[AT] tractor electrical question--I think its fixed!!!

Sun Aug 29 04:29:24 PDT 2021

There's nothing like finding the excuse to install a 12' gantry crane!
That is going to be very handy in the future.

SO

On Sat, Aug 28, 2021 at 10:16 PM John Hall <jtchall at nc.rr.com> wrote:

> Well now that the 454 is done I started pulling the engine out of my
> combine today. This will be interesting. I had to put in a 12' high gantry
> crane for this project......
>
> John Hall
>
>
> On 8/28/2021 7:08 PM, Carl Szabelski wrote:
>
> Glad to here it’s resolved. Now I’ve got to find something else to work
> on. Maybe something on that two year old list my wife has, or maybe not.
> Too hot and muggy here in Michigan to do anything anyway. 90+ degrees with
> about 80%+ humidity. No relief until middle of next week, unless Ida pushes
> more warm and humid air North by then.
>
> Carl
>
> On Friday, August 27, 2021, John Hall <jtchall at nc.rr.com> wrote:
>
>> I THINK the problem is solved!!!
>>
>> First let me say thank you to all who offered ideas--all ideas are
>> appreciated when you have no idea where to turn next. If I try to reply to
>> everyone, gonna be a cluttered mess of emails. If I don't mention someone
>> who tossed out ideas or info, don't be offended.
>>
>> Special thanks to Carl for being so diligent researching this. It was
>> nice to bounce ideas off someone doing the same research!
>>
>> Long story short, this system uses a resistor wire. Given time, it would
>> get hot and fail. It is also noteworthy this is the HOTTEST tractor IH ever
>> built by design (routing of exhaust mainly) so that pushes the heat even
>> higher. So between this list, the Facebook IH Group, local starter shop, an
>> older car mechanic, internet old car forums/groups, a custom car wiring
>> harness builder and help from Ken Updike, I determined this system uses a
>> resistor wire, not a coil with built in resistor. Internet searches on
>> ignition systems give better explanation than me but I'll sum up how it
>> works. Resistor wire feeds aprox 6V to coil, but during cranking the
>> solenoid on the starter also actuates a bypass circuit to feed 12v for as
>> long as starter is engaged (hotter spark, starts easier, especially in cold
>> weather). The jumper wire proved something was going on once the system was
>> hot. In researching I found that resistor wires are part of the harness,
>> fail more often than you think, and the workaround is either buy a new
>> harness or put on one of those ceramic ignition resistors with a separate
>> feed from the key switch. These resistors were quite common on a lot of
>> older cars, I picked one up at Oreileys. A lot of the old car crowd has
>> posted doing this same thing. This setup still allows for the boost in
>> voltage during cranking, where replacing the coil with a 12 internal
>> resistor on its own wire would eliminate that feature.Note that all the
>> original wiring must be left intact and hooked up!! I found no one selling
>> resistor wire in quantities need for a repair such as this--probably part
>> of the reason is who would really know the specs on the wire to know what
>> to get. I did see mention of folks using a donor harness to salvage that
>> wire.
>>
>> One thing that confuses a lot of people (including me until 3-4 days
>> ago)--the voltage at the coil input WILL vary depending on if the points
>> are open or closed--Greg Easley pointed this out if anyone wants to study
>> further.
>>
>> Anyway, I ran the tractor for over an hour tonight mowing--I've ran out
>> of big stuff to cut so pushing hard trying to get the temp way up was
>> difficult, so I grabbed another gear and pushed pretty hard and got it as
>> warm as I could. Also I had all the sheet metal off so it was probably
>> running cooler as well. I'm pretty darn confident its now fixed, enough
>> that I'm gonna get the haybine hooked up and cut some hay soon (I hope).
>>
>> One of the late comers to comment on this was Ken in AZ. I must say he
>> nailed everything from what the wire is made of to how to work around the
>> problem.
>>
>> Spencer, thanks for keeping this list going, the gang really stepped up
>> on this one!!
>>
>> John Hall
>>
>>
>>
>>
>>
>>
>>
>> On 8/27/2021 4:52 PM, Carl Szabelski wrote:
>>
>> John,
>>
>> Found what I believe to be info on the starter relay and it appears there
>> is no internal resistance, so back to square one (?). You indicated that
>> with the wire removed from the R terminal you have 12V at the terminal.  If
>> putting the wire back results in 6V at the coil, then that wire has to be
>> what is causing the drop. There is a splice in the harness that splits the
>> 12V in the harness. The part of the wire going to the coil may be high
>> resistance wire. Have you tried bypassing that portion of the harness by
>> running a wire from the R terminal to the coil with the original wire
>> disconnected?
>>
>> Running out of ideas.
>>
>> Carl
>>
>> On Friday, August 27, 2021, Carl Szabelski <c.s.szabelski at gmail.com>
>> wrote:
>>
>>> John, I’ve gone trough the wiring diagram and traced all the feeds from
>>> the R terminal on the starter relay, one of course goes to the coil. All
>>> the other feeds go to things like sensors, the fuel shutoff valve, etc.
>>> They all form parallel circuits to the coil, eventually going to ground. If
>>> there was a short anywhere it would take the R terminal to ground and you
>>> wouldn’t see any voltage at the coil, or possibly anywhere else.
>>>
>>> I’m still of the mind that your issue is with the starter relay. I don’t
>>> know the internals of the relay, but from how I believe it should work is
>>> that the relay has an internal resistance built into it to drop the voltage
>>> to 6V after the start. During a start the resistance is bypassed and you
>>> get 12V at the coil, necessary for cold weather starts. This is all done
>>> with two sets of contacts built into the relay. What I think is happening
>>> is the contacts for the internal resistance are remaining closed after the
>>> start, thereby leaving that resistance in the circuit. That along with any
>>> internal resistor in the coil is too much resistance at 6V for the coil to
>>> work properly. The contacts are probably shut closed after years of arcing.
>>>
>>> One thing to try is hitting the relay to see if you can break the
>>> contacts free, assuming they are there. Also as I mentioned earlier, see if
>>> you can open up the relay and look inside.
>>>
>>> Carl
>>>
>>>
>>>
>>
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