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| montana charlie Report to Moderator
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Howdy folks,
I have searched this forum for what I need (over 600 threads) and the few discussions which seemed be right no would no longer supply 'the image'. I have an 871 SOS which uses a generator light...no ammeter...and can't find a wiring diagram for this setup. I have just installed a 6 volt, positive ground alternator, and do not want to modify the existing wiring harness...but I am willing to reroute the wires. The alternator is a 'one wire' job, but I want to use it as a 'three wire unit' and incorporate the dash light. Anyone able to help me locate this version of the Ford wiring? All others have the ammeter. Thank you for your attention... | | [Log in to Reply][No Email] | |
| Bob Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 12:40:59 | | Typically, one side of a generator "idiot light" is connected to a power source that shuts off with the ignition switch, and the other side of the "idiot light" connects to the "A" (armature) terminal of the voltage regulator (or the "A" terminal at the generator). Find this wire, and touch it to a good ground with the key on. The idiot light should light while it's shorted to ground. Take that wire and connect it to the #1 terminal on your alternator, and, providing your one-wire regulator can handle that, that should do the job for you! The original 12 Volt regulators in the 10SI Delco were designed around using a #194 indicator light, not sure what would be appropriate to use on your 6 Volt system! You sure must not mind paying a premium price to have a special alternator like this built up when an of-the-shelf 12 Volt negative unit is so cheap and easy to get! | | [Log in to Reply][No Email] | |
| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to Bob, 01-16-2005 18:10:01 | | In order to answer each of your points, Bob, I will insert comments into a copy of the text of your post. Bob..."Typically, one side of a generator "idiot light" is connected to a power source that shuts off with the ignition switch, and the other side of the "idiot light" connects to the "A" (armature) terminal of the voltage regulator (or the "A" terminal at the generator)." Judging from the 12 volt Deisel diagram which I intend to use (I didn't have it when this thread started), I believe you are correct. Bob..."Find this wire, and touch it to a good ground with the key on. The idiot light should light while it's shorted to ground. Take that wire and connect it to the #1 terminal on your alternator, and, providing your one-wire regulator can handle that, that should do the job for you!" Disconnecting that wire and grounding it is a simple test which has (up to now) eluded me. There is a good ground about an eigth of an inch to the left of that A terminal. I guess I was just expecting to have a tough time. Thanks for that input, Bob. Bob..."The original 12 Volt regulators in the 10SI Delco were designed around using a #194 indicator light, not sure what would be appropriate to use on your 6 Volt system!" I am assuming that the existing 6 volt light in my dash will be suitable. Time will tell. Bob..."You sure must not mind paying a premium price to have a special alternator like this built up when an of-the-shelf 12 Volt negative unit is so cheap and easy to get!" I dunno, Bob. I haven't really added up all of the costs of a 12v alternator, 12v battery, 12v starter (eventually), and all of the small parts required. When my generator died, I wanted to replace it with an alternator because they're more efficient...but not change the whole electrical system.
The only 12 volt accessory I wish I could use is a cigarette lighter...but I'm trying to quit, anyway. My alternator cost more, for sure, but since I welded up my own bracket, that price is the total cost of the conversion. I won't claim that this mod is cheaper (it might be), but it sure is easier to do. There is also this to consider...the necessary parts are readily available on eBay. A $5 Delco core from a junk yard could be built into the same one I bought, for around 60 percent of what I paid. | | [Log in to Reply][No Email] | |
| Bob Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-16-2005 19:56:31 | | We got into the "generator idiot light" hookup thing over on the Farmall Board a month or so ago. They're hooked up more or less the same way. I'm "multi-tractoral", so I lurk here from time to time, too. If the "idiot light" you use is of too high a wattage, and the tractor is gasoline powered, enough current will backfeed from the alternator #1 terminal to power the ignition system with the key "OFF", and prevent it from shutting off. | | [Log in to Reply][No Email] | |
| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to Bob, 01-16-2005 20:07:38 | | The FARMALL board!!?? I thought those Farmalls were coal powered! :-) |
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| Dave (IL) Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 12:40:59 | | Isn't the alternator idiot light dependent on the three wire installation? |
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| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to Dave (IL), 01-16-2005 14:29:04 | | You are correct, Dave (IL). An alternator with a 'one wire' regulator in it (6 volt or 12 volt) will start to charge based strictly on engine RPM, whereas a 'three wire' actually needs the resistance of that light bulb to develop the 'start charging now' signal. Mine is a 'one wire' alternator, and it charges nicely by by simply connecting the output to the battery. But, my idiot light comes on when the ignition switch is turned on, and stays on all of the time.
