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New 12V coil, coil says use with resistor

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Bill in Orono,

01-20-2004 17:15:00

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Napa guy says I have to have a resistor in the circuit. Printed on the coil is says "use with resistor" Napa guy said something about coils running on 9-10 vots or something. I have a 300 farmall, now on 12V. I have no idea about the existing coil. It is really rusty.

Please help me clarify the situation.

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Thanks for all the respon

01-21-2004 16:53:20

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

Thankyou

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Doug in OR

01-21-2004 08:28:32

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

Simply stated: If it needs an external resistor, it is not a "pure" 12 volt coil. Some coils are 6 volt; some are 8 volt; some are 12 volt. Fords generally used 8 volt coils on a 12 volt system. They used a resistor wire in series. MOPAR used 6 volt coils with a resistor. Get the real deal. Get a 12 volt coil that does not need an external resistor.

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Mike

01-21-2004 07:17:46

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

Anybody with a IH Scout knows NAPA is about the only store that still has information about the scouts in their books. Once you get a NAPA number you can go anywhere to buy the parts, but why?

You also have to ignore the snot nosed kids working at the counter who ask you if a Scout is made by Toyota.

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Chris C

01-21-2004 05:48:38

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

Why didn't they give you the other coil that has the resistor built in. I just put one on my 460U....I took the old ballist resistor off and got the coil with the resistor already in it. Less wiring and cleaner look. Started right up.

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gene b

01-21-2004 04:57:58

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

If NAPA said you need one then use it. The last one i got from I-H said same thing. If you were using 6v would not need one.

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Alont

01-20-2004 20:04:59

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

Hi Bill
older style 12volt coils and 6 volt coils were manufactured to run on 6 or 12 volts with the primary side coil wound to withstand the constant voltage for which it was designed, I used to have cars and motorcyles with these fitted.
When the engine is being cranked a 12 volt system battery will drop to about 9 volts hence the output at the coil secondary(the plugs) would be correspondingly lower during the cranking. To improve this the manufacturers introduced a coil which was wound with a primary designed to run on about 9 volts.
A resistor was introduced in series(in line) with the coil which dropped the 12volts down to 9 volts at the coil during normal running.A relay operated during the cranking stage to bypass the resistor and provide the full battery voltage to the coil-which would have dropped to about 9 volts whilst cranking.This is the coil,I think, you were offered by NAPA. Hope this helps a little.

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artie

01-20-2004 18:46:49

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

forget about NAPA. Your C-IH dealer has the correct coil.

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Hugh MacKay

01-20-2004 18:33:23

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

Bill: If your going to spend the money on a coil, tell your NAPA man you want one with the built in resistor. Who wants one of those troublesome, ugly looking external resistors on a good Farmall.

You guys in the US seem quite gung hoo on NAPA, they must be a lot better organization to deal with in the US than they are here in Canada. Many times I have been advised on these forums, get it at NAPA; they never have it. I have tried several different stores.

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Paul in Mich

01-21-2004 06:39:59

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Re: Re: New 12V coil, coil says use with resistor in reply to Hugh MacKay, 01-20-2004 18:33:23

Hugh, We here in the states have "First Dibs" on NAPA parts just as you folks have "First Dibs" on the Canadian Club. (I might have said Screech, but only you and I would have known what I was talking about). I find that NAPA's quality is excellent if they have what you want. I was looking for a simple choke cable to replace the kill switch cable on my 40 A, but NAPA's was too good in that it didnt look original. I ended up getting one from the local "Brand X" auto parts store.

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Hugh MacKay

01-21-2004 16:06:22

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Re: Re: Re: New 12V coil, coil says use with resis in reply to Paul in Mich, 01-21-2004 06:39:59

Paul I should clarify, where I find NAPA napping so to speak is really just on tractor parts. I read a lot of discussion on here, a lot more than I take part in. I see you guys talking on items you got from NAPA, for tractors and when I go in here they kind of yawn. I have a feeling someone here in Canada has a distinct advantage over them at the wholesale level, on tractor parts.

I find NAPA quite good on car and truck parts.

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dhermesc

01-21-2004 05:34:17

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Re: Re: New 12V coil, coil says use with resistor in reply to Hugh MacKay, 01-20-2004 18:33:23

Problem is its now about 42 miles to my nearest IH dealer, or 7 miles to NAPA. Chances are I would have to call ahead and wait a couple days anyway since my IH dealer doesn't keep anything in stock - especially for the 60 series and older.

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Hugh MacKay

01-21-2004 16:22:18

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Re: Re: Re: New 12V coil, coil says use with resis in reply to dhermesc, 01-21-2004 05:34:17

dhermesc: Read what I said to Paul and Riverat. It's really just tractor parts I find them poor on here. Seems as though they don't want to bother with them. To be honost with you I believe the problem is the value added Goods and Services Tax we have. Every level along the manufacturing, wholesale and retail chain are carrying that tax on their inventory. I notice this in retail outlets, we don't see the variety on store shelves, that you do in the US. Some bureauacrat dreamed uo this scheme, and it really doesn't affect his income. You people probably have your share of those dudes as well. We just call them non productive people.

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lee

01-21-2004 06:11:38

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Re: Re: Re: New 12V coil, coil says use with resis in reply to dhermesc, 01-21-2004 05:34:17

The IH dealer I like is about 40 minutes from my place. If I know what I want I just call and give them my credit card #. They ship it right to the house.

