Freq valve?: [urq] My multimeter has frequency % duty not dwell -can

[Buchholz, Steven]

... since all you are trying to do is to verify the functionality of an
ECU you shouldn't need to worry about conversion ... you can verify the
dwell with both ECUs ... and if they are similar the new ECU is probably
good.  One other test you may want to try on both ECUs as a test is to
trip the WOT switch manually while the engine is idling.  This is a
diagnostic function that forces the duty cycle to 50% ... you should
verify that both ECUs behave similarly in this mode too.  

... just saw the other posts too ... just to be clear ... dwell *is* a
valid measurement ... it is another measurement of duty cycle, defined
in a way which was established for measuring the duty cycle of points
calibrated for the number of cylinders in the engine.  Frequency is
*not* what you want to be measuring ... I would expect the frequency to
remain somewhat constant, but can't say for sure as I've never measured
it ... 

Steve B
San Jose, CA (USA)
> >
> > This relates to me trying to test this used MAC-02 ECU
> > I bought.  I figured by testing the dwell (hum - this
> > is probably the dwell on the frequency valve)  I could
> > tell if the 02 sensor loop on this unknown ECU works.
> > SO I was going to measure dwell with the cars current
> > ECU which seems to work great - and then plug in the
> > purchased MAC-02 and see if I can tell if the 02
> > sensor loop is working at all.
> 
> Duty cycle is what you want to be reading.  I have read about 
> measuring
> dwell, but that must be converted to a % duty cycle anyway by 
> dividing by
> 90.   I have some crappy craftsman meter that I use for duty 
> cycle that
> measures frequency on the same setting, just push a little 
> gray button on
> top to choose between those or something like that, I think I 
> remember the
> frequency to be something around 3 or 6kHz.  Maybe you've got the same
> meter.