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Bad alternator?

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Michaels Dad

12-29-2007 09:06:03




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I need some education on alternators please.

My 640 has been converted. Still has the 6 volt coil with resister. Normally when the key is turned on it shows battery voltage on the voltmeter. When started it would show 12-14 volts even at idle.

A few days ago the meter would not show voltage when I turned the key on, but then would show it after start up or higher revs. Sometimes it would show 12 volts when running and then would jump to 14 or so.

Went through all the wires I could find, replaced ends etc. with good results, but still not consistent, but would start charging with higher revs.

This morning the meter will not get off bottom even at higher revs.

Here’s what I’ve done so far to see if the regulator or alternator is bad.

Pulled the ground cable off the battery while running, engine quit.

Disconnected the wire coming off the rear of the alternator while running, it showed 0 voltage.

If it looks like a duck, quacks like a duck….well you know the rest. But being almost 30 miles from a parts house (that can’t check the alternator) and only 4 days left before I have to get back to the city is it kind of safe to assume I have a bad alternator, or could it be something in the wiring.

I’ll continue to use the tractor this way, and I’ll put the charger on the battery at night.
Next move would be to bring the alternator back to the city with me to get it checked, but if someone thinks I have another problem I’d like to check that out before I leave.

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Michaels Dad

12-30-2007 09:56:31




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 Re: Bad alternator? in reply to soundguy, 12-29-2007 09:06:03  
Don't you just love it when things fix themselves? Fired the 640 this am, temp about 42, volt meter came on with the key, held 12v until I reved it, then showed 14v. Leaving it alone for now, don't know what happened there.

Then the proof meter quit working. Found the drive from the pump was worn out where the eared drive piece slides in. Was able to squeeze the end together enough to getting driving again.

Life was good.....well that didn't last long. Wife called me from home 300 miles away to tell me she was mowing the lawn and hit the water line coming into the house and water was blowing everywhere. Of course she didn't know if it was the house water or the sprinkler system water since they are different meters. She finally got a neighbor to come over, figure out which meter to turn off and survey the damage. Outlook was good, she said she could cut the PVC and install a coupling.

Now if I could figure out why my cordless drill won't work on variable speed my day will be complete.

Life is good in Utopia, TX..... at least for now.

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trucker40

12-29-2007 13:59:36




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 Re: Bad alternator? in reply to Michaels Dad, 12-29-2007 09:06:03  
Lots of times stuff quits working in cold weather,then starts working again when it gets warm.Lines leak oil,gas,antifreeze when its cold,not when its hot.Sometimes its the other way.Voltmeter probly dont like cold weather,went on vacation till it gets warm again.



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Michaels Dad

12-29-2007 12:08:21




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 Re: Bad alternator? in reply to Cvan, 12-29-2007 09:06:03  

JF in CT said: (quoted from post at 20:07:44 12/29/07) Sounds like you may have a bad connection supplying power to the voltage regulator (external or internal)when you turn the key on so that there is no power being supplied to the alternator field coil. Its also a long shot that the alternator brushes are sticking.

Jim


Only have two wires on the alt. One is the insulated post, and the other is a ground with the wire leading up the wire loom.

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Michaels Dad

12-29-2007 12:02:57




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 Re: Bad alternator? in reply to Cvan, 12-29-2007 09:06:03  
Just put a hand held meter and 12v test light across the two wires feeding the voltmeter, both showed voltage with the key on.

Took the meter out, hooked it up directly to the battery and it didn't move. You don't really look for a 5-6 old brand new voltmeter to crap on you.

Still doesn't answer the question as to why I showed no voltage coming out of the back of the alt. and why the motor quit running when I disconnected the battery.

The battery shows 12.6v, and when I hooked the wire back to the alt. it showed 14.7v at idle, so I guess the alt is OK, but the new meter is bad.

Those "queertrons" eat me up every time.

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Bob

12-29-2007 12:15:48




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 Re: Bad alternator? in reply to Michaels Dad, 12-29-2007 12:02:57  
It's best NOT to disconnect the battery OR the alternator wire while the engine is running.

Sooner, or later, the resultant voltage spike will short out the voltage regulator or the rectifier diodes, ultimately letting all the smoke out of the alternator.



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JF in CT

12-29-2007 11:07:44




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 Re: Bad alternator? in reply to Michaels Dad, 12-29-2007 09:06:03  
Sounds like you may have a bad connection supplying power to the voltage regulator (external or internal)when you turn the key on so that there is no power being supplied to the alternator field coil. Its also a long shot that the alternator brushes are sticking.

Jim



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Bob

12-29-2007 10:42:54




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 Re: Bad alternator? in reply to Michaels Dad, 12-29-2007 09:06:03  
You need to get a hand-held voltmeter on the battery, and see what's going on before tearing the alternator off/throwing money at the problem.

If the tractor is still cranking and starting, it would seem there is still 12+ Volts in the battery, and the dashboard voltmeter should be showing this.

If the hand-held meter is showing voltage within the range of the dahboard unit, and the dashbaord unit is still "pegged" at the bottom, you have a bad voltmeter, or the meter is not properly grounded, or there's something wrong in the wiring to it.

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