12 volt conversion

[20 20]

Okay so I did the 12 volt conversion on my 800 series tractor. The issue I'm having is there doesn't seem to be enough juice making it to the coil to start it. I can run a hot wire from the switch to coil{bypass resistor} to get it running then unhook the hot wire and it runs fine. If I try to start it by just using the resistor it won't fire. I did by another coil {internal resistor} but it still has the same issue. While the starter is cranking it doesn't seem to have enough juice to power the coil, an ideas? Thanks

 

[Travelover]

I believe that vehicles with coils are wired so the resistor is bypassed while cranking, then the coil is powered through the resistor once the engine is running.

When the resistor died, Old Mopars would famously start right up, then quit as soon as you released the key to the run position.

 

[Soundguy]

need to know what resistor you have and what coil you have.

I seriously dooubt you got a coil that claims it has an internal resistive element. coils today are simply produced with the correct diameter and length of the primary winding to produce the impedance requird ont he coil primary.

A coil like a napa IC14SB is 16$ and needs no external resistor.

how old is the ignition switch and how do the electrical connections look?

for a 12v system you want 3-3.5 ohms of primary resistance..

I personally would get rid of the power wasting resistor and get a real, native 12v coil like the IC14sb

soundguy

soundguy

 

[Soundguy]

I believe that vehicles with coils are wired so the resistor is bypassed while cranking, then the coil is powered through the resistor once the engine is running.

When the resistor died, Old Mopars would famously start right up, then quit as soon as you released the key to the run position.

the NAA certaintly did NOT leave the factory with a bypass relay setup on the igntion.

it was 6v when oem, and used a 6v coil and no resistor.

soundguy

 

[Travelover]

the NAA certaintly did NOT leave the factory with a bypass relay setup on the igntion.

it was 6v when oem, and used a 6v coil and no resistor.

soundguy

The systems I am familiar with on older cars don't use a relay, they are simply wired so the coil gets 12 volts directly during cranking (as does the starter solenoid) and 12 volts to the coil resistor in the run position. It seems like the OP is saying that this scheme works when he hot wires it to achieve the same result.

 

[Soundguy]

you might want to brush up on your electrical terminology.

the relay I spke of is the starter solenoid.

4 terminal 'bypass' styel solenoids are common... when the starter solenoid ( RELAY ) is energized, it not only energizes the starter but sends bat power to the coil, "BYPASSING" any ignition resistors in line.

as I stated before , the NAA DID NOT use any sort of bypass style solenoid (RELAY ) in it's original scheme.. and it was 6v using a 6v coil.. thius no ignition resistor needed anyway.

soundguy

 

[BobRip]

The systems I am familiar with on older cars don't use a relay, they are simply wired so the coil gets 12 volts directly during cranking (as does the starter solenoid) and 12 volts to the coil resistor in the run position. It seems like the OP is saying that this scheme works when he hot wires it to achieve the same result.

I think with that design the relay would be paralleled with the starter and the starter would ground out the resistor when not cranking. This assumes the resistor it tied to the positive side of the coil.

 

[Soundguy]

this isn't hard guys.

it's a 4 post relay

1 post from the bat, 1 post to the starter, one post from the spring loaded start position on the key ( switched 12v ) and one post to the coil side of the resistor.

when the post from the key is powered, the other small post is fed 12v as well, which ithen feeds 12v to the coil, thus BYPASSING the resistor. at the same time the 2 large contacts are closed so bat is fed to starter.

no rocket science.. just electromechanical switches. think of a DPST set of contacts with a single common feed ( yet seperate isolated outputs ) one oputput to starter.. one to coil.. seperate switches, so after starting the starter is not loading the ignition ckt.

soundguy

 

[Jbrink64]

the NAA certaintly did NOT leave the factory with a bypass relay setup on the igntion.

it was 6v when oem, and used a 6v coil and no resistor.

soundguy

Seems to be 12v w/ a resistor now

 

[Army grunt]

Put a wire (#12) on the starter pole an bypass the resistor. when you hit the starter it will give 12 volt right to the points.When you let off starter it will see the resistor voltage, an save your points.
Army Grunt

 

[20 20]

need to know what resistor you have and what coil you have.

