Measuring ignition coil resistance

[Dale_W]

The engine is on a 2004 Yamaha Raptor 660 ATV. Ran fine for many years. Now, no spark.
The coil was very accessible, and the manual gave instruction on how to measure with an ohm-meter.
The primary coil is measured from the base (ground) of the coil to a terminal opposite the spark plug lead. It should be 0.18 to 0.28 ohms at 68 degrees F.
The secondary coil is measured from the terminal to the spark plug lead. It should be 6.32 to 9.48 K ohms at 68 degrees F.

I forget if it was the primary or secondary, but one of them was an open circuit.

I am using my Klein MM700 multimeter.

So in comes the new coil. I measure this new coil and find the primary to fluctuate between .2 and .3 ohms.
Close enough.
But the secondary, terminal to spark plug lead is crazy. The meter fluctuates like crazy and eventually settled in (more or less) around 2.5 K ohms. (too low)

I often visit www.raptorforum.com (ha more often than I like) for help on this ATV.
There are a few moderators over there that are really good. Of course the coil question comes up.
The mods over there insist the ‘meter can’t accurately measure down at the less than 1 ohm area.’

Is this why the meter jumps around so much? If so, I thought my new Klein would be up to the task.

The ATV is about 2:30 away. We’ll bring up the new coil and give it a try in a two weeks.

Any thoughts or comment on measuring the resistance of the coil?

Thanks

Dale

[Arkie]

I suspect you are good to install and test the new coil.

Some auto ranging DMM's (Digital Multi Meters) will keep changing auto readings somewhat. (going up and down at high resistances before a DMM finally settles is just one of several reasons why I usually reach for a analog ohmmeter.

If the meter were mine I would go ahead and test a know resistance such as a 10 k resistor for example or use another meter.
But in your case you did find the old coil bad and the new one getting a reading and also Onan for example has changed the ohms specs reading on their new coils and the new coils will actually check out of specs for the OLD specs in the service manual.

AND most generally in this neck of the woods electrical or electronic parts cannot be returned for a refund anyway even if new and not ever used. (unless is apparent that the parts dealers made a obvious mistake and got the wrong part)

[KE4AVB]

I too don't like the auto-ranging meters. I prefer one that has different resistance scales and does looks like I am going get myself a Simpson 260 meter. But normally the auto ranging on my current doesn't flop around too much so it is livable.

[Dale_W]

Thanks guys. I pulled out a really really old Radio Shack analog multi-meter and gave it a go on the new coil. Much easier to use.

I also put the alligator clips on the digital multimeter, clipped them on, and just let it sit.
It did calm down quickly, and with no human movement, gave readings very close to the analog meter.

Next time we visit the cabin we'll install the new coil. I expect to report back that all is well.

Thank you for the input.

[Arkie]

Since the rig is 2 1/2 hours away,

you might do little reviewing to see if you are suppose to read a pulsing voltage on the neg post of the NEW coil if you do not get a run. (especially if you do not have the Raptor's Yamaha SERVICE in hand readily available when looking at the machine)

Not sure of the Raptor but some Yamaha ATV Service manuals mentions to test for pulsing voltage from the pick-up coil or CDI if NEW ignition coil is not firing.

[Dale_W]

Just an update.
I have not yet taken Arkies advice on the pulsing signal. May not have to.

Re-installed old ignition coil. No spark. Disconnected the plug from the voltage regulator/rectifier. Plenty of spark now.

Here is the thing. With the VR unplugged, she'll start and run every time.
With it plugged in, It might give spark and run, or it might not. Towed it all the way home because of no spark with the VR plugged in.
Get it home. It runs with the VR plugged in.
An hour later, no spark with it plugged in.
Next morning, runs with the VR plugged in.

Here is another tidbit: A while ago I had started a thread here about my ATV and regulator/rectifier. I ended up replacing mine and all is well.

We ran thru the same diagnostics on this ATV. Everything is pointing to the VR being bad.

Biggest clue is 12.8 volts DC at the battery with the engine off, and 12.5 vdc with it running. Even when revving engine.
With engine off, all 3 wires coming out of stator coil have .6 ohms resistance. (When measuring wire 1&2, 1&3 and 2&3)
With engine running meter set to volts AC, the same combinations give 24 vac at idle, and 35 vac when revving.


So we'll order up a new VR.

Question at this point is, could the VR be intermittent on killing the engine, or letting it run, even tho it will not charge the battery?

Thanks, Dale