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Farmall & IHC Tractors Discussion Forum
Show Parts for Model:

Coil Question

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Dunndan

04-11-2009 09:14:33
75.90.0.196



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My Super A has been converted to 12 v. I run a negative ground. No ballast resister. I went to start this morning and after a few turns of the crank not even a single hit. I double checked that the switch was on and it was. Good fuel supply. Then I checked the coil wire. When I wiggled it I felt heat. The coil (12v internal resister) was so hot it almost burned a blister on my finger. The switch had been on about a minute, no more than 2. I assume that the coil should not be heating up like this. Am I correct? I am on my way to get a new one, but would appreciate any confirmation or information. Thanks.

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Dunndan

04-11-2009 16:09:38
75.90.8.175



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 Re: Coil Question in reply to Dunndan, 04-11-2009 09:14:33  
The new coil did it. Thanks for the help.



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John T

04-11-2009 16:51:36
66.244.97.31



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 Re: Coil Question in reply to Dunndan, 04-11-2009 16:09:38  
Congratulations

John T



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John T Troubleshooting

04-11-2009 11:44:21
66.244.97.31



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 Re: Coil Question in reply to Dunndan, 04-11-2009 09:14:33  

TROUBLESHOOTING A BATTERY POWERED EXTERNAL COIL TYPE IGNITION SYSTEM:

PRELIMINARY CHECKS:

(A) To see if it happens to be a cap n rotor problem and to see if at least the coil is firing, remove the coil wire from the distributor (leave coil end intact) and place its bare end to within 1/8 inch from tractor iron, turn her on n crank her over, and see if she jumps that gap with a good visible blue spark?????? If so but the plug wire ends (from wire end to 1/8 inch to frame) or the plugs themselves don’t fire, its a cap n rotor or plug wire problem. If the coil wire isnt even sparking, see below.

(B) Next open the cap and see that the points are gapped correct and indeed opening and closing as the engine is cranked and the distributor shaft rotates and MAKE SURE THEY ARE NOT BURNED OR PITTED OR CARBONED UP BADLY !!!!!!!!!!!! If so, running a point file between them to clean them up might make her run again HOWEVER that’s only a temporary cure, so if that cleaning makes her spark, INSTALL N GAP NEW POINTS. In the event they appear good but only gray oxide coated, non abrasively clean/buff/polish them using say a dollar bill or shop cloth etc. and see what happens.

MORE TROUBLESHOOTING IF ALL THE ABOVE STILL FAILS TO MAKE HER SPARK

1) THE VERY FIRST THING YOU GOTTA HAVE is voltage to be present on the coils high supply (NOT to distributor) terminal when you turn the Ignition switch ON. If not she cant ever fire, but in the event the ignition switch or circuit/wire down to the coil or any Ballast Resistor is bad or open, you can HOT WIRE it by jumping a hot ungrounded battery voltage source to the coils high input supply (NOT to distributor) side n see if she runs then???? If she fires hot wired, you could have a bad ignition switch ((That can happen, when Ignition is on, the switches IGN terminal must turn hot)),,,,,,,or an open Ballast (if it has one) or a bad/open wire from switch to coil.

If the switch is good, if you turn the ignition switch on and place a test lamp on the coils high (NOT to distributor) terminal SHE MUST LIGHT UP. If not again, look for an open Ballast Resistor (if it has one, it should read around 1.25 to 2 ohms across its terminals) or bad/open wires from the switches IGN output down to the Ballast (if it has one) and distributor.

2a) When the Ignition switch is turned on, voltage should appear on the coils high input side. That would be 6 volts on a straight 6 volt system or 12 volts on a 12 volt non external ballasted system, or around 6 volts on a 12 volt system that used a 6 volt coil plus an external Ballast Resistor and the coil is good and the points are closed and they and ALL wiring is good.

2b) To insure the coils low voltage primary winding is not bad/open, use an ohmmeter and measure its DC resistance between its lil + and -terminals. If its an open circuit (no continuity) its bad/open and will NOT work. It should measure around 1.25 to 2 ohms or so if its a 6 volt coil and maybe 2.5 to 3.5 if its a 12 volt internally ballasted coil. NOTE CAUTION have all leads and any voltage source DISCONNECTED FROM the coil for this simple primary winding continuity test. 3) Next, place your voltmeter or test lamp over on the coils other low to distributor terminal side, turn her on and crank the engine over.

4) A test lamp there should flash ON (when points are open) and OFF (when points are closed) as the engine is cranked slowly.

