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Tractor Talk Discussion Forum

Diode in alternator system

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Bret4207

03-05-2005 06:57:38




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What kind of diode do I need and where does it go in an updated to alternator charging system? I have several tractor the trickle down while sitting and assume this is due to a lack of the diode. Thanks




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Bret4207

03-06-2005 05:06:09




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 Re: Diode in alternator system in reply to Bret4207, 03-05-2005 06:57:38  
Thanks to all, the biggest problem I have at the moment is with a 444 Bobcat with a Motorola alt. I thought I had the wires hitched right but will go back and check. There isn't much room for a bigger alt on the old Bobcats and I'd like to stick with the Motorola if I can.

George- Where are you in NY? I'm near Ogdensburg.



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J. Schwiebert

03-06-2005 13:10:50




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 Re: Diode in alternator system in reply to Bret4207, 03-06-2005 05:06:09  
Motorola did use an isolation diode. At least they did when they were on the Molines. I gues I should look at our 4020 and see if there is one there.



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jdemaris

03-06-2005 11:13:50




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 Re: Diode in alternator system in reply to Bret4207, 03-06-2005 05:06:09  
If you want to use an alternator with the same hookup as a Delco 10SI or 12SI, the 60 amp Hitachi alternators from the older Subaru Loyales - 1995 and older work great. They are much smaller and compact than the Delcos. They are also more reliable. I pick them up for $15 apiece at my local junkyard. They're cheap because they rarely go bad and thusly bad sellers. There is even a smaller one on the Subaru Justys that's still rated at 60 amps - but they're a little harder to find - especially in New York where everything rots out in ten years from road salt. I used one on my Cletrac HG with space is limited. I've got property near you - in Malone and also some woods on the Jefferson-Lewis County border. They even salt the dirts roads there in summer. I've gotten stuck behind a brine truck once or twice in the middle of August. I live in Otsego Co. - more hilly and less windy than Ogdensburg but just as cold - and I don't have a big river to play in (along with the Canuks). I'm 15 miles from Cooperstown - and the guy that founded the town originally (Judge Cooper) also went up your way and founded Gouverneur.

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George S. in the real NY

03-05-2005 17:44:51




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 Re: Diode in alternator system in reply to Bret4207, 03-05-2005 06:57:38  
Some years ago, when the 10SI alt was new to the world, I was told by folks in the auto parts biz that that alt always had a slight current draw. Not bad enough to notice when you took your mark of excellence out on the road every day or so. But if you were going to park it for a few months, like a camper over winter, you should unhook the battery to prevent slow drain. Thus, I like the early GM alt with the external regulator which does not have said probie. That is what I put on my 720 JD back in '86 and have not had battery drain problem and it sits idle for months especially in winter. That did require a diode in the wiring, too. Can anyone else confirm this info about current draw all the time on the 10 SI?? My 2 cents

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jdemaris

03-05-2005 20:11:00




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 Re: Diode in alternator system in reply to George S. in the real NY, 03-05-2005 17:44:51  
I've heard such complaints but haven't seen it on a good alternator. Most alternators have an isolation diode built into them (or a set of them) at the output. Delco 10SI and 12SI also have a diode-trio that sometimes fails. On any and all the machines I've worked on that had a complaint about slow battery draw down, if the alternator was causing it, it had a bad diode. I've also seen a few that were wired wrong, and the drain was caused by the field left energized all the time. That's not an alternator problem. Also worked on a few cars and trucks with similar complaints, put a milliampmeter on them, and found the draw being caused by things like electic clocks or radio memory chips that are energized all the time. I'm in the habit of checking any alternator that I install, it's easy, just hook a milliamp meter to it and check for draw. A simple amp meter does not read low enough. If a diode is bad at the isolation-output end of the alternator, it will draw batteries down. If if has bad diodes at the rectifing bridges, then is will have low ouptut. I've got several tractors, backhoes, and crawlers that sit all winter without being run, and they all have Delco alternators on them - and I have no problems with current draw when sitting.

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Joe (Wa)

03-05-2005 20:56:15




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 Re: Diode in alternator system in reply to jdemaris, 03-05-2005 20:11:00  
You can go low tech on this thing for a quick check. Disconnect the neg (or pos) battery terminal, series a 12v light between the battery cable and the neg post. Use an indicator lamp or other bulb 1 amp or less. If the lamp lights full bright you know you are leaking current at the amp rating of the lamp or more. Takes many days at 1 amp or less draw to run down a 600-800 AH battery. If the lamp doesn't light the drain down problem is in the battery, low alt output, or your run time is not long enough to recover the battery from starting and normal run use.

