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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal>Spencer, your comment about “the bracket is usually hiding whatever information is printed on it” sent me out to the barn with a flashlight and some tools, and of course you were dead-on correct. All looks good on the no-resistance-wire needed front. :)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Earlier today I put a new wire in place to replace the one the mice had chewed up, and I left in place the wire from the starter solenoid, so am happy to call that little project completed. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Dean VP, good thought about tracking information via the part number for the resistance wire, but there isn’t one—per the service manual diagrams it was originally just part of the wiring harness assembly, not a separate item that could be ordered or installed on its own. While attaching the new wire to the coil I noticed the stub ends of both the original wires that fed the coil, cut off right where they left the harness, and both replaced at some point by individual wires.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Dean Vinson<o:p></o:p></p><p class=MsoNormal>Saint Paris, Ohio<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><img width=1200 height=1600 style='width:12.5in;height:16.6666in' id="Picture_x0020_2" src="cid:image002.jpg@01DAFBEC.EF373FC0"><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> AT <at-bounces@lists.antique-tractor.com> <b>On Behalf Of </b>Spencer Yost<br><b>Sent:</b> Saturday, August 31, 2024 6:47 PM<br><b>To:</b> Antique Tractor Email Discussion Group <at@lists.antique-tractor.com><br><b>Subject:</b> Re: [AT] 3020 electrical, continued... "resistance wire"?<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>+1 on the resistance info on the coil. I have seen coils that say something like “internal resistor”, or “use without external resistor”. Don’t know if that’s universal. Also see “12V” or “6V” but again, don’t know if that’s universal.<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>What is nearly universal is the bracket is usually hiding whatever information is printed on it. You may want to slip it out of its bracket to see if you see any info on it.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Spencer<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'><img width=480 height=640 style='width:5.0in;height:6.6666in' id="Picture_x0020_1" src="cid:image001.jpg@01DAFBEA.8CFF1FA0"><o:p></o:p></p><div><p class=MsoNormal>Sent from my iPhone<o:p></o:p></p></div><div><p class=MsoNormal><br><br><o:p></o:p></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal style='margin-bottom:12.0pt'>On Aug 31, 2024, at 1:12 PM, Stuart Harner <<a href="mailto:stuart@harnerfarm.net">stuart@harnerfarm.net</a>> wrote:<o:p></o:p></p></blockquote></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal> <o:p></o:p></p><p>Hi Dean,<o:p></o:p></p><p>Working from your last question first. Do you need the wire from the solenoid to the coil?<o:p></o:p></p><p>That would depend on your ignition switch. IF the run wire is hot while in the START position, then no you don't need the secondary wire. Most ignition switches do not power the RUN wire while in the START position. There are several reasons for this with the most important being to reduce any extra load on the battery during start and to prevent reverse spikes from the starter back into any of the other electrical system. <o:p></o:p></p><p>This is easy enough to test. Remove both wires from the coil + terminal and put a test light on the one from the switch. Turn key to RUN, light should come on. Turn key to START, light should go out. If it stays on, you don't need the wire from the solenoid. My bet is it will go out, and you need the wire from the solenoid.<o:p></o:p></p><p>Next up was the do I need a resistance with the 12V coil? The short answer is maybe. I am a little surprised that the factory used a "resistance wire" on the 6V setup, but again, that was to protect the points primarily and the coil from overheating. Resistance wire is an older way of dealing with the points than a resistance block. The problem with resistance wire is it comes in many different amounts of ohms of resistance per length of wire. So you need to know the total amount of resistance required, then cut the appropriate length of wire to get that amount. Wire diameter also plays a part depending on how much current that wire was expected to carry. I think the use of resistance wire was eventually replaced by resistor blocks.