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

Sat Aug 28 19:15:54 PDT 2021

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 
> <mailto: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 <mailto: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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