re-172 Ford electrical

flying belgian · Aug 28, 2017

Ok, how does this route? Power from bat. to resister, from resister to + on coil, from - on coil to points where condenser is also connected. High tension wire on top of coil to
center of dist. cap. to rotor. Then high tension is directed to each plug wire. So the center of rotor must be ground right? I have 12 volts at + and - on coil. I have 12 volts at
point contacts but I have nothing coming off high tension of coil. I assumed the coil was bad so I replaced it. Still nothing. I replaced the coil wire. Still nothing When and
how does the condenser work? Could that be the reason for no spark off coil?

JMOR · Aug 28, 2017

(quoted from post at 15:12:49 08/28/17) Ok, how does this route? Power from bat. to resister, from resister to + on coil, from - on coil to points where condenser is also connected. High tension wire on top of coil to
center of dist. cap. to rotor. Then high tension is directed to each plug wire. So the center of rotor must be ground right? I have 12 volts at + and - on coil. I have 12 volts at
point contacts but I have nothing coming off high tension of coil. I assumed the coil was bad so I replaced it. Still nothing. I replaced the coil wire. Still nothing When and
how does the condenser work? Could that be the reason for no spark off coil?

hen points are closed, that grounds the (-) side of coil & neither that nor either side of point contacts should show any voltage.

Janicholson · Aug 28, 2017

With the Key (Ignition) on, the Circuit should be from the I terminal of the key or ignition switch to the resistor. (resistors are sometimes integrated into the wire from the switch) there should be battery voltage there or ~6 volts if wire resistor. If 12v there, it should not have an additional resistor. From the resistor to the coil positive (if negative ground) there should be ~6v there if the points are closed. From the negative side of the coil there should be no volts if the points are closed. With the points open, there will be 12 volts even with a resistor). Most engines stop with the points closed, so there should be no voltage at the points connection (assumes closed points. If there is voltage there, and the points are closed, they are not making contact, clean them.
There is never voltage at the center terminal it is connected, but has high resistance and will not show volts. Measuring from the coil negative to the center terminal with an ohm meter set on 10k ohm scale should make a resistance reading. Jim

flying belgian · Aug 28, 2017

If I'm getting no spark from the coil wire can my problem be the condenser?

Janicholson · Aug 28, 2017

With the points closed, key on, measure voltage from the stationary point to the movable point arm, if voltage the points are dirty. Condensers do not cause this action as described. Jim

teddy52food · Aug 28, 2017

yes. Try a known good one.

kevinthefixer · Aug 28, 2017

Jim and Teddy are both right, but Jim's test is quick and easy, Teddy's involves changing a part that you might not have handy. And even with a bad condenser you should still get a weak spark at the coil output, and a very visible one at the points themselves. You need to get power on, then off, at the negative side of the coil for spark to happen. A test light between coil negative and ground should blink rapidly as the motor turns over. If it's on all the time the points are not grounding the coil ngative; if it's never on either there's no power getting to the coil, no power getting through the coil, or the points are never opening the circuit (either because they are not opening, or the wiring to them or even the condenser is shorted to ground).

re-172 Ford electrical

flying belgian

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JMOR

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Janicholson

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flying belgian

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Janicholson

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teddy52food

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kevinthefixer

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