If the lamp is lit, isolate unswitched terminals first as close to battery source as you can till the light goes out. If lamp is still on, lift the power-in terminal on switches. Lamp still on, you've got a leak to gnd between the battery and the terminals that you have lifted, may be a skinned wire rubbing on the frame, etc.

There can be 2 of more leaks to gnd with enough current to keep the lamp lit, so leave all terminals lifted until the lamp is completely out. As you connect the terminals back up keep an eye on the lamp.

Joe

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john in la

03-05-2005 17:57:12




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 Re: Diode in alternator system in reply to George S. in the real NY, 03-05-2005 17:44:51  
Yes a 10SI that is hooked up correctly will draw down a battery but it takes months not days. A weak or half dead battery may over emphasize this problem.

I never did like to let a engine sit for months with out starting even if it was just to run in place for a while to lube every thing so I guess that is why I have never had a problem with this.



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john in la

03-05-2005 17:24:11




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 Re: Diode in alternator system in reply to Bret4207, 03-05-2005 06:57:38  
Bret;
If you needed a diode you would know it long before the battery went dead from a discharge problem. You would not be able to shut off your tractor if you needed a diode.

The #1 or F plug on the alternator gets hooked to the terminal block key on side. It only gets power when the key is on. The problem is on a gas engine the coil also gets hooked to this same spot. When you turn off the key to cut power to the coil and kill the motor you get a back feed from the spinning alternator which keeps the coil firing so the engine will not kill.

GM used a idiot light in this wire to break the backflow. Since some tractors do not have a place for this dash idiot light another way of doing it is ti install a one way diode in this wire. This allows you to supply power to the alternator to energize the field but stop the backflow to the coil.

I think your problem is you have something wired wrong. I may be out on a limb here but since all your conversions do the same thing I suspect that you have the #1 wire hooked to power all the time and not hooked through the key. This will drain the battery for sure.

While This wiring diagram is for a Ford it should get you on the right page to see if you have it wired correctly.

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Jerry L /AZ

03-05-2005 14:12:59




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 Re: Diode in alternator system in reply to Bret4207, 03-05-2005 06:57:38  
if you are useing a delco 10-si alt the #1 spade goes to the terminal block the diode goes in this wire the diode you can get at radio shake for about a buck part #in 4oo3 the cathode end or the end that has the silver band goes toward the alt. you will also need a coil with the built in resistor since the voltage reg is built into the alt you no longer need the old voltage regulator and like wise since the resistoe is built into the coil you no longer the ballast resister
hope that helps you ....Jer

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jakej

03-05-2005 07:52:37




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 Re: Diode in alternator system in reply to Bret4207, 03-05-2005 06:57:38  
The diode is available from Genesee.com who has conversion kits and is shown in the article section of research & info to the left. I hook up my P1 to the ign switch to cut any drain on the battery. Also nseries.com has the wiring it's for a ford but it applys to all conversions. The article mentioned above is named "Upgrading the Oliver 55 electrical system"



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Jon H

03-05-2005 13:35:16




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 Re: Diode in alternator system in reply to jakej, 03-05-2005 07:52:37  
The diode is used on a gasoline engine converted to a Delco 10-12SI alternator. It is only used to prevent a backflow of power from the alternator's #1 exciter terminal to to the ignition coil,when the ignition coil and alternator exciter wire are connected to the same ignition switch terminal. It will do nothing for a slow electrical drain when the machine is parked. You need to find and repair the offending electrical device causing the drain.

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Allan in NE

03-05-2005 13:49:02




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 Re: Diode in alternator system in reply to Jon H, 03-05-2005 13:35:16  
Jon,

You mean like a drain from a leaky diode? :>)

Allan



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Jon H

03-05-2005 18:45:37




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 Re: Diode in alternator system in reply to Allan in NE, 03-05-2005 13:49:02  
Yep Allen,thats a good spot for a first look. The rectifier assy in those Delco alts like to collect brush dust and other semi conductive crud between the rectifier heat sinks or between the pos heat sink and the case to make a slow drain. And then there is the chance of a partially shorted positive button diode in the rectifier assy.



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