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Resistance?

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Phil from Maryl

09-09-2004 07:32:04

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How much resistance should I see across one of those 12 v to 6 v step down resistors that is part of a 12 v conversion? What are the symptoms of a resistor showing a short and no resistance? I know that with infinate resistance engine would not run. Just do not know what it does with a sorted resistor showing know resistance.

I have poorly running engine that I am trying to diagnose.

Anyway to test the coil with a multi meter?

Thanks

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QWE

09-09-2004 15:47:46

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Re: Resistance? in reply to Phil from Maryland, 09-09-2004 07:32:04

The coil is only half of your problem
switch to a 12 volt coil and a condensor
made for that coil.

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Novel Idea Guy

09-09-2004 14:27:32

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Re: Resistance? in reply to Phil from Maryland, 09-09-2004 07:32:04

On a meter set to the wrong range, these resistors will show up as a dead short. 4 Ohms isn"t much resistance.

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Bob M

09-09-2004 10:31:13

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Re: Resistance? in reply to Phil from Maryland, 09-09-2004 07:32:04

Phil - Ballast resistor resistance varies somewhat with temperature. I figure anything between about 2.5 and 4 ohms means the resistor is OK. A reading greater than 4 ohms - especially when cold - would make the resistor suspect.

Quick way to tell if the resistor is working? It should get too hot to touch after running several minutes. If it remains cold it's shorted. (Also a shorted resistor causes the coil to heat up and the points to burn out quickly)

Another test is with the engine stopped, the points closed and the ignition switch on you should read about 6 volts across the resistor and 6 volts across the coil primary.

It's tough assess the condition of a coil with a multimeter. Depending on the coil the primary should read between about 2 and 4 ohms, and secondary between 1,000 and 5,000 ohms. But a coil can show acceptable resistance readings and still develop a weak or no spark. Better approach is to swap it with a known good coil.

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Stan(VA).

09-09-2004 20:30:44

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Re: Resistance? in reply to Bob M, 09-09-2004 10:31:13

The voltage test Bob gave you is good. Every factory 6V coil I've checked was about 1-1/2 Ohms. So I go for a 3 Ohm 12V coil, or a 1-1/2 Ohm step down resister with the old coil, which should maintain about 4 Amps through the points (E=IR or Volts = Amps x Current).
Stan(VA).

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rustyfarmall

09-09-2004 09:16:03

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Re: Resistance? in reply to Phil from Maryland, 09-09-2004 07:32:04

I can't really answer your question but I had similar problems with my 12 volt conversion M. I solved the problem by purchasing a new 12 volt coil with internal resistor. Around $20 from my napa dealer. Problem solved.

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