Printable Version of Topic

Posted by: jim_hoyland Jun 22 2018, 09:16 AM

How can I use the multimeter to determine whether a coil is outing out a tach signal ?

Posted by: jcd914 Jun 22 2018, 09:31 AM

If the coil works there is a signal at the terminal on the coil.
The points or ignition module shuts off the current flow through the coil and it is the on/off flow of current that the tach reads.
Whether or not it is getting to your tach or whether it is correct for your tach would be the question.

You should be able to read it with a dwell meter, won't tell you the rpm but would verify a signal.

Jim

Posted by: 914forme Jun 22 2018, 10:40 AM

Some Multimeters have a tach function also.

If you want to "see" it, then oscilloscope is your best option. As it can be setup to show the wave as the field collapses and then re-establishes.

Or a 12v light hooked up to the terminal. I made a small LED trouble light with a 12v LED some long leads and an old BIC pen. That would work also, why do I like it, extremely small load when compared to the older incandescent lights. That makes it good to test low amperage circuits also.

BTW, You can spin this by hand the trick is to make sure nothing is in the combustion zone to cause the engine to catch and fire.

If you do it with the engine running, Even at 800 RPMs that little light will be flashing at 1600 times per minute. Or ~27 times a second average human can see 150 transitions per second. So you should be able to see the flashing of the light.

1600 flashes a second to Beats per minute and you would be invent a new genera of metal, Plaid Metal

Posted by: plays with cars Jun 22 2018, 09:39 PM

Sorry Stephen I'm in a contrary mood tonight (been on a plane all day). The light should flash at half engine speed, not double. So 400/min at 800rpm, not 1600/min.

Either way, your point is still valid: should be able to see and led flashing.

Posted by: 914forme Jun 23 2018, 05:15 PM

Not a problem, I get shit wrong all the time.

Posted by: 76-914 Jun 24 2018, 10:17 AM

Jim, IIRC there was a light on the back of that unit that would flash if it was connected correctly. Of course, I would need to read over the instructions again to verify.

Posted by: jim_hoyland Jun 24 2018, 01:01 PM

QUOTE(76-914 @ Jun 24 2018, 09:17 AM)

Jim, IIRC there was a light on the back of that unit that would flash if it was connected correctly. Of course, I would need to read over the instructions again to verify.