I know the battery is charging because the light gets a little dimmer when I shut off the engine and the alternator stops spinning. Any 'one wire' CAN be hooked up as a 'three wire'...which is what I intend to do. The light needs to be connected to P1 on the alternator, and the other side of the light (simplyspeaking) gets connected to the cold side of the ignition switch. That way... When the switch is turned on, the light comes on because of getting voltage through the switch. When the voltage at P1 of the alternator jumps to the same level (because it started charging) the light goes out. This could be done by simply connecting the other side of the light to the ignition switch (or even the coil), but would require cutting the existing wire away from the original harness. I prefer to find the other end of that wire and use that to make the connection without making any 'permanent' change to the original wiring. I believe (now) that it is available at one of the terminals on the old voltage regulator.
If true, I plan to use the V/R terminals as the connection points for three short jumpers to make things hook in where needed. That way, the three leads that came off of the generator will be connected to the three alternator terminals, but will have slightly different new jobs. Pull the jumpers and reconnect the wires to the original V/R terminals and Bingo!...it's back to the factory configuration. It all sounds good in theory...Tuesday will be the test if the weather cooperates. | | [Log in to Reply][No Email] | |
| Dave (IL) Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-16-2005 15:27:06 | | I see some of the confusion now. When you said you were going to use your one-wire as a three-wire it seemed like you meant "external" to the alternator. What you were really saying is you were, in effect, modifying your one-wire to three-wire. On the DC genny, you have the added functionality of the regulator turning off the connection between the bat and gen/arm wires from the genny as the rpm drops. This isolates the idiot light and the ignition. Couple of common problems encountered are the engine running on because it's still getting current from the alternator throught the idiot light. Also enought current to slowly drain the battery. I'm not expert on this, just observing, so I'm not adequately explaining it. I believe some of the solutions involve picking the right idiot light and/or installing a diode. | | [Log in to Reply][No Email] | |
| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to Dave (IL), 01-17-2005 09:02:57 | | Dave (IL)..."What you were really saying is you were, in effect, modifying your one-wire to three-wire." You got it, now, Dave...sorry I wasn't clear enough in the beginning. Dave (IL)..."Couple of common problems encountered are the engine running on because it's still getting current from the alternator throught the idiot light." Boy! You must have been at this for a while, Dave, 'cause you have gathered up a basketful of information on this subject. I haven't had that problem, yet, but I got the impression (somewhere) that the 'running on' was actually caused by residual voltage from the alternator reaching the coil, which is on the the cold side of the ignition switch 'along with' the alternator's 'sensing' lead. Adding an idiot lite (where one did not exist) is supposed to break that cycle which keeps re-energizing the coil because, as it flashes, the bulb 'soaks up the current' and let's the coil shut down. Dave (IL)..."Also enought current to slowly drain the battery." This one I HAVE had some experience with. I couldn't understand why the battery in my Hesston swather would slowly discharge. I decided the alternator (a Delco unit in a machine with a Chrysler engine) was probably not original...so I started tracing the hook up wires. It is a 'one-wire' alternator that was hooked up as a 'two wire' which allowed the ammeter to get a reading. But, that meant the alternator circuitry was always connected to the battery...providing a high resistance path to ground...which allowed the slow drain. I changed it to a standard 'three wire' hook up (had to add another wire to the harness) and added a dash light and the problem was cured. Maybe I could have just connected Wire 2 to a different side of the ignition switch, but that dash light is handy when you need something that says, "Hey Dummy! You left the ignition on... again!" | | [Log in to Reply][No Email] | |
| Dave (IL) Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-17-2005 09:49:14 | | Sounds like you have your arms around the pieces of the problem. I haven't had the need yet to really think through the alternator setups. As for being at this for "a while", I had to shut down a 20 person development group last year, including me :) Since then I'm kinda between jobs or in early retirement. I'm spending WAY too much time reading this tractor forum off and on all day. Studying techology and learning from others is basically what I've done for 35 years and this is just another technology. Sure is fun though. Anybody out there in the Chicago W or SW burbs need a good PC developer/manager? (now I'll be in trouble :) ) | | [Log in to Reply][No Email] | |
| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to Dave (IL), 01-17-2005 10:23:32 | |  I have finished my alternator modification and have a created a wiring diagram for using all three alternator terminals...on a tractor which includes a factory installed charge indicator light. A little explanation is in order... Unfortunately, the two red wires on the A terminal of the voltage regulator are crimped into a single spade connector. Therefore the small wire will have to be clipped loose to connect it to the white wire removed from the v/r F terminal. The black lead from P2 on the alternator is best tied into the line from the Terminal Block to the Starter Relay by using a short jumper over to the cold side of the Terminal Block All three leads connected to the alternator are the same leads which came off of the generator...but you will have to make 'em a little longer. I used the 12 Volt Deisel diagram to make this one up, and the wiring will work for my 6 volt mod OR a 12 volt alternator modification. (I hope the 'picture' loads in properly. If it doesn't, it's in the Galleries under Parts and Pieces.) Any questions? | | [Log in to Reply][No Email] | |
| john in la Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-16-2005 15:27:06 | | | If you know all this then why did you ask for the wiring diagram in the first place.
