3020 LP coil

steve in ok · Sep 12, 2018

I have a 64 model 3020 LP that seems to be burning up points. I have 4.5 volts at the small + terminal with the key on and the points closed. When it is running it shows 12 volts at the same terminal. I am using a fluke multimeter to measure and was wondering if the meter can't react fast enough when the points close to show the 4.5 volts. Thoughts appreciated.

steve in ok · Sep 12, 2018

I will add that the coil has 1.4 ohms resistance from the + to - terminals

Bob · Sep 12, 2018

It would be interesting to check the primary voltage with an ANALOG meter and see if that would show a better "average" of the voltage, typically in the 8 to 9 Volt range.

You are measuring a "noisy" pulsed voltage, and digital meters typically "see"/average primary ignition voltages differently than analog meters.

You state that the primary resistance is 1.4 Ohms, I have two comments... 1. Did you verify that the meter reads "0" with the test leads touching? 2. Even "quality" meters can be a bit inaccurate at low resistance values.

That being said, if the measurement IS correct, that 1.4 Ohms coil primary resistance plus the 2.2 Ohm ballast resistor wire would give you 3.6 Ohms of primary resistance, which should be adequate.

To verify, check the primary current with an analog Ammeter, should be in the 3 to 4 Amps (max) range.

John T · Sep 12, 2018

If the coil ACTUALLY only has 1.4 ohms of LV primary winding resistance on a 12 volt tractor, you need at least that much or a tad more SERIES BALLAST RESISTOR OR RESISTOR WIRE OR LINK (you need a total of coil and ballast to be around 3 ohms) or else the coil runs hot and the points will burn premature. If all is well and you have a series ballast of around 1.4+ ohms ??? I would expect to see around 6 to 7 volts on the coils input with ignition on and points closed......? For these types of tests I prefer my OLD Analog Simpson 260 Meter as digitals may be all over the place. Good accurate analog voltage and total (coil + ballast) primary circuit resistance will provide good information. A bad condenser can also contribute to early points failure.

John T

steve in ok · Sep 12, 2018

Thanks for the replies. I will get an analog meter and check it with that. Thanks

3020 LP coil

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