1913 Touring - MAG output test - Hmmmmmm

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Model T Ford Forum: Forum 2012: 1913 Touring - MAG output test - Hmmmmmm
Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare - Victoria Australia on Tuesday, April 17, 2012 - 06:09 pm:

I have done my magneto output test on a dial guage and followed it up with a digital type to see the variance, you know, l didn't see a lot of variance.

Guage - 11 volts at idle
Digital 11.6 volts " "

Guage - 33 volts at 3/4 Throttle
Digital - 31.9 volts " " "

Both of these measurements were taken while the car was running on battery.

Not taking it up any faster unloaded.....

At this stage l guess these figures are ok, what is the expected range for a new rebuild, with newly charged magnets ??

Cheers David.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Tuesday, April 17, 2012 - 06:29 pm:

Was there an 1156 bulb in parallel with your meter?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare - Victoria Australia on Tuesday, April 17, 2012 - 07:47 pm:

Uhmmm ....NO.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Wednesday, April 18, 2012 - 07:54 am:

With no load the readings are not valid. They could be valid if the readings are similar with a load. You really don't know anything until you measure with a load across the output.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Wednesday, April 18, 2012 - 09:34 am:

Do we need an 1156 bulb when the engine is running on mag.I don't think so.
Toon


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Wednesday, April 18, 2012 - 10:25 am:

Sorry , I mean , when I do some measurements with an Analoog meter.
Toon


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Wednesday, April 18, 2012 - 11:10 am:

Yes you do, to be sure the magneto readings are valid. Typically they read much higher without a load.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Wednesday, April 18, 2012 - 11:23 am:

Royce , When the engine is running on magneto there is a load of the coils , and that is what you need .


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, April 18, 2012 - 12:26 pm:

Anthonie Boer:

If you want a reliable reading rather than a "guestimate" then you need to take your readings with an analog meter using an 1156 as a load while running your car on Battery. In some instances you can get nearly the same reading using a digital meter but that does not make the meter then reliable for sure. The problem is that the T coils generate a ton of RF noise that digital meters tend to pick up. The amount they pick up is dependent on a lot of things that you cannot really control and no 2 digital meters are alike but all analog type meters are very repeatable in the way they work and are totally passive when reading AC volts. They can of course have been dropped or connect to a large overload and thus burned up some of the internal meter parts but assuming the analog meter is in good order it will be accurate enough for your use here. Using the coil as a load then adds the noise of the make/break of the coil primary as a make/break load on the magneto which gives a further "unknown" to what you are reading. The idea is not to measure the magneto in a way that might get you a false reading and to eliminate as many variables as possible so that we can all share notes. To get accurate input from the folks here you have to do the test the same as they have done it. The more variables you add to the mix the less likely you will get accurate advice. As others have stated - if you get the same analog meter readings again with an 1156 bulb as a load while running on Battery then your magneto is good.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, April 18, 2012 - 04:35 pm:

If any of you routinely do Model T Ford magneto testing you should consider obtaining a proper tool for the job.
By far the best test device available is the St Louis magneto tester made by FunProjects. This is precision instrument with a carefully selected reactance component that produces a constant voltage regardless of varying engine speed and frequency and voltage from the magneto. If it passes the St Louis test you for sure have a good magneto. No guessing.
Remember what Henry Ford said "if you need a tool and don't buy it soon you will have paid for it a don't have it".
Here is a link to St.Louis Magnet Tester
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Wednesday, April 18, 2012 - 07:28 pm:

Switch your ignition to mag and recheck your readings. You will also know if it runs well on Mag.
I am pretty certain your mag is just fine.

Owners have maintained these cars for nearly a 100 years now with a minimum of tools and equipment. I don't think you need to buy or have access to every tool the most well equipped dealer of 1925 might have.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, April 18, 2012 - 08:36 pm:

Ted
Perhaps you missed my point?
Sure, today's cheapo Model T crowd can save a dollar with inconclusive magneto tests and live with the conclusions.
My point was for those who work in Model T's for others and the operational word was "need". These guys need a definitive magneto test to determine the health of the magneto to be sure it can power the original ignition system and be done with it. Ron the Coilman


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