Get a ohm meter and you can trace the wires with out cutting the caseing open. |
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| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to john in la, 01-16-2005 16:00:59 | | john in la..."If you know all this then why did you ask for the wiring diagram in the first place?" Guess you 'had to be there', John.
When this started, I knew what the alternator needed...but, before finding the 12 volt Diesel diagram, I didn't know how the tractor could provide it. I've heard about your good reputation...thanks for the input. |
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| Dave (IL) Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 12:40:59 | | Don't mean to sound churlish here, but think about what you're asking. Nobody else here knows what Dave sent you so it's a little difficult to know what it is you're missing. There is no such thing as a "standard" conversion to alternator. Most of them involve going from 6 to 12 and changing polarity from pos to neg. But they all are DIFFERENT because each person did it their own way and there is no "standard". Even with that there are a lot of common components and the "collective" here can usually make sense of them. You have chosen to come up with a very "one off" solution. Even if I was a EE, which I'm not, I could only speculate on the wiring requirements of your very custom implementation. Idiot lights for DC generators operate very differently than idiot lights for alternators. If you find the red wire, do you know where to hook it up to make your idiot light work? I know there are wiring diagrams out there that show the genny idiot light without an ammeter. You should be able to see where the wires from the idiot light on the genny go and deduce which is red and where it goes. Then go check the harness at that point and you should see the red wire coming out. It just seems like you have a solution that may be clever, but is very unusual, and your crabbing at this forum because nobody is jumping right in with an answer to the "rest of the problem". "The alternator is a 'one wire' job, but I want to use it as a 'three wire unit' and incorporate the dash light". There is no "standard" Ford wiring diagram that's going to tell you how to do that. And if there is, somebody is bound to jump in and tell me I'm an idiot, so you'll still get what you need :) PS - John in la is pretty good at this stuff. | | [Log in to Reply][No Email] | |
| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to Dave (IL), 01-15-2005 21:49:47 | | Now, Dave(IL) said,
"Don't mean to sound churlish here, but think about what you're asking." Well, sir, what I asked for was a diagram of the original wiring for a Ford 871 (Select-O-Speed) that comes with a generator light instead of an ammeter. Nothing more. If you'll change your mind about me sounding like I was 'crabbing', I'll promise not to think of you as 'churlish'. |
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| Dave (IL) Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 23:50:10 | | | I accept your gracious offer and apologize to you and the forum for my burst of churlishness. |
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| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to Dave (IL), 01-16-2005 08:06:16 | | The hatchet is happily buried, Dave(IL). I admit that I was little too 'wordy' (don't talk to many humans out here) which camouflaged the simplicity of my original request. But, at the risk of wasting forum storage space, I want to expound just a little more on this style of 'conversion'...in case others are interested (plus, I'm a little 'too proud' of myself). Most (maybe all) of the 12 volt conversions use the Delco 10-SI alternator.
The kind you get from an automotive parts house are pretty cheap (about $30), but they need a three wire hookup to function right, unless you buy the (more expensive) marine alternator. It costs a little more for a 'one wire' Delco because the voltage regulator has been replaced to get it to charge with 'no signal' on P1, and to shut down the charging circuit without an input on P2. Then (in the 12 volt conversion) you have to change polarity (where needed) throughout the tractor, add a ballast resistor, and switch out many of the 6 volt components...and buy a battery.
