[T3] tach calibration

Bryon Garvin spinningrooves at gmail.com
Fri Jun 22 11:37:59 PDT 2012


A few weeks ago (a month?), Jim mentioned that he calibrated his tach/dwell
meter or mentioned that you should check to make sure it is correct.  How
do you do this?

I have a rather old-looking Actron meter that tests dwell, RPM and some
other tests.  I don't believe I ever saw a calibration section in the
manual (which I do have somewhere).  The unit seems to be sealed and not
adjustable from the outside.  If I get it open, is there likely a
calibration pot on the inside that I might find?  And if so, would I just
set the rpm to equal what the tach says, for instance, on my 96 Jetta when
it's running?

My meter is so old, without taking a picture of it...I have trouble even
locating an image online.  But this is pretty much it:
http://thumbs4.picclick.com/pict/3007257880594040_/Actron-Model-No-612-Vintage.jpg

Sorry for the small picture.  But you get the idea of how old it is.

Any calibration suggestions are welcome!  BTW, the reason I am asking is
because I was working on my Jetta and I was trying to hold the rpms at 2500
for a bit.  I was using the meter to read RPM while standing at the engine.
 Later, I thought "I should check this against the car".  That's when I
noticed it was reading low for what the car said on the instrument cluster.
 If it's wrong, this leads me to believe I have been setting my idle
incorrectly in the Fastback.  However, it runs pretty well so it can't be
that far off.

Thanks,

 - Bryon, '71 Fastback MT/FI
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