I seriously dooubt you got a coil that claims it has an internal resistive element. coils today are simply produced with the correct diameter and length of the primary winding to produce the impedance requird ont he coil primary.

A coil like a napa IC14SB is 16$ and needs no external resistor.

how old is the ignition switch and how do the electrical connections look?

for a 12v system you want 3-3.5 ohms of primary resistance..

I personally would get rid of the power wasting resistor and get a real, native 12v coil like the IC14sb

soundguy

soundguy

:thumbsup: that's exactly what napa had sitting on the shelf {now on my tractor}. They said at one time they were very common but now they only need one once in awhile, but they still keep them.

 

[20 20]

Put a wire (#12) on the starter pole an bypass the resistor. when you hit the starter it will give 12 volt right to the points.When you let off starter it will see the resistor voltage, an save your points.
Army Grunt

I now have the coil that doesn't need the resistor, so I've bypassed{removed} the resistor all together. It I get it spinning fast enough{catch it just right} once I let off the starter button it will fire. As long as the start button is engaged it won't fire.

 

[Soundguy]

Seems to be 12v w/ a resistor now

and??? it was dark when I woke up.. but ain't now...???


soundguy

 

[Soundguy]

Put a wire (#12) on the starter pole an bypass the resistor. when you hit the starter it will give 12 volt right to the points.When you let off starter it will see the resistor voltage, an save your points.
Army Grunt

would be cool if that worked.. but WON'T.

the feed from the starter pole to the coil will flow current in both directions.. thus power will flow from the coil to the starter.. which has very low ressitance and will look like a short.

to do a bypass ignition setup you need a bypass style solenoid ( RELAY ).

soundguy

 

[Soundguy]

:thumbsup: that's exactly what napa had sitting on the shelf {now on my tractor}. They said at one time they were very common but now they only need one once in awhile, but they still keep them.

the ic14sb does not need a resistor to run on 12v.


soundguy

 

[Soundguy]

I now have the coil that doesn't need the resistor, so I've bypassed{removed} the resistor all together. It I get it spinning fast enough{catch it just right} once I let off the starter button it will fire. As long as the start button is engaged it won't fire.

that is some serious voltage drop you got there... try this.

run a hot wire directly from the battery to the coil primary and see if it makes a difference. if it does, then you have bad connections in the ignition circuit.

if it don't. I'd say your bat cables are undersized or coroded, or have a bad connections.. bat is weak.. or starter is drawing way more than it should. shouldn't see less than about 10v on the bat when starter is spinning over.

post back.

you are using the oem interlocked thumb switch on the tranny cover and oem solenoid correct? or has it been butchered with a key start ignition.

if key start.. make sure you have the key wired correctly so the coil is getting power during the start spring loaded position.

PS.. i'd loose the key-to-start system.. it's dangerous and bypasses the built in safety interlocked starter setup

soundguy

 

[20 20]

the ic14sb does not need a resistor to run on 12v.


soundguy

Resistor is gone wire goes straight from key switch too coil.

 

[Soundguy]

starting ok now.. or still has problems starting.

the ignition and starting ckts on these machines are painfully easy to maintain and repair.. so keep me informed on your progress so we cn get you going reliably.

soundguy

 

[BobRip]

Put a wire (#12) on the starter pole an bypass the resistor. when you hit the starter it will give 12 volt right to the points.When you let off starter it will see the resistor voltage, an save your points.
Army Grunt

When you let off the starter the resistance of the starter is so low the resistor /coil lead will be at zero volts. The machine will start and not run. Add the relay.

 

[Soundguy]

yeah.. I think AG missed a day in basic electronics concepts class..

soundguy