Coil question

[jon f mn]

Tried to start my dc case the other day and ot didn't want to start. Ive been having intermittent problems with that for a while. As usual there have been several small issues such as a bad bat cable and loose wires. This time when I cranked it it fired and died then wouldn't fire. When I put a test light to it I found that the power coming out of the coil was lower than going in. I don't have a meter, but the light was brighton theinput and dim on the distributer side. There is a resister between the coil and distributer, but the light was dim before the resister. Do I have a bad coil or should it be that way? I'm not sure because it's been a while since I checked it, but I don't remember the light being dim on either side before.

 

[Jiles]

The simplest way I know to "shade tree" check a coil--not saying you are a shade tree, is to check spark from high tension lead while touching a ground wire to the "-" post on coil. and a hot wire connected to "+". The small wire gconnecting the distributor to "-" , should be disconnected.
Every time you touch the ground wire to coil, there should be a spark.
You are basically eliminating the points.
Of course this doesn't mean it is hot enough.

 

[Janicholson]

For a resistor between the coil and the points, with the ignition on and points closed, not running, there will be a dim light on the dist. side of the coil. That is not my normal position for a resistor in the circuit. it should be placed on the Key or switch side of the coil input. The resistor between the coil and points might (arguably) cause a degradation of the points/coil/condenser discharge interaction. See if the points open and close with the correct gap. When open, the voltage will read battery volts all the way to the points through the resistor. Jim

 

[DeltaRed]

I had a coil completely fail on my Super H a while back. After all the 'usual tests' ,I finally swiped a coil off another old tractor. The tractor then fired right up.Do you have a 'spare' coil to try?

 

[old]

I have found test light to be a poor way to test ignition problems. From what your saying I would almost bet your points need to be cleaned and once there good and clean and when opened by hand with ignition of and have a spark it will probably start

 

[gene bender]

you dont put the res between the coil and dist you put it on the batt side if you have 12v if still using 6v no res.

 

[jon f mn]

Hmmmm. It's been that way for at least 20 years. Not saying your wrong since I knew little about it when I did it. Wonder why it lasted so long? Always started right up til I started having issues with corrosion and loose wires over the last year or so. I think the points, condenser, cap, rotor, and wires are all still from then too. Guess it's time for a tune up.

 

[old]

Having the ballast resister on either side of the coil work just fine. Ya the common way is to have it before the coil but either way it does work. The coil may see 12 volts which could be hard on it but not really sure if that would be correct or not belong to long since I have studied electrical theory. Been out of electronics's school for 42 years now

 

[JMOR]

Yep, conventionally ahead, but makes absolutely no difference which side of coil it is on, as all it is really doing is setting coil primary current level. Equivalent circuits both reduce to same.

 

[Case Collector]

If the ballast resister is the right size the neg. terminal of the coil will have 6 volts on it when the points are closed and 12 volts when the points are open , this only true when you have the resister between the coil and the dist. as you do