Magneto test thread?

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 2016: Magneto test thread?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, July 02, 2016 - 08:50 pm:

My engine dies when I switch it to magneto and my headlights go out when I switch them to low beam. These gremlins might be related but I want to start by testing the magneto output and trace the wires from there since it is easier to measure volts than dead wires.

Sorry about the babbling.

Is there a good thread or YouTube video about Magneto test specs, etc?

(Message edited by Laughac on July 02, 2016)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Saturday, July 02, 2016 - 09:08 pm:

Try the Regan - Patterson Memorial test mentioned here:

http://www.mtfca.com/discus/messages/80257/96176.html


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Saturday, July 02, 2016 - 09:32 pm:

There are several things which can cause the problems you have listed. If it ran on magneto and then suddenly stopped, you have a problem with the switch or with the magneto.

The first thing to do is to run the car on battery and check the voltage output from the magneto. This can be done by connecting a 12 volt bulb between the magneto post and ground. The light should light up. Now put an analog AC voltmeter across the light bulb. You should have at least 6 volts at idle. The voltage will increase as you speed up the engine to nearly 30 volts AC at high speed. The light bulb will probably burn out if you rev the engine.

If you find the voltage OK, you do not need to do anything to the magneto. You need to check the wiring and the switch.

If the voltage is low or non existent when you do the above test, you have a problem with the magneto. First check for endplay in the crankshaft. This test is mentioned in the link posted above. If the endplay is excessive, you will need to address that before doing anything else. Check the magneto post to see if there is lint on the contact or if the contact is connecting to the magneto plug inside. If this is OK The next thing would be to do the recharge of the magnets which is also shown on the link above. One other thing you can do is to check for continuity between the mag post and ground. You should have a very low resistance if the coils are good and connected. However, if there is a ground between the post and the last coil, it will also show low resistance. So this test will actually only show an open connection.

If the things addressed above don't fix your problem, you will need to pull the engine and replace the magneto coil ring and recharge the magnets and also fix endplay if it exists.

Only other thing I can think of which could cause your problem would be the adjustment of the coils. They should be tested on a hand crank coil tester or strobospark. I put this last because if the coils are not working right they usually will have problems when running on battery too.

As for the low beam lights, the bulbs could be burnt out or there could be a problem with the switch or wiring. Sometimes if a battery connection becomes loose or corroded and you are driving with lights on, the generator output will increase enough to burn out the lights. So check the bulbs first.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, July 02, 2016 - 10:21 pm:

Thanks Royce and Norm,

I just got the low beams to work by wiggling the switch, so that could be cause of both. The magneto will still get tested.

Several videos and Royce's 2009 thread mention recharging the magneto magnets by briefly sparking 3 x 12 volt batteries.
For safety and clarification:
1. Were the 12v batteries connected inline for 36 volts?
2. Positive to Positive of Magneto, right?
3. Engine running or off?
4. Just a few quick sparky touches of the lead, right?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, July 02, 2016 - 10:23 pm:

ChargoMagneto


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, July 02, 2016 - 10:25 pm:

I think this diagram answers all of my questions.
Thank You!

Hmmm, what did I forget to ask? Ha


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Sunday, July 03, 2016 - 09:00 am:

Here is a video of the in-car magneto recharge. Having a large crowd to watch and help seems to be part of the process. :-)

https://www.youtube.com/watch?v=Lz4MlgH8K2U


Add a Message


This is a private posting area. Only registered users and moderators may post messages here.
Username:  
Password:

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration