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Farmall & IHC Tractors Discussion Forum
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Checking coils and wiring

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relane

12-07-2006 06:39:08




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Hi, How do you check a coil to see if juice is getting to it and then going through it. Does the wire from the battery have to go to a regulator and then the coil or can it be bypassed and go directly battery(-) to coil, per example that i found, my tractor does not have lights, so im not worried about the wiring to the light switch in this example. Thank you for your thoughts.

[IMG]http://i11.tinypic.com/4hwgl8p.jpg[/IMG]

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John T

12-07-2006 08:25:21




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 Re: Checking coils and wiring in reply to relane, 12-07-2006 06:39:08  
Relane,

QUESTION:

"Hi, How do you check a coil to see if juice is getting to it..... ..... .."

ANSWER:

What I do is turn the ignition switch ON (DUH) and then place a test lamp on the coils high input (NOT to distributor) terminal and it ought to glow. Its better to use a voltmeter and then you can really tell more. Unless its a ballast resistor system (12 volt tractor and 6 volt coil) the voltage ought to be near the same voltage as the battery. With the ignition points closed (best way to do these tests) if all is good n wired correct if the voltage on the coils input (NOT to distributor) terminal is like a volt LESS then battery voltage, then I suspect a faulty resistive ignition switch and the spark is gonna be weaker. If the tarctor doesnt spark cuz theres low or no voltage getting to the coils input with th ignition switch ON its easy to simply "Hot Wire" the coils input n see if she sparks then ???

QUESTION

" ..... .and then going through it."

ANSWER

Place a test lamp over on the coils other low (to distributor) terminal. If juice is getting through the coil (its primary windign is good n continuous) then the lamp should glow ON when the points are open but be OFF when they are closed (where they normally are when setting) What I do is have the test lamp on the coils low (to distributor) terminal n turn her on n crank the engine over (have coil wire removed so she dotn start) and the lamp ought to flash On n OFF as she cranks. If the lamp never turns on, the coils primary is bad/open or the points arent opening or are shorted out but if it never turns off, the points arent good or arent closing or theres a wirign problem

QUESTION

Does the wire from the battery have to go to a regulator and then the coil or can it be bypassed and go directly battery(-) to coil

ANSWER

The ignition feed is usually fed off the ammeters load terminal or the LOAD terminal on a 4 pole Voltage Regulator,,,,, ,,,to the BAT input terminal on an Ignition Switch,,,,, ,,out the ignition switches IGN output terminal,,,,, ,,down to the coil. If the switch or circuit is bad you can "Hot Wire" the coils input from any hot batery voltage source such as the hot ungrounded battery post or the BAT terminal on a VR or Cutout Relay etc.

As far as your light problem, the light switch needs hot batetry voltage on its BAT input terminal which is typically obtained off the ammeters load terminal or the LOAD terminal on a 4 pole VR. Then when on its output terminal feeds the lights. Sooooo oo you may not have voltage getting to the switch and you need to check where its coming from (ammeter load terminal or LOAD terminal if you have a 4 pole VR) and make sure its gettign voltage and then if so, the switch and its wiring to lights n lights also gotta be good.

NOWWWWW W theres also simple tests to see if the coil is firing independant from any distrbutor i.e. see if the coil is good so post back if you need that HOWEVER shes never gonna spark until you get voltage on its input terminal so verify that first then we will troubleshoot the coil further if we need to

Let us know

best wishes n God Bless

John T

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Bob M

12-07-2006 07:11:39




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 Re: Checking coils and wiring in reply to relane, 12-07-2006 06:39:08  
Relane - To check if the coil is getting power, remove the distributor cap and temporarily block open the breaker points (manually open the contacts then place a match flap, $1 bill or similar between ‘em).

Now turn on the ignition switch and test with either a voltmeter or low current test light. If everything is OK you will see battery voltage between BOTH coil primary terminals and a good ground.

If no voltage at either coil terminal the coil is not receiving voltage – look for a bad ignition switch or wiring to/from the switch.

If voltage is seen only at the coil's ignition switch (-) terminal but not at the distributor (+) terminal, the coil is bad (open circuit in the primary).

---

Power for the ignition switch should be taken from the ammeter post NOT connected to the battery. It'll work connected directly to the ungrounded (-) battery terminal, but it will cause the ammeter to read incorrectly.

Hope this helps!

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Allan In NE

12-07-2006 07:17:49




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 Re: Checking coils and wiring in reply to Bob M, 12-07-2006 07:11:39  
Hey Bob,

Maybe you could build a shot of the coil's induction/collapse effect?

I don't think a lot of guys understand how the juice transfers from primary to secondary voltage.

Just an idea,

Allan



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Bob

12-07-2006 08:19:41




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 Re: Checking coils and wiring in reply to Allan In NE, 12-07-2006 07:17:49  
AMPACITY, ALLAN, AMPACITY!

(Just josh'in ya!)

Did our arctic cold get down to you yet?



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Allan In NE

12-07-2006 11:06:55




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 Re: Checking coils and wiring in reply to Bob, 12-07-2006 08:19:41  
Coldern' Billy He!!, but at least the sun is shinin' LOL

Allan



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relane

12-07-2006 06:51:39




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 Re: Checking coils and wiring in reply to relane, 12-07-2006 06:39:08  
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