Eventually, the starter will probably need to be changed, too, even though it WILL work at 12 volts...for a while. A regular old Delco 10-SI, modified to work at 6 volts and use a positive ground, eliminates ALL of the 'extra changes'. For about $85 and a bracket to mount it, the whole job takes an hour, or so.
Just connect the alternator's Bat terminal to any lead that goes to the battery's negative post. If your generator has died or you just want the reliability of an alternator, and don't need to run 12 volt accessories, this conversion is a snap. If you have my luck...and have an idiot light which you want to be useable...then the wiring gets more complicated.
But, I am positive that it can be done simply...with no damage to the original harness. When I figure that out, I'll be happy to share the knowledge. | | [Log in to Reply][No Email] | |
| Jim.UT Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 12:40:59 | |  This is the best I can do. It's an original diagram for a 6 V system, but it has the ammeter in it. |
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| Jim.UT Report to Moderator
| Try this one in reply to Jim.UT, 01-15-2005 21:36:13 | |  Here's the diagram for the 12V diesel tractors. It shows the idiot light and a red wire from the generator. This is probably closer to what you're looking for. |
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| montana charlie Report to Moderator
| Re: Try this one in reply to Jim.UT, 01-15-2005 21:40:51 | | Jim.UT,
Thank you for you effort. I happened to find that 12 volt Diesel diagram a little earlier, and agree with you that it might be the closest I will find. It's a little cold out to be messing with a tractor (-20), but it's supposed to be warmer on Tuesday. That's when I'll see if it's close enough. Thanks, again, Jim. |
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| Dave (IL) Report to Moderator
| Re: Try this one in reply to Jim.UT, 01-15-2005 21:40:51 | | OK, john in la AND Jim.UT :) These are the diagrams I had in mind and suspected Dave sent him. If I hadn't a let my grumpy old f@rt take over I'd a probably sent the same things at the same time you did. PS. I just won the bid on some '57 Ford brochures which look like they show the red workmasters and look like they show the fenders very well. They say 600 and 801, but the couple pictures show the all red powermaster. That was only the 601's wasn't it? | | [Log in to Reply][No Email] | |
| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 12:40:59 | | Well, Dave's diagram did a good job of showing how an alternator needs to be connected to the electrical system, but it was not a picture of the original wiring. My wiring harness is in good shape, so I don't want to slice it open to follow wires. There is a red wire coming off one side of the 'generator light' which disapears into the harness. I need a diagram which shows where the other end of that wire is located. The commonly available 6 volt diagrams (with the ammeter) don't show that red wire anywhere because, if it's present, it isn't used. Anybody else? | | [Log in to Reply][No Email] | |
| montana charlie Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 12:40:59 | | Thank you for the quick response, Dave. I really do need the 6 volt, positive ground, wiring diagram for an 871 (Select-O-Speed) with the dash-mounted 'generator light' and no ammeter. The alternator was custom built for me because I wanted this tractor to start charging it's battery (again)...but did not want to modify the tractor to a point where it could not be easily returned to factory specs. Even though it was built especially for me, it is not an 'exotic' unit. It's a Delco 10-SI with a 6 volt, one wire (low RPM) regulator, and uses a positive ground rectifier. A guy could built it himself from any 10-SI core.
I just didn't want the extra hassle. Many guys (who don't like generators) decide to go for the 12 volt modification, just so they can have the advantages of an alternator charging system. It ain't necessary...unless they also want to use 12 volt accessories. If anybody is interested in 'my way' of changing over, I will gladly share the source of my alternator. I made my email address 'visible' so you can send what you have, Dave, and thank you. | | [Log in to Reply][No Email] | |
| Dave H (NY) Report to Moderator
| Re: Wiring diagram for an 871 with idiot light in reply to montana charlie, 01-15-2005 12:40:59 | | | Charlie, I have several wiring diagrams, but I don't believe you can use an alternator in a positve ground setup only a generator, and I am not sure about 6 volts from an alternator since I have never seen one at that voltage. My e-mail is childebrand@hvc.rr.com e-mail me and I will send you the diagram and just let meknow what you have and I will send you the proper diagram |
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