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Farmall & IHC Tractors Discussion Forum
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Farmall 400 fluctuaing voltages

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JaredFarmall400

09-03-2006 20:03:43




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Hey everyone,
Went to hook a electronic tach up to my 400 today and it did not work. Following hours of testing I determined that for some reason when I run the tractor the voltage that comes through the system is very unpredictable. My multimeter goes from 2v to 160v's and it all over the place. However, it only does this when the tractor is running. When the tractor is stopped it reads a solid 12.6 volts. I have always had a problem getting this tractor to charge the battery properly, always seemed like the battery was going dead. Thought the voltage problem was releated to the gen. So I unhooked the voltage regulator and the gen belt with the same results. I even tried hooking up a seperate battery to the ignition. The ignition battery showed fluctuatingvoltages and the rest of the sytem showed good. Not sure what is causing this problem, but I can't get the tach to work and I am thinking this is causing the gen to not function properly. The battery is hooked up positive ground and the tractor was converted to 12 volts at one time. Do I maybe need to reverse the polarity to negative ground? Not sure what to do. Any comments appreciated. Thanks

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Jason Archer

09-10-2006 16:43:42




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 Re: Farmall 400 fluctuaing voltages in reply to JaredFarmall400, 09-03-2006 20:03:43  
I put a digital tach on my 400 a couple of years ago and also had problems. My 400 has positve ground and was getting a "double rpm" reading. Wound up switching coils for one with an external resister (the setup on my 350) and wired the tack to that and it worked with no problems since.



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Bob

09-03-2006 23:35:18




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 Re: Farmall 400 fluctuaing voltages in reply to JaredFarmall400, 09-03-2006 20:03:43  
Simply toss your digital meter aside, and use an analog meter.

The electical "noise" produced by the ignition system is giving the meter you are using a "headache", and it's the meter that's coming up with the (false) weird voltages, NOT the tractor.

This is a common problem with using digital meters on these "electrically noisy" old machines.

Dig out an old analog meter, or pick up a new one for probably less than 20 bucks at WaldoWorld, that's plenty accurate for old tractor use, and your strange voltage "gremlins" from the confused digital meter will be gone.

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Jossette

09-03-2006 20:10:53




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 Re: Farmall 400 fluctuaing voltages in reply to JaredFarmall400, 09-03-2006 20:03:43  
the tach will not work with pos ground. your system could be 12 volt pos ground. Should say on the gen or alt



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JaredFarmall400

09-03-2006 20:14:00




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 Re: Farmall 400 fluctuaing voltages in reply to Jossette, 09-03-2006 20:10:53  
The tach said it works with positive ground. I followed the instructions to hook it up and the tach powers on and goes to 0 until I start the engine then the needle is all over the place. I think it is because of the voltage not remaining constant.



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Jossette

09-03-2006 20:22:52




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 Re: Farmall 400 fluctuaing voltages in reply to JaredFarmall400, 09-03-2006 20:14:00  
that would be correct. you need to find that short or switch it to 12 v neg ground. lot less problems and well worth the money.



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Jossette

09-03-2006 20:06:01




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 Re: Farmall 400 fluctuaing voltages in reply to JaredFarmall400, 09-03-2006 20:03:43  
need a new voltage regulator



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JaredFarmall400

09-03-2006 20:09:16




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 Re: Farmall 400 fluctuaing voltages in reply to Jossette, 09-03-2006 20:06:01  
I tried to unhook the voltage regulator and generator belt. With the same results at the ignition. Without the gen hooked up the regulator should not matter correct?



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Janicholson

09-03-2006 20:25:40




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 Re: Farmall 400 fluctuaing voltages in reply to JaredFarmall400, 09-03-2006 20:09:16  
An electronic tach is sensitive to stray voltage (as you have seen). If you are using a digital volt meter, it will not average raw "old iron" voltages very well, a needle type is easier to use on these.
I would do two things.
I would change the plug wires to Magnetic supression wires, (sorensen brand or other quality line) they have real wire in them but it is wound into a coil to suppress the radio noise. (they are very good and do last.)
Next I would use shielded wire for the tach leads and ground the shield. this also keeps stray voltage from the system. A static suppression condenser on the output of the generator to ground will help as well (even an old regular condenser from points will work if it is good)
These will more than likely keep it clean and working like it should. Best of luck, JimN

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Jossette

09-03-2006 20:20:16




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 Re: Farmall 400 fluctuaing voltages in reply to JaredFarmall400, 09-03-2006 20:09:16  
the only thing that can make voltage jump that drastic is a regulator or the starter drawing from the switch from time to time. If it draws that much power while running I would say you have a dead short and the vibrition of the tractor keeps it going. I would say (if the volt meter is accurate) spend some money and switch to 12 neg ground and rewire it before you catch it on fire.



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tn terry t

09-04-2006 04:23:03




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 Re: Farmall 400 fluctuaing voltages in reply to Jossette, 09-03-2006 20:20:16  
you need to rethink what your telling this guy 2volts to 160 volts!!!!! from a regulator????? ??
aint no way thats really happening Jossette try another meter anolog is the best for this old stuff



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Jossette

09-04-2006 06:34:27




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 Re: Farmall 400 fluctuaing voltages in reply to tn terry t, 09-04-2006 04:23:03  
I was figuring on the digital was on the wrong setting and should read 2- 16.0.. Mine did the same thing, replaced the regulator and it is fine.

And, or the meter is completely shot and there is nothing wrong with any of it



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