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Farmall & IHC Tractors Discussion Forum
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1947 BN / alternator carb question

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Josh in Maine

11-16-2007 00:15:46




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Couple of questions: Last weekend, I bought a 47 BN, been working on it nights & got it running good. I have a question about an alternator that was added. The alt has a single post in the rear, there is a wire coming off that post & goes to one side of an amp meter in the gage box mounted on steering post, on the other side of the amp meter, I have a wire that goes to the starter connection. From that starter connection, there is the battery cable going to the + side of my 12v battery. Is this o.k.? My alt is putting out 14.4V DC, won't this damage my 12v battery? The only variable is that they jumpered off the amp meter post to a switch that controls the 2 headlamps & rear worklight, so, if I leave my lights on, it drags the voltage down coming off the alt. Second question is about the carb, everything is hooked up properly & my throttle is working well the advance, but, it doesn't idle down w/o getting off the tractor & manually giving the linkage a little tug. Should I have a return spring on the carb? Or is my governor sticky & I need to lube it? Thanks from the coast of Maine!

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Bob M

11-16-2007 12:19:04




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 Re: 1947 BN / alternator carb question in reply to Josh in Maine, 11-16-2007 00:15:46  
One of the disadvantages of a “single wire” alternator as have on your BN is the voltage drop under load. This is especially true if the wiring between the alternator output stud and battery + is undersized.

(A traditional 3-wire alternator properly connected incorporates a sensing wire separate from the current output lead. This permits the internal regulator to compensate for the voltage drop that occurs in the output lead under heavy current load - such as when your lights are on.)

However as Brownie suggests below, as long as voltage at the battery is greater than 13.6 volts or so with the engine running and the lights on it should be OK.

----

PS - If you happen to see my baby sister in Brunswick wish her a happy 50th birthday!!

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ScottyHOMEy

11-16-2007 09:19:15




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 Re: 1947 BN / alternator carb question in reply to Josh in Maine, 11-16-2007 00:15:46  
HAve you got the rod on the left side from the governor to the carb adjusted? Engine off. Throttle control all the wya forward. Pull the clevis pin at the front of that rod. Holding the rod all the way back and holding the governor arma s far toward the rear as it will go, adjust that clevis on the thread until it lines up and replace the pin.

It maya lso be one of the needle bearings someone mentioned down below.

I' check these things out before going into the governor.

Whereabouts on the coast? I'm just past Belfast.

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Josh in Maine

11-16-2007 12:50:42




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 Re: 1947 BN / alternator carb question in reply to ScottyHOMEy, 11-16-2007 09:19:15  
Kennebunk



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El Toro

11-16-2007 06:47:49




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 Re: 1947 BN / alternator carb question in reply to Josh in Maine, 11-16-2007 00:15:46  
That's a good charging voltage for a 12 volt battery. You had better have that on your car or truck too. You need that to keep your battery fully charged. Hal



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John T

11-16-2007 05:58:37




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 Re: 1947 BN / alternator carb question in reply to Josh in Maine, 11-16-2007 00:15:46  
Josh, The alternators main output stud/terminal indeed wires to the LOAD (NOT Battery/Starter) side of an ammeter while its other SUPPLY terminal is fed voltage from the hot ungrounded battery post often via a wire to the starter switch where the big battery cables attaches...

Next, loads like lights and ignition (if its a coil ignition instead of a mag) should also be fed from the ammeters LOAD terminal which is the same terminal where the alternators output is connected.

As far as voltage, that 14 and over range is typical of what many alternators will raise battery voltage to, so unless the battery boils over and/or outgasses badly Id not worry for now.

John T

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Brownie450

11-16-2007 03:44:00




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 Re: 1947 BN / alternator carb question in reply to Josh in Maine, 11-16-2007 00:15:46  
The governor problem could be caused by a needle roller bearing in the "long arm" of the governor. With age, these bearings tended to get a small amount of moisture from crankcase vapors [blow-by, cold weather] & tended to rust & "drag" on the governor shaft which controls the throttle plate. These parts are still available from IH. If the throttle rod adjustment doesn't correct the problem, have a go at the governor. As far as the alternator voltage dropping with lights on, as long as it doesn't drop below 13.6 to 13.8, I wouldn't worry. If it's much less, You probably have 1/3 or 2/3 of the diode trio open. Easy to replace.

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Bob

11-16-2007 01:41:36




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 Re: 1947 BN / alternator carb question in reply to Josh in Maine, 11-16-2007 00:15:46  
1.) A "12 Volt" battery is VERY comfortable being charged at 14.4 Volts.

2.) An alternator of any common size SHOULD keep up with 2 or 3 lamps without the charging voltage dropping much.

3.) To solve the "doesn't idle down" problem, the linkage rod between the governor arm and the throttle lever on the carburetor needs to be adjusted for LENGTH according to the procedure in the service manual. If that doesn't solve the problem, an OH of the governor is indicated. You DO NOT need a "return spring" on the carburetor's throttle lever.

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