0.25 Volts AC from stator. But ohms out ok. What to check?

[777funk]

My Force 50HP Stator coil should read around 750 ohms resistance which it does, and no continuity to engine ground. However when cranking, I'm only getting around 0.25 Volts AC from the two blue wires. I have the Pre-D model (1987). I believe I should be getting around 200VAC with a multimeter so that tells me a problem related to the stator or magnets.

Could the magnets come off or uncharged? From what I can tell, I have a thin ring of ceramic magnets around the inside perimeter of the flywheel. A screwdriver will not hold here but will faintly stick. OK or not, I'm not sure. So most likely a bad stator? I also tried unplugging at the rectifier.

 

[Jiggz]

In one of your previous post you stated you measured 300VAC on the stator. So what changed? Or it could be that you initially measured with a hand held os-scope and this time measuring with a regular DVM? Measuring voltage on the stator and trigger requires a DVA adapter to get the correct readings. Here's a link to a more specific t/shooting steps with the ignition system.
Ignition Troubleshooting

 

[777funk]

In one of your previous post you stated you measured 300VAC on the stator. So what changed? Or it could be that you initially measured with a hand held os-scope and this time measuring with a regular DVM? Measuring voltage on the stator and trigger requires a DVA adapter to get the correct readings. Here's a link to a more specific t/shooting steps with the ignition system.
Ignition Troubleshooting

Either the stator has failed since then or more likely I was not seeing the decimal point when taking the original measurement with the multimeter on the stator. Even without a DVA, I should be able to see a reasonable amount of AC coming through I'd think since the stator generates pretty high voltages.

 

[Jiggz]

With good resistance reading it could also be broken strands on the blue leads connecting to the windings. Eventually, I believe you would have to pull the flywheel and do a systematic inspection of both the magnets, trigger and stator. DO NOT USE THE TWO OR THREE CLAWS/ARMS GEAR PULLER as these puts tension on the sides of the flywheel and could easily crack the flywheel. Use the three bolt holes around the shaft and use high grade 5 or 8 bolts and a balancer puller instead.

 

[jerryjerry05]

You using a DVA or peak reading volt meter?
NO, then you won't get the right readings.
A stator can test good but still be bad.

 

[777funk]

You using a DVA or peak reading volt meter?
NO, then you won't get the right readings.
A stator can test good but still be bad.

Wouldn't the AC setting on a regular multimeter give a close reading to what the stator is putting out? I realize the trigger is putting out a pretty low voltage pulse, but the stator is generating 200+ VAC if in spec. I would think that would show up at least close with a regular multimeter wouldn't it? I will say this is the first time I've ever messed with a stator so I don't know much about testing them.

 

[Jiggz]

You are correct that you should at least have some kind of voltage readings even without a DVA adapter on a regular multimeter. However, remember the stated 200 VAC is a peak reading (which you can achieve with a DVA) and not the RMS. But for sure you should read way more than 0.25 VAC. So there is an issue with the stator. Personally, I would get a cheap DVA just to be sure before replacing a more expensive stator and of course for future uses too.

 

[Nordin]

If you are handy you can build your own DVA adapter.
Google DVA adapter and the schematics will show up.
I have made a couple of DVA adapters myself.
It is a diod, a capacitor and a resistor. Really simple to build and the DVA adapters purpose is to store the peak voltage from the stator in the capacitor so the VOM has time to show the voltage value. It is actually showing the peak DC voltage cause the stator puts out AC voltage.
Cause it is as jiggz says, the regular VOM can not handle to show the peak value, it is showing the RMS (rot mean square) value when you measure AC voltage.

 

[jerryjerry05]

Ebay "DVA Adaptor"
Google "how to make a DVA adaptor"

 

[777funk]

Thread solved. Now have over 300 volts AC measured with a regular meter coming from the stator. The problem was that the magnet ring came unglued from inside my Prestolite flywheel. Epoxied it back in.

Already noted in my other thread but may as well note it here for future reference.

Also for reference, a meter measures around .1 vac or a little more (in circuit) from the trigger coils. I get 1 volt DC from my DVA adapter.And the engine runs well.

 

[Jiggz]

Finally! Congrats and enjoy.

 

[Nordin]

Good to hear it is up and running.
Please make a feed back to the forum on how long the gluing of the magnet last.
For example after a season or after 6 month or so.

 

[777funk]

Good to hear it is up and running.
Please make a feed back to the forum on how long the gluing of the magnet last.
For example after a season or after 6 month or so.

Sure... Good idea.

In my case, it's not going to really be a good example for someone else to follow since it was epoxy past the expiration date. I think it's about 10 years old. It was a good epoxy brand (West Systems 1 gallon kit with pumps), but the epoxy had gone bad with time. I watched the left over material for a couple days and it never hardened. It settled into a hard gel state. Usually it cures into something so hard I would have to drill into it. This cured into something I could cut with a utility knife fairly easily and pry the blob of left overs away from the edges of the glass jar I mixed it in with a screw driver.

But so far... it's staying. I'd doubt I could easily peel the magnet band out of the inside of the flywheel. If it fails, it'll be a pain to clean. I'd probably buy a new kit of epoxy and reglue if so.