd D. Ratsch" <bernd@dodgetrucks.org> wrote:
>
> >
> > You could tap into the MDS control circuit (C3
> > "Black" connector at PCM -
> > Pin #6: Brown/White Wire - MSD Solenoid #1) but
> I'm
> > not sure how the PCM
> > will react with a slight change in resistance on
> the
> > MDS control side. It's
> > not going to be activated in stop and go, city, or
> > short highway runs
> > though.
> >
> > - Bernd
> >
> > -----Original Message-----
> > From: Steve Preston
> [mailto:steveophonic@yahoo.com]
> > Sent: Saturday, February 02, 2008 8:31 PM
> > To: dakota-truck@dakota-truck.net
> > Subject: DML: MDS "on" LED...
> >
> >
> > Hey DML! Is it possible to find some source of
> > voltage,either 5V or 12V,that is present only when
> > the
> > MDS system is operational on a Hemi? Anybody know
> > where such a source might be easily found? I want
> to
> > tap into that with a resistor and bright blue LED
> to
> > mount on the dash,to let me know for sure when I'm
> > in
> > four cylinder mode.
> >
> > Thanks!
> >
> > Steve P.
> >
> >
> >
> >
>
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