Bad Ford resistor

[butch27]

I saw in the drawing that  the resistor wire runs from START- I have mine on IGN because the neutral safety switch goes to start.?? Am I wrong?

[wayne petty]

butch....    if it runs ok without it...  great... it is only used while the engine is being cranked...

put a test light on the positive side of the coil... see if it gets power while the key is turned to the crank position...

if it has power to the coil while the key is turned to the crank position.. you don't need the bypass circuit...

on the fairmont...  they ran the I terminal to the white wire on the ignition module white wire..  this retards the ignition 10 degrees just for starting...


so if you have power while cranking on the coil positive wire, you don't need the I circuit...

[38HAULR]

In a ballast system without the bypass connected you will have volts alright- low volts to the coil during cranking.
You can get away with it,but at times with a low battery or even if the coil is hot you will have hard starting.  A coil used in a ballast system is actually a coil designed for 7 or 8 volt operation hence the ballast in run mode,this can be a resistive wire or an external resistor. On cranking the resistor is bypassed and the coil is still getting it,s voltage to operate at it,s best due to the battery voltage drop during cranking.
Let me share a story. In 2005 I purchased a 66 Mustang that had been in this country for a year,the guy I got it from told me "It is a mongrel to start when hot". And he only took it out on sunny weekends.
Using this vehicle as an everyday driver soon showed what he meant,nothing is more embarrassing than cranking the daylights out of a car that will not fire in a car park.
I figured enough is enough and on a Sat afternoon did some tests got the vehicle hot and then did some tests ,it became obvious that the volts were low on cranking at the coil +ve. The coil mounted on the front of the block had me thinking crook coil or one that was grossly inefficient when hot. I replaced it with marginal improvement,doing more wiring checks  I discovered that the bypass wire to  the solenoid was,not connected at all,and the solenoid was a newy,tidying up this bit of wiring has her firing up first flick,hot or cold. I figured that the prev owner looking for a fault had replaced the solenoid,the dirty terminal on the wire,and folded back suggested to me that it was off for a long time Surprisingly with the original condition, cold starting was ok ,it was coping,once the coil heated and lost some efficiency it was enough to make life difficult.......Frank.

[GPster]

I'm following all these questions and answers and I wonder if everyone is putting this combination together differently. A '79 Ford engine with a '68 points distributo in a model "T". There was talk about a module which the '68 distributor would not have and the engine starting and running with-out a wire comimg from the "I" on the starter solenoid/relay. Another possibility might be that when the engine is cool it will start on reudced voltage to the coil so it doesn't need the circuit from "I" that by-passes the ballist. Maybe the ignition switch is not related to this '79, '68 combination. If it starts and runs with-out the "I" wire then the switch is feeding the ignition circuit then the Ignition terminal on the switch is hot when the engine is cranking. If the switch is after-market or the switch out of the '79 with an ignition module then it doesn't suit the rest of the system. You say that you were burning up ballist resister. Does that happen when the "I" wire is on and you're trying to start the engine? I know what the ballist is supposed to do but I don't know what causes them to fail. If you're feeding it with 12V while cranking and the "I" circuit is keeping 12V on the other side of the ballist then the ballast wire is has 12V on both sides of it. That may not burn it up but if the ignition circuit is in contact while cranking maybe you've got power backfeeding so that the "I" wire is trying to power the accessaries through the ballist backwards. Now add that to the recipe and stir well. GPster

[GPster]

