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Post by Deleted on Mar 12, 2018 10:05:16 GMT -5
I recently got a coil from a member here on HOH to help me out with a saw I'm trying to revive.I've read that a good coil should test between 7 & 8 ohms.When I tested the coil that was sent to me it tested 8.8 ohms.The coil came off a C-71.Any thoughts here?
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Post by Deleted on Mar 12, 2018 12:19:05 GMT -5
It’s most likely good
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Post by brushy on Mar 12, 2018 20:08:06 GMT -5
I recently got a coil from a member here on HOH to help me out with a saw I'm trying to revive.I've read that a good coil should test between 7 & 8 ohms.When I tested the coil that was sent to me it tested 8.8 ohms.The coil came off a C-71.Any thoughts here? What setting did you have your ohmmeter at? |
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Post by undee70ss on Mar 12, 2018 20:22:58 GMT -5
Unless your using a certified calibrated meter, there is some variation In readings. I would just try using the coil.
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Post by Deleted on Mar 12, 2018 22:57:44 GMT -5
I guess all multi-meters are different.The one I used has a setting on it for ohms,that was it,just ohms.I can take a pic of it & show you.
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Post by sweepleader on Mar 13, 2018 6:39:22 GMT -5
My experience has been that a very special (read expensive, very expensive) meter is needed to be accurate in that low ohm range. A meter might read tenths of an ohm but unless it cost over a thousand dollars, plus or minus 1 or two ohms is as close as it will really get. It might be consistent so checking 10 coils would show the one bad one or the one good one but comparing readings to specifications can be troublesome.
I would go with undee's advice, the only sure way is to put it in a saw and see if it runs.
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Post by Deleted on Mar 13, 2018 7:53:15 GMT -5
This is a coil that I got,along with a rear handle & complete airbox for my XP-1000.It's going to be awhile before I can get to working on that saw,I have too many more important saws to work on right now,plus my upcoming hand surgery will put me way behind.That might take 6 mo.to get function back again.
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Post by brushy on Mar 14, 2018 12:44:15 GMT -5
I guess all multi-meters are different.The one I used has a setting on it for ohms,that was it,just ohms.I can take a pic of it & show you. All the videos and posts on the web( not this site) said to set the meter to 20k ohms. I’m just curious if that’s why my readings are between 2.9 and 4.0, and here the lucky number is 8. I haven’t been able to reach 8 with any setting on my meter. |
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Post by Deleted on Mar 14, 2018 14:25:22 GMT -5
As luck would have it I just took a pic of my meter about 5 min.ago.Here it is:  20180314_151102 by edju1958, on Flickr |
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Post by sweepleader on Mar 14, 2018 14:37:09 GMT -5
The reading will depend on the meter setting. The meter will put out a small voltage, usually around 1.5 volts for a "normal" multimeter or VOM (Volt, Ohm, Multimeter) or DVM (Digital, Volt, Multimeter). If your meter only has one ohm scale and nothing else it would normally be referred to as just an ohm meter. When changing scales for different readings, many DVM's need to be rezeroed because the internals of the meter are different and with only 1.5 volts to work with, things have to be set just right. If a test calls for a 20K ohm scale, it is trying to account for some of the variables in meters and the task at hand.
All of this relates to my comments about not trying to get an exact number, down to the ohm, with a common meter. They will not all read the same. They will normally repeat well enough to compare two test parts with the same meter. Electronic circuits are tough too because they may have active components that change resistance over short periods of time. Ignition modules would possibly fall into this group, simple transformers or coils would not.
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Post by sweepleader on Mar 14, 2018 14:43:11 GMT -5
As luck would have it I just took a pic of my meter about 5 min.ago.Here it is: That looks like an autoranging meter, very high impedance input, probably fairly accurate. I would guess that the range button on the left upper is a range select which would be used to lock the meter on the 20K range for this test. Usually they do not have a zero adjust, you would just touch the leads together and note the reading, adding or subtracting it from the test reading. I would still not count on it to measure a resistance of 8 ohms closer than a couple either way. |
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Post by jerseyhighlander on Mar 14, 2018 14:49:22 GMT -5
What Sweepleader said, in both posts.
If you were to take six of those same meters, new out of a box, they would probably all read differently side by side. They just don't have that tight of a working tolerance until you are getting up to really expensive meters. Even the expensive ones, need to be calibrated once in a while. The other question, forgive me if it's been said already, how well off is the battery in the meter?
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Post by Deleted on Mar 14, 2018 15:00:33 GMT -5
OK,that explains the results I got on a module that I posted in another thread in "Ignition Systems"A friend of mine found this meter in the garbage at a farmer's house that he does work for.He said that this meter is about $80.I have no idea.
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Post by Deleted on Mar 14, 2018 15:07:43 GMT -5
As far as I know the battery is new,or relatively new.
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Post by jerseyhighlander on Mar 14, 2018 15:09:35 GMT -5
Another factor that can help make you nuts... When testing resistance, get reading then press the probes in harder and it will change. Especially in the autoranging digital meters, your reading can be all over the place depending on how hard you press. I really prefer the old analog meters for resistance testing.
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Post by Deleted on Mar 14, 2018 15:32:11 GMT -5
I have an analog meter that I bought last month,unfortunately I don't have a battery to put in it to test.A friend of mine just happened by with this one & he was kind enough to let me use it.I think it's been accurate enough for anything I need.I tested a coil on the old XP-1000 & it tested at 2.2,which tells me it's dead.Most likely that's why they quit running the saw.When it came to replacing anything electronic back in the '60's people,especially old timers,freaked out.Now a coil for the Xp-1000 probably cost around $20,give or take a couple bucks.Ms Joyce could be more exact with these figures.The XP-1000 was made for only one yr.,from 1965 -1966.I happen to remember those days very well.A person could go buy a used running,in good condition chainsaw for $10-$20.I know this because my dad did (and it was a monster Remington).So if a person could go buy a whole running chainsaw for $20,why would they spend the same amount of money for only one part?We do the same thing today,it;s a disposable society we live in nowadaysI'm sure that I'll have everyone on the forum argue these points with me.I'm just stating my opinion.
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