5a) If the lamp never comes on there, the coils primary is bad/open,,,,,,,,,,or the points are never opening,,,,,,,,,or theres a shorted/bad condensor (remove its lead to points and see if lamp comes on, if so, bad shorted condensor or its wiring),,,,,,,,or the points wire is shorted,,,,,,,,or the distributors side pass thru stud is grounded (use ohm meter to test that),,,,,,,,,or the points may have a shorted spring.

5b) If the lamp never goes off as engines cranked, the points are not closing or are bad,,,,,,,,or the wire or circuit is missing from the distributor to the points,,,,,or the distributors not well grounded to the tractor.

She cant fire the coil unless its low side is getting a conductive ground return path via closed points and then the circuit is open when the points open.

Be sure the condensor or its wiring is NOT shorted out and see if the lite comes on (when points open) with the condensor disconnected. If removing the condensor makes her spark, replace the condensor.

SUMMARY

Be sure the points are closing fully and open on high cam and ARE NOT BURNED OR PITTED OR CARBONED UP BADLY,,,,,,,theres voltage present on distributors high side at all times when ignitions on (or its a bad switch or open ballast or bad wiring to col),,,,,,,voltage on coils low side flashes on and off as distributor is cranked,,,,,,,,,condensors not bad/shorted,,,,,,,,no shorts in wires to points and no shorts in pass thru side out distributor stud,,,,,,,,coil has continuituy.

You may luck out n just need a new set of points. If the coil wire fires (see above) and the plug wire ends to 1/8 from frame but NOT the plugs, they are badddddddddddd. Check them BOTH.

Good Luck n God Bless, post back any questions and your findings and any questions.

John T Nordhoff in Indiana, retired electrical engineer who usually lurks over on the Mother Deere boards versus over here on the “dark side”.

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JMOR

04-11-2009 11:04:43
72.181.158.237



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 Re: Coil Question in reply to mkirsch, 04-11-2009 09:14:33  

DUNNDAN said: (quoted from post at 12:56:41 04/11/09) I see what you are saying. The coil I have is a Niehoff. On the sticker it says "12V No external resister required" What do you mean when you say the distributor shorted out? The post on the side of the dist. has the wire from the + side of the coil attached on the putside. On the inside of the dist. the post has the following: a nut, then the condenser wire, then the points spring, then another nut that holds everything together. Should the condenser wire be isolated from the points spring? The points open and close fine. Gap is .021. They are new. The tractor ran fine last time I used it. Thanks for the help.


" What do you mean when you say the distributor shorted out? The post on the side of the dist. has the wire from the + side of the coil attached on the putside. On the inside of the dist. the post has the following: a nut, then the condenser wire, then the points spring, then another nut that holds everything together."

One place a short occurs is that the insulator on that post as it passes thru distr wall fails.
"Should the condenser wire be isolated from the points spring? "

No, the post, condenser wire & points spring are all common electrically.

The light bulb routine mentioned earlier is a good & easy test.
:idea:

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El Toro

04-11-2009 10:31:27
64.12.116.73



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 Re: Coil Question in reply to Dunndan, 04-11-2009 09:14:33  
Buy Napa's 12 volt coil with a builtin resistor. Cost is about $18.00. P/N IC14SB Hal



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John T

04-11-2009 09:44:44
66.244.97.31



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 Re: Coil Question in reply to Dunndan, 04-11-2009 09:14:33  
Welllllllllll its kinda hard to say just how hot that hot is over the net butttttttt that being said I wouldnt expect (given correct full true 12 volt coil or a properly ballasted 6 volt coil) a coil to get so hot it would raise a blister !!!!!!!!

Sure, if the ignition is left on a long period with the tractor not running and the points are closed a coil (even a correct one) will get pretty hot but NOT in just a minute or so

1) I would insure what youre calling call a 12 volt "internal ballasted" coil is indeed a full true 12 volt coil. If so, its internal primary resistance as measured between its lil + and - terminals will be in the 2.5 to over 3 ohms or so range BUTTTTTTT if its only like 1.25 to under 2 ohms, ITS A 6 VOLT COIL AND REQUIRES AN EXTERNAL VOLTAGE DROPPING (12 to 6) Ballast Resistor otherwise it will overheat

NOTE a full true 12 volt coil (no ballast required) may be labeled "12 volts" or "12 volts NOT for use with external ballast resistor" HOWEVER if its labeled "12 volts for use with (or requires) external ballast resistor" IT INDEED NEEDS ONE OR IT WILL OVERHEAT

If the coils output (to distributor) is constantly shorted out by a short in the distributor (where wiring terminal passes through),,,,,,,,,or the condensors a dead short,,,,,,,,or theres a wiring short,,,,,,, or the points are shorted or never opening, the coil will get pretty hot PLUS theres no spark. You may wanna insure that BEFORE you buy a new coil.

