Test Amp meter help

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2014: Test Amp meter help
Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Thursday, October 02, 2014 - 11:32 am:

Any suggestions about connecting an AC amp meter to the in car magneto? Service manual directions suggest connecting meter to output post and then to frame or engine. Similar to hooking a volt meter. Is the amp meter connected direct to ground for reading?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker on Thursday, October 02, 2014 - 11:41 am:

The AC ammeter should be connected from the magnet post to the load, such as the ignition coil.
By the way, make sure you really have an AC ammeter, they are not that common.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Thursday, October 02, 2014 - 11:53 am:

What paragraph in the service manual are you reading?
Paragraph 994 talks about connecting a voltmeter between the mag terminal and "a clean part of the cylinder or transmission cover"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Zahorik on Thursday, October 02, 2014 - 11:59 am:

Why are you interested in measuring the magneto current? If you are interested in testing the output of the magneto there is an excellent method described on the forum using a 1156 lamp bulb. Connect the lamp bulb from the mag terminal to ground and with the engine running, vary the engine, the lamp should vary from dim to very bright or even blown out. You could use a voltmeter on the terminal and you should get a few volts at idle to maybe 35 volts at a high RPM.

DO NOT connect the ammeter as a volt meter. Voltage is an across measure, whereas current is a through measure. A voltmeter is connected to ground and the point of interest, such as the magneto terminal, nothing is disconnected.

To measure magneto current, you must disconnect the magneto terminal wire. Connect on lead of the ammeter to the mag post and the other to the magneto wire that was just disconnected.

Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Miller, Mostly in Dearborn on Thursday, October 02, 2014 - 12:01 pm:

An ammeter hooked from the mag post to the frame will burn up. You are describing the connection for a voltmeter.

An ammeter must be placed in series with a load that is within the capacity range of the ammeter.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Hood on Thursday, October 02, 2014 - 12:29 pm:

George, check Frank's T Parts.

www.frankstpartsltd.com


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Hood on Thursday, October 02, 2014 - 12:34 pm:

Well, that link says that Lang's has taken over all sales, but try this link which shows pictures of installation.

www.frankstpartsltd.com/default_files/Page923.htm


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Thursday, October 02, 2014 - 03:33 pm:

Ford Service Bulletin 15 Oct 1926. Two leads are attached to the tester; when checking the magneto one of these leads is clipped to either the engine or the frame of the car the other is clipped to the magneto terminal post ("A"). ... Testing a magneto. To test the magneto first test its strength at starting speed. To do this, turn the engine over with the starter leaving the ignition off. ..... proper reading is 3.5 amps.

Unless the magneto tester has a built in load, which is not indicated, the directions sound similar to connecting a volt meter.

Prior to 1926 for 15 September 1919, the Bulletin has values for magneto out put 2000 rpm 6.1 amps, 600 rpm 8.5 amps, and to 1200 rpm 9 amps.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Thursday, October 02, 2014 - 04:23 pm:

The Bulletin is describing a specific tool, the KR Wilson Magneto Tester, for AC amps.

If just wanting to know the output of the Ford magneto in a linear way, using Frank Fenton Magneto Meter is just as easy. It reads in AC volts. Have one on my T and it works swell.



Fast idle



Slow idle


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Thursday, October 02, 2014 - 07:41 pm:

The Bulletin is describing a specific tool, the KR Wilson Magneto Tester, for AC amps.

What is in the Wilson Tester for a load? Resistance value?
Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Friday, October 03, 2014 - 08:54 am:

Not having the KR Wilson Magneto Tester, but an ampere meter with a range from 0 to 15 amps AC, would this work? To rest the amperage output of a magneto by using the starter, the resistance would be about 3.33 to 4 ohms? If volt output is 30 VAC, and max amp output 9 amps AC.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Zahorik on Friday, October 03, 2014 - 10:44 am:

I don't believe the the KR tester uses a resistive load. It has a combination of resistance and inductance so as to better approximate the actual load the car (mostly ignition) places on the magneto.
Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Friday, October 03, 2014 - 05:22 pm:

Thanks. Then it may be possible to replicate the load with a meter in series with a (buzz) coil. Wire from magneto to amp meter, amp meter to coil, and coil to ground?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Friday, October 03, 2014 - 08:38 pm:

In my view if you want a serious tester to evaluate the Model T magneto get a St Louis Magneto Tester made by FunProjects. This is by far the most stringent and simple test.
The next best alternative is the 1156 bulb and AC voltmeter test, but the results can fool you adn should be subject to a review by a knowledgeable evaluator.
I have never taken a close look at the KRW tool so I cannot comment.
The Hoyt and "Magneto Meter" shown above are not all encompassing and definitive tests of the health of the Model T magneto.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Saturday, October 04, 2014 - 09:40 am:

I have a period amp meter and need a winter project. I believe the following patent (circa 1916) shows the circuit design and the use of an ignition coil as the inductor/resistance may just work.

http://www.google.com/patents/US1270100

Thanks for the assistance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Saturday, October 04, 2014 - 12:10 pm:

Looking at fig. 274 shows that full scale is 10 AC amps.

Upon reading the service bulletin, one part says:

" Cars equipped with magneto ignition only must be tested in a different manner, as the test meter when attached to the contact post cuts out the magneto ignition."

This leads me to believe that the KRW device is just basically a 10 amp AC ammeter.

If you use any type of resistance or inductance for testing, the magneto output will be restricted by the impedance of the resistance/inductance.

George, what is full scale of your period amp meter?


Top of pagePrevious messageNext messageBottom of page Link to this message  By George John Drobnock on Saturday, October 04, 2014 - 01:03 pm:

The meter is listed as a Jewell Portable A.C. Ammeter (pattern 11). Manufacture date 1927. Rated at 15 amps AC.

I read the same description that the meter connected to the magneto would short out the magneto and power to the coils. However the suggestion that if a starter was available on the car it would be possible to secure a current output by using the starter to turn the engine. An other way to check output.


Posting is currently disabled in this topic. Contact your discussion moderator for more information.
Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration