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Grounding a low tension mag.


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Old 01-23-2005, 08:49:08 PM
hitmis1 hitmis1 is offline
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Default Grounding a low tension mag.

Do you have to ground a low tension mag. when you are running the engine on a battery? Does it hurt the mag. if you run it on the battery. I have a 6 HP Associated that I start on the battery. After it warms up I switch to the mag. I have been told it does hurt the mag. and I have told it does not hurt the mag. What do you think.
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Old 01-23-2005, 10:19:00 PM
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Default Re: Grounding a low tension mag.

I have been told that the mag will be ruined if it is left hooked up to the ignitor while a battery is also hooked up to start the the engine. I always unhook the mag when starting on a battery. I believe the mag should be grounded if not hooked up when the engine is running. The ignitors on engines with gear driven mags are designed to have the points closed except at the moment of ignition when they snap open. I can't imagine it being any good for any current generating device to run with an open circuit.

Mike
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Old 01-23-2005, 10:54:09 PM
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Default Re: Grounding a low tension mag.

Associated made an ignitor that could be used both ways. I have one that fits a 1 3/4hp and maybe others. I not sure of all the sizes it fits, but it can be switched back and forth from battery to mag and visa versa. They both remain hooked up all the time. You can also do this with a double knife switch. I have seen this done but have not done it myself. Paul Hokanson
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Old 01-23-2005, 11:17:03 PM
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Default Re: Grounding a low tension mag.

It will not harm a Low Tension mag to run open circuit. Voltage is only a few volts and will cause no harm. When the igniter trips there will be a voltage spike. If you feed current into the mag you will probably demagnetize the magnet. BUT a High Tension is another story and should either be grounded or run with a spark plug or other spark gap... True Most High tension mags have a safety gap but it is rather wide and voltage can build up and damage the coil.

True some engines have igniters that are normally closed with a low tension mag.... BUT Fuller & Johnson engines use the same igniter for battery or Low tension mag with NO Adverse effects and the larger sizes have a single pole double throw switch for starting with battery...
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Last edited by Ken Majeski; 01-23-2005 at 11:22:05 PM. Reason: Addition
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Old 01-24-2005, 11:22:10 AM
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Elden DuRand Elden DuRand is offline
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Default Re: Grounding a low tension mag.

Quote:
Originally Posted by Ken Majeski
It will not harm a Low Tension mag to run open circuit.
I concur. On low-tension it doesn't matter as long as you don't hook a battery to it. A high-tension mag is an entirely different animal and the plug wire(s) MUST be grounded or connected to a spark plug when operated.

Take care - Elden
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Old 01-24-2005, 01:17:20 PM
Tom Werner
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Default Re: Grounding a low tension mag.

Gentlemen, For the low-tension application described, I would use a single pole double throw knife switch. Wire the knife part of the switch to the ignitor and the remaining two terminals, 1.To the mag and 2. to the coil/batt source.. This would insure that the two sources never "shake hands"
Tom W in WI :
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Old 01-24-2005, 10:56:22 PM
hitmis1 hitmis1 is offline
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Default Re: Grounding a low tension mag.

Thanks for all the responses and advise. I will put a knife switch on the engine to change from battery to mag. and not both.
Thanks again and thanks to harry for SMOKSTAK.
Bill in KY
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