If you place a 6/12 test lamp on the coils output (to distributor) terminal with ign on and slowly crank the tractor, it MUST be flashing ON (points open) and OFF (points closed) If it never turns on theres a short like the condensor or wiring or points not opening or teh distributor input pass thru terminal is shorted to case (check that) assumign the coils primary is continuous. Check for wiring shorts and a condensor short and the distributor and insure points are openign n closing n gapped before you buy a coil.

No fire till the test lamp flashes on n off as engine rotates and points break open n closed and THERES NO SHORTS. PLUS a continuous short will heat the coil

If you want my troubleshooting procedure post back

John T

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DUNNDAN

04-11-2009 09:56:41
168.9.18.2



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 Re: Coil Question in reply to John T, 04-11-2009 09:44:44  
I see what you are saying. The coil I have is a Niehoff. On the sticker it says "12V No external resister required" What do you mean when you say the distributor shorted out? The post on the side of the dist. has the wire from the + side of the coil attached on the putside. On the inside of the dist. the post has the following: a nut, then the condenser wire, then the points spring, then another nut that holds everything together. Should the condenser wire be isolated from the points spring? The points open and close fine. Gap is .021. They are new. The tractor ran fine last time I used it. Thanks for the help.

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John T

04-11-2009 11:38:17
66.244.97.31



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 Re: Coil Question in reply to DUNNDAN, 04-11-2009 09:56:41  
The label tells me its indeed a full true 12 volt coil NO Ballast is needed.

Put an ohm meter on low Rx1 scale or continuity tester on the distributor terminal (where wire from coil attaches) and other lead on its metal casing. With points closed, it needs to read a short circuit near 0 ohms,,,,,,,,with points open it needs to read near infinity ohms open circuit.......IF IT STAYS AT 0 OHMS EVEN WITH POINTS OPEN THERES A SHORT like the points or the condensor or the lil terminal that passes thru side of distributor (where wire from coil attaches) is bad.

Check for a short then run my test lamp procedure above n see if it flashes on n off as points open n close

I will get a URL link for my Troubleshooting Procedure that will walk you through findign teh problem if you still need it

John T

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JMOR

04-11-2009 09:31:18
72.181.158.237



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 Re: Coil Question in reply to Bkpigs, 04-11-2009 09:14:33  

old said: (quoted from post at 12:18:48 04/11/09) A coil will get pretty warm but should not get hot enough to burn you. That said there are some things that can cause it to do that. Points stuck closed, a shorted condenser, or a short in the wire going to the point will in fact cause a coil to get to hot and that in turn will burn out a coil
Hobby farm



Switch left on, engine not running, & it came to a stop with points closed, is a condition presenting the same electrical circuit to the coil as a shorted condenser or points stuck closed, so if those point & condenser failures will burn up the coil, so will stalled, points closed situation.

Some of these 12v conversion/coil designs really pump a lot of heat into the coil........3 to 5 times more than factory 6v arrangement. Which is why I asked him, 'exactly what coil are you using'?

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JMOR

04-11-2009 09:25:10
72.181.158.237



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 Re: Coil Question in reply to Janicholson, 04-11-2009 09:14:33  

Dunndan said: (quoted from post at 12:14:33 04/11/09) My Super A has been converted to 12 v. I run a negative ground. No ballast resister. I went to start this morning and after a few turns of the crank not even a single hit. I double checked that the switch was on and it was. Good fuel supply. Then I checked the coil wire. When I wiggled it I felt heat. The coil (12v internal resister) was so hot it almost burned a blister on my finger. The switch had been on about a minute, no more than 2. I assume that the coil should not be heating up like this. Am I correct? I am on my way to get a new one, but would appreciate any confirmation or information. Thanks.


You say, "..coil (12v internal resister)...".

Exactly what coil do you use?

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old

04-11-2009 09:18:48
4.244.57.236



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 Re: Coil Question in reply to Dunndan, 04-11-2009 09:14:33  
A coil will get pretty warm but should not get hot enough to burn you. That said there are some things that can cause it to do that. Points stuck closed, a shorted condenser, or a short in the wire going to the point will in fact cause a coil to get to hot and that in turn will burn out a coil

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