<o:p></o:p></p><p>Now we get into the question of 12V coils and this is where I get a little bit fuzzy both from lack of total knowledge of the subject and fading memory from when I was a parts guy in the 1980's. IF I remember correctly, Ford and GM used a different coil that did not require an external resistor. Did it have an internal one? I don't know but I do remember looking up coils for vehicles and there would be different part number for "with resistor" and "without resistor". This may have been as Chrysler was changing to a system that did not require a resistor. Another fuzzy memory is some coils were grounded through the mounting strap and only had one + terminal, some had a + and - terminal and were not grounded through the body. <o:p></o:p></p><p>There may be writing on the coil that says if it needs a resistor or not. Or if there is a brand name and part number, it could be researched that way.<o:p></o:p></p><p>In any case, since it has been working fine with no burned points issues, my instinct would be to leave it alone and just replace the damaged wire. If it ain't broke, don't fix it. :)<o:p></o:p></p><p>All coils cause a reverse spike on the primary winding as the magnetic field of the secondary winding collapses. This is why points can arc and why there is a condenser connected to the points. A coil designed for 6V will work at 12 and will produce a hotter spark. The stress on the coil and condenser as well as the heat buildup in the coil will eventually damage it. If one is converting a 6V system to 12V everything will work fine as long as the coil and condenser are upgraded to 12V versions OR some provision is made to reduce the voltage to the old coil. IF the 6V system also used a reducing resistance it makes things more complicated and switching everything to 12V is just easier all the way around.<o:p></o:p></p><p>If you are curious, just do the test light procedure and you will find out how it is set up now. The big question will be how to keep the darned mice from doing it again! <o:p></o:p></p><p>Stuart<o:p></o:p></p><div><p class=MsoNormal>On 8/31/24 10:59, Dean Vinson wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal>Stuart and Dean, thanks for the quick responses. I’ll go ahead and put a new length of wire in there to replace the one that had some of the insulation chewed off, on the theory that whoever installed the old one knew what they were doing and in light of the fact that it’s evidently been installed for a long time and the tractor runs fine. But I still don’t really have a good understanding of the whole system as currently configured… my technical foundation is a little weak for stuff like this.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Stuart, you wrote “The purpose was not to protect the coil but to protect the points”, and Dean, you wrote “Starts on 12v runs on 6.” Ah, okay—so that’s why there are two wires feeding the coil? One from the starter solenoid to briefly provide 12V to the coil to generate an especially hot spark for starting, and then after the solenoid disengages the separate “resistance” wire from the ignition switch provides reduced voltage to avoid burning out the points while the engine is running normally?<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>I’m familiar with the resistors in the little ceramic blocks, since my Super M has one, but it’s an after-market add-on since that tractor left the factory with a 6V battery and was at some point converted to 12V. Following the same logic, it’d make sense to me if the 3020 had a physical resistor in front of the coil, since they were designed from the get-go for 12V batteries but still used 6V coils. But the service manual wiring diagrams don’t show any resistor, just a “resistance wire,” and this little four-foot section of #14 stranded wire doesn’t provide any resistance to speak of.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Oh, wait… okay, maybe that makes sense after all, because I think this four-foot wire is not OEM and I think the coil on the tractor is not the OEM 6V coil but is rather a 12V replacement. A 12V coil wouldn’t need a resistor to avoid burning the points, correct? So 12V to the coil is okay all the time and I don’t *<b>need</b>* a resistor, but I need that 12V to come from the ignition circuit since the 12V from the starter solenoid is only there when starting. Sound right? And if so, do I strictly need the wire from the solenoid? (Not that I’m intending to remove it… just trying to think through how the system works as currently configured).<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Thanks very much,<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Dean Vinson<o:p></o:p></p><p class=MsoNormal>Saint Paris, Ohio<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> AT <a href="mailto:at-bounces@lists.antique-tractor.com"><at-bounces@lists.antique-tractor.com></a> <b>On Behalf Of </b>Stuart Harner<br><b>Sent:</b> Saturday, August 31, 2024 9:31 AM<br><b>To:</b> <a href="mailto:at@lists.antique-tractor.com">at@lists.antique-tractor.com</a><br><b>Subject:</b> Re: [AT] 3020 electrical, continued... "resistance wire"?