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riverrat

01-21-2004 04:53:08

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Re: Re: New 12V coil, coil says use with resistor in reply to Hugh MacKay, 01-20-2004 18:33:23

Hugh, sounds like you have some rotten stores around you. My local NAPA is great. The guys are helpful, polite and knowledgable. It's too bad you don't have a good one nearby because they are a godsend when working on machinery, etc.

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Hugh MacKay

01-21-2004 15:54:56

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Re: Re: Re: New 12V coil, coil says use with resis in reply to riverrat, 01-21-2004 04:53:08

Riverat: I prpbably should clarify, I find NAPA quite good on car and truck parts. They just don't seem to carry any tractor parts. Many of the items I see you guys talking on going to NAPA for, they just don't seem to carry here in Canada. I do apologize I should have make myself clearer.

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42FarmallH

01-20-2004 19:19:24

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Re: Re: New 12V coil, coil says use with resistor in reply to Hugh MacKay, 01-20-2004 18:33:23

NAPA really stinks on most things here, but for a very few things they are OK. Customer service is so-so, as good as other parts stores in town. They are the only ones that will overnight me gasket sets for vehicles when I really need them. Only store open on Sunday too.

I guess overall they are OK, but some things really stink there and leave a bad taste in my mouth for quite awhile...

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Van

01-20-2004 19:05:50

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Re: Re: New 12V coil, coil says use with resistor in reply to Hugh MacKay, 01-20-2004 18:33:23

Hugh, NAPA is a great deal on some things. Bought a carb kit for a 300 at NAPA, found a another on the shelf in the shop my dad had bought from IH and not used, same exact kit, 1/3 the cost. Just bought a new coil for my British built 354 utility tractor, The correct coil was $28.00, put a chevy coil on for $7.82. Aint nobody gonna know but me after I paint it red.
Van

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Brad L

01-20-2004 18:13:40

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

I think if your coil needs a resistor tell the napa man to give you a ballast resistor from an old chrysler product and you will be fine.

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Nebraska Cowman

01-20-2004 17:23:52

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Re: New 12V coil, coil says use with resistor in reply to Bill in Orono, MN, 01-20-2004 17:15:00

there is no such thing as a 12 volt coil. all coils are 6 volt, some have the resistor built in and others need an external resister to use with 12 volts.

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Hugh MacKay

01-20-2004 18:41:02

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Re: Re: New 12V coil, coil says use with resistor in reply to Nebraska Cowman, 01-20-2004 17:23:52

Cowman: Interesting, my Farmall 130 has a coil with lettering right on the side 12 volt coil, no external resistor required. The coil came from CaseIH here in Canada. I made note of what was written on the coil this afternoon as I was installing a set of points.

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twopop

01-20-2004 20:29:45

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Re: Re: Re: New 12V coil, coil says use with resis in reply to Hugh MacKay, 01-20-2004 18:41:02

cowman is correct as farm as coils for point ignition is concerned.oem electronic ignitions use true 12 volt coils

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Paul in Mich

01-21-2004 06:48:50

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Re: Re: Re: Re: New 12V coil, coil says use with r in reply to twopop, 01-20-2004 20:29:45

Folks, I'm by no means an expert on the subject, but in scanning through the O.E.M. catalog, I see a separate part number for a 6 volt and a 12 volt coil. Could they be the same coil except that the 12 volt has a built in resister and the 6 volt does not?

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Doug in OR

01-21-2004 13:02:31

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Re: Re: Re: Re: Re: New 12V coil, coil says use wi in reply to Paul in Mich, 01-21-2004 06:48:50

It probably has an internal resistor. If you double the primary windings, you increase the inductance. In my mind, this would require a larger condensor to compensate.

The real way to know if your coil is set up for 12 volts is to measure the resistance across the two studs on the coil. A 12 volt coil will have approximately 3.2 ohms. A 6 volt coil will have approximately 1.5 ohms. Yes, you need a fairly accurate ohm meter to do this. You also want to ensure that you have a good connection where your leads are contacting the studs.

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Greasy John

01-20-2004 19:49:20

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Re: Re: Re: New 12V coil, coil says use with resis in reply to Hugh MacKay, 01-20-2004 18:41:02

Hugh I think you will find that "no resistor needed" means its already built inside with the windings. John

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Hugh MacKay

01-21-2004 01:14:37

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Re: Re: Re: Re: New 12V coil, coil says use with r in reply to Greasy John , 01-20-2004 19:49:20

John: I know that, I'm just reading what is printed on coil. They are calling it a 12 volt coil.

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49 Cubber!

01-20-2004 18:27:02

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Re: Re: New 12V coil, coil says use with resistor in reply to Nebraska Cowman, 01-20-2004 17:23:52

I never heard that!I have a coil on my M that has USE EXTERNAL RESISTOR on it and I dont have a resistor on it and its been that way for years.I always thought that was on there in case you wanted to drop the voltage or something.I havent burned up but one set of points in quite some time on it either.????? ????Beats me.

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Greasy John

01-20-2004 19:46:08

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Re: Re: Re: New 12V coil, coil says use with resis in reply to 49 Cubber!, 01-20-2004 18:27:02

49 your M must be 6 Volt system?? and you wouldn't need the resistor BUT if you run 12 volts you just got lucky! John

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49 Cubber!

01-21-2004 12:27:39

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Re: Re: Re: Re: New 12V coil, coil says use with r in reply to Greasy John , 01-20-2004 19:46:08

Nope,12 volt battery in it,12 volt alternator,12 volt coil.NO resistor at all,unless the guy sold me one with a built in resistor and didnt tell me!Dont recall telling him or him telling me either way! Ido know it had/has Use with external resistor on it.J ust thought that meant if you wanted to or it wasnt built in.guess I did get lucky!

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