I'm following all these questions and answers and I wonder if everyone is putting this combination together differently. A '79 Ford engine with a '68 points distributo in a model "T". There was talk about a module which the '68 distributor would not have and the engine starting and running with-out a wire comimg from the "I" on the starter solenoid/relay. Another possibility might be that when the engine is cool it will start on reudced voltage to the coil so it doesn't need the circuit from "I" that by-passes the ballist. Maybe the ignition switch is not related to this '79, '68 combination. If it starts and runs with-out the "I" wire then the switch is feeding the ignition circuit then the Ignition terminal on the switch is hot when the engine is cranking. If the switch is after-market or the switch out of the '79 with an ignition module then it doesn't suit the rest of the system. You say that you were burning up ballist resister. Does that happen when the "I" wire is on and you're trying to start the engine? I know what the ballist is supposed to do but I don't know what causes them to fail. If you're feeding it with 12V while cranking and the "I" circuit is keeping 12V on the other side of the ballist then the ballast wire is has 12V on both sides of it. That may not burn it up but if the ignition circuit is in contact while cranking maybe you've got power backfeeding so that the "I" wire is trying to power the accessaries through the ballist backwards. Now add that to the recipe and stir well. GPster

Put an r on the end of the word distributo and substitute the word resistor every place I mis-used the word ballist. And I think I'm someone that can help> GPster

[38HAULR]

In run mode GPster  the "I" terminal should not be the source of any voltage. It should be floating.  Best way to check is to remove the wire at the solenoid "I" terminal and check for voltage with engine running. If the wire is connected and engine running you should see the coil +ve voltage that is now sourced via the ballast resistor.
The ballast will only fry itself due to excessive current,and the only path  is via the coil and points ,  it is normal for it to get warm/finger hot, but not burn up of course.........Frank.

[enjenjo]

In run mode GPster  the "I" terminal should not be the source of any voltage. It should be floating.  Best way to check is to remove the wire at the solenoid "I" terminal and check for voltage with engine running. If the wire is connected and engine running you should see the coil +ve voltage that is now sourced via the ballast resistor.
The ballast will only fry itself due to excessive current,and the only path  is via the coil and points ,  it is normal for it to get warm/finger hot, but not burn up of course.........Frank.

Frank is right. the only thing that will burn up the resistor is too much current flowing through it. The points alone won't do that.

[38HAULR]

Which leaves a defective coil, or  capacitor in the distributor.........Frank.

[38HAULR]

One more thought,if it ran better with the "I' terminal disconnected, then this may have a leakage to earth and loading the system,a likely source of excessive current draw,in a prev post I mentioned that this terminal is floating in run mode......Frank.

[butch27]

GP--I think you may be on to something. The Ign. switch is just a 4 prong Whitney item. I'll have to let this sink in.LOL

[wayne petty]

IGN 1 From the Switch to the resistor  switches on full battery voltage to the resistor...

the Resistor to the Coil...   the resistor reduced the voltage available for the coil positive

the relay I terminal to the ballast resistor... this is the by pass circuit..
if you notice this circuit hooks to the far end of the resistor...
when the starter solenoid is activated... the I terminal gets power directly from the battery,  when ever the ignition is on.. there is power on this wire.. but usually less than 10 volts... the I terminal only comes up to full battery voltage when the relay is activated..

the ignition switch S terminal to the relay S terminal.. this wire supplies power to activate the solenoid to crank the engine..

[GPster]

GP--I think you may be on to something. The Ign. switch is just a 4 prong Whitney item. I'll have to let this sink in.LOL

I Guess I read you wrong too. I thought you were saying that it started and ran without the "I" wire hooked up. Which would mean that you were getting ignition power through the ignition switch when the starter was cranking. Of course if there is no "I" on the ignition switch you would be getting power to the resister/coil when the switch is on start. The other idea was if the resister is burning up during the start mode when "I" is hot on the solenoid you would be getting power to the coil and the low voltage side of the resister from "I". There is no diode on that resister so that 12V would go backwards through the resister. If the switch did not have an ignition circuit was not separate during start than everything hooked to the power side of that switch might act some like it is getting power from the "I" terminal of the solenoid through the resister and back the ignition wire to the ignition switch. Just trying to throw ideas your way. GPster

[38HAULR]

The ign feed to the coil via ballast  is still present on cranking . ....Frank.

[enjenjo]

The ign feed to the coil via ballast  is still present on cranking . ....Frank.

Not always. Many GM cars are wired with ignition power on a seperate circuit when cranking.

[butch27]

It DOES run without the "I" wire. which is disconnected now.?