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Ford 9N ignition question.

Years ago my neighbor and I bought a 9N tractor together. we used the tractor for many years and then for various reasons we parked it for several years. Deciding to use it again I wasn't able to get any spark, even though it worked fine when we parked it. After cleaning the points I was able to confirm that the points were properly adjusted and making contact. Opening and closing the points by hand resulted in an erratic and weak spark. Tracing the really simple electrics I found that the power from the battery goes through a ballast resistor. Unlike cars and other vehicles with ballast resistors that I'm familiar with the ballast resistor is bypassed during starting. But the old Ford 9N tractor doesn't do this. I ended up connecting the coil directly to the battery and this resulted in a pretty good spark. Good enough that the tractor started right up. So why the ballast resistor? Why would the current need to be limited for regular operation if the ballast resistor isn't bypassed during starting? Anyway, I am not going to run the tractor with the ballast resistor out of the circuit because It is supposed to be there. And before it was parked for several years it worked just fine. I think the reason for the poor spark must be corroded connections somewhere in the ignition circuit. But I'm still wondering why they designed the ignition circuit with a ballast resistor. Anybody know? Thanks, Eric

Reply to
etpm
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On 04/24/2017 3:35 PM, snipped-for-privacy@whidbey.com wrote: ...

Reply to
dpb

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The resistor AND a coil designed to generate the spark with a lower input voltage decreases the time for the magnetic field to build up when the points close, without overheating the coil from its internal resistive loss.

Reply to
Jim Wilkins

On Monday, April 24, 2017 at 4:34:08 PM UTC-4, snipped-for-privacy@whidbey.com But I'm s till wondering why they designed the

The total resistance is the wiring, the ballast resister , and the resistan ce of the coil primary. If all the resistance was zero, the current would initially be controlled by the inductance of the coil, but would be high an d burn the points. Some coil essentially have a built in ballast resistor and do not need or use an external ballast resistor.

When you are starting the engine the voltage is lower. So if you short out the ballast resistor it is closer to how it is when the engine is running. So even with the lower voltage when starting , you get a good spark.

Dan

Reply to
dcaster

On Monday, April 24, 2017 at 4:34:08 PM UTC-4, snipped-for-privacy@whidbey.com wrote: I think

Forgot to say that the weak spark might be caused by a bad condenser. THe condenser helps keep the spark from occurring across the points instead of at the spark plug.

Dan

Reply to
dcaster

Is it still running the original 6 volt electrical system, or has it been converted to 12 volts? If switched to 12 it is a voltage dropping resistor.

Reply to
clare

Round or square coil? Square coil used a resistor, round coils did not. Measure primary resistance of the coil.

Reply to
clare

Thanks for the link. It explains it perfectly. Eric

Reply to
etpm

I know about the shorting Dan, read my post that you replied to a little more carefully. I wanted to know why the ballast is there when it is never bypassed. dbp sent me a link and now I understand. Eric

Reply to
etpm

Everything is original. But now I know why the ballast resistor is there and I am convinced that the poor spark is just from bad connections. I suspected the condenser but the points aren't making big sparks like they do when the condenser is bad. Eric

Reply to
etpm

I've got no familiarity with what a condenser is (outside of HVAC) in car circuitry. But thanks for saying what it does.

Reply to
bruce2bowser

It also slows the burn-up rate of the contact points. I remember very well when a tuneup lasted only 6,000 miles. I made a living from it. ;)

Hey IGGY, got any of those tractor manuals on your site?

Reply to
Larry Jaques

It is actually a Capacitor. A rose by any other name - - -

Reply to
clare

Right. "Condenser" is the old name for it. It disappeared in radio decades before automotive types abandoned the term.

Reply to
edhuntress2

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The green lines are energy stored as magnetic field in the coil, the black ones are energy stored as electric charge in the capacitor. The oscillating transfer of energy between them is similar to a swinging pendulum that swaps its energy between speed in the middle and height at the ends.

Reply to
Jim Wilkins

If the "condenser" were open, you'd get big sparks. But if the condenser is bad shorted, or nearly so, you'd get a weak spark at the plug and no spark at the points.

Reply to
Bob Engelhardt

Last night I cleaned some of the connections in the ignition circuit. I started the tractor using the "hot wired" connection first just to make sure the tractor would start. I let it run for less than 10 seconds and shut it off. After removing the hot wire that went directly from the battery to the coil I tried starting the tractor the normal way and it lit right up. It looks like plain old corrosiion problems because the tractor sat for so long without being started. The original wiring harness has been repaired a wire at a time by previous owners and is kind of a kluge. Even though it all works the ammeter has always been bypassed. I don't even know if it works. So I'm gonna order today a new wiring harness and ammeter because the ammeter looks like it has corroded inside. It's amazing how much stuff is still available brand new for the old Ford 9N, 2N, and 8N tractors. The only part I haven't been able to find new is the tube which carries the spark plug wires. I wonder why since everything else seems to be available. Even new engines. About 18 years ago the hydraulic piston assembly under the seat on this tractor needed to be replaced. I ordered one from a catalog and was surprised at first that it was made in Taiwan. Thinking about it made me realize that it made perfec sense as these tractors and the nearly identical Ferguson tractors were sold world wide. Eric

Reply to
etpm

Its just that a condenser also refers to the hot, liquid, high pressure 'low side" of a vehicle's air conditioning system. Its not always a good idea to have two different auto parts with the same name.

Reply to
bruce2bowser

They've got to do something about "wheel," then.

I haven't heard "condenser" for "capacitor" for a long time. I'll have to look at my really old engine books to see when it last showed up.

Reply to
edhuntress2

Then there's two different fenders, and two different hoods, dpending where you are in the world.

Reply to
clare

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