<o:p></o:p></p></div></div><p class=MsoNormal> <o:p></o:p></p><p>The only experience I have with coil resistors was on older Chrysler products that used a block type resistor usually mounted near the coil. The purpose was not to protect the coil but to protect the points. Running 12V through the points would cause them to burn quicker than running only 6V.<o:p></o:p></p><p>The resistor was wired in such a way that when starting there was 12V to the coil as it was tapped off of the solenoid wire, but when you put the key back to run, the coil was powered through the ignition switch, through the resistor and was only getting about 6V.<o:p></o:p></p><p>The resistors were potted in a ceramic block and mounted in the open as they would generate heat from dissipating that excess 6 volts. If the resistor failed the engine would start but die as soon as you dropped the key back to run. It was fairly common, easy to diagnose and easy to fix by replacing the resistor. Like any light bulb, they just burned out at random times.<o:p></o:p></p><p>It sounds like your 3020 is kind of wired that way. If you are seeing no resistance on the wire, it may have been replaced in the past or the resistor has been removed. It will run, but will be hard on the points. If it was a resistance wire it would have been left out of the harness to dissipate the heat.<o:p></o:p></p><p>Hope this helps,<o:p></o:p></p><p>Stuart<o:p></o:p></p><div><p class=MsoNormal>On 8/31/24 00:11, Dean Vinson wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal>Tinkering with the 3020 yesterday and I opened up the dashboard panel to see what was behind it, and found a rosy colored mousenest decorated with the insulation from a formerly-red wire stringing back through there. There’s a three-inch section of wire where the copper strands are exposed, oxidized dark but still intact with good continuity. <o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>I can replace the wire easily enough, but I’m trying to get my head around its function. Near as I can tell from the wiring diagram it’s a “resistance wire”. It’s one of two wires connected to the input side of the coil, the other one coming from the starter solenoid. Service manual wiring diagram shows it coming from the ignition switch, but this one comes from a circuit breaker mounted below the ignition switch. It’s outside the harness so presumably a replacement for an original wire that failed at some point.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>The battery is a 12-volt and the parts manual says the coil is a 6-volt. Resistance across the coil tests at 2.8 ohms, and 12V applied at the input side tests at 12V at the output side, both of which suggest this coil is a 12-volt rather than 6 (according to some websites I found with tips on how to tell the difference).<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>So if the “resistance wire” was intended to protect the 6-volt ignition system from the 12-volt battery, but the OEM coil was replaced with a 12-volt, do I need to replace the wire or can I just remove it and call it good?<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Dean Vinson<o:p></o:p></p><p class=MsoNormal>Saint Paris, Ohio<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><div><p class=MsoNormal><image001.jpg><o:p></o:p></p></div><p class=MsoNormal><br><br><br><o:p></o:p></p><pre>_______________________________________________<o:p></o:p></pre><pre>AT mailing list<o:p></o:p></pre><pre><a href="mailto:AT@lists.antique-tractor.com">AT@lists.antique-tractor.com</a><o:p></o:p></pre><pre><a href="http://lists.antique-tractor.com/listinfo.cgi/at-antique-tractor.com">http://lists.antique-tractor.com/listinfo.cgi/at-antique-tractor.com</a><o:p></o:p></pre></blockquote><p class=MsoNormal><br><br><o:p></o:p></p><pre>_______________________________________________<o:p></o:p></pre><pre>AT mailing list<o:p></o:p></pre><pre><a href="mailto:AT@lists.antique-tractor.com">AT@lists.antique-tractor.com</a><o:p></o:p></pre><pre><a href="http://lists.antique-tractor.com/listinfo.cgi/at-antique-tractor.com">http://lists.antique-tractor.com/listinfo.cgi/at-antique-tractor.com</a><o:p></o:p></pre></blockquote><p class=MsoNormal>_______________________________________________<br>AT mailing list<br><a href="mailto:AT@lists.antique-tractor.com">AT@lists.antique-tractor.com</a><br><a href="http://lists.antique-tractor.com/listinfo.cgi/at-antique-tractor.com">http://lists.antique-tractor.com/listinfo.cgi/at-antique-tractor.com</a><o:p></o:p></p></div></blockquote></div></div></body></html>