Hi guys, hope eveyrone is having a good Sunday.

I picked up an Innova multimeter to measure dwell on the cars. Not sure what is normal behavior but it has a reading BEFORE I connected it to anything, meaning when I turned it on it was reading around 90 despite NOT being connected to anything.

When I connected it to the car (red to - coil terminal and black to ground) I got a steady 69.5 reading.

The 69.5 reading is a bit high but in the right range, but not sure how much I trust it given that I would have thought the meter would read zero when it was powered on but not connected to a signal.

Anyone have a digital meter they use that could confirm normal/expected behavior of these things?

Thanks!

Anyone able to comment on whether the 12 m will have a nonzero reading when it’s not yet connected?

Thanks!

http://dtec.net.au/Ignition%20Coil%20Dwell%20Calibration.htm

You should have spent the money on a set of Petronix and never again need to set dwell or replace the points.

Ha, and not a bad consideration but then I wouldn’t have been forced to learn anything new.

Mark - Thanks for the article but I didn’t see if it covered the behavior of the meter itself, sorry if I missed that. I’m basically asking if I can trust the meter.

Even with bosch points and blue coil dwell was rarely an issue. New Bosch points, condenser and test the coil... pretty simple.

One thing that can mess you up is the point gap. they tend to close a bit after tightening the set screw.
Try an .018" feeler then recheck the gap, often you end up with the .016" needed.

If you have a powered dwell meter red to positive black to negative batt terminals and the small lead to the negative side of the coil. Then turn the engine over and if the dwell is correct it should read 50 on the four cylinder scale. If just two leads on the meter, (dwell tach only) then black to negative and small lead to neg side of the coil. We like the simple dwell meters (unless setting the dwell on 914-6 with electronic ignition) with the two leads and the needle that will wiggle to the left and right of 50 as the car is turned over, so we can adjust the points gap while reading dwell

Thanks for all of the information and discussion, I certainly understand well now, which was kind of the point.

Back to part of my question-this is what the Multi meter is reading even without anything connected, maybe that’s just how it’s designed but it seems odd Click to view attachment

On 4cyl dwell scale:
90 deg dwell is points closed all the time.
0 deg dwell would be points open all the time.
45 deg dwell would be the points closed half the time and open half the time.

Any dwell reading without being connected to a running engine is meaningless.
The 90 degree static reading would seem to just be "no voltage" at the probe = points close all the time.

PS I don't remember if my DVOM has a dwell scale, it has been that long since I set points.

Jim

Thanks Jim - super helpful.

Just check the other ‘74 and it measured exactly 50.5 on a car wall that was well tuned (advance was bang on as well) so it appears to be working.

Thanks again for the education gentlemen, appreciate all the responses!