[AT] tractor electrical question
John Hall
jtchall at nc.rr.com
Thu Aug 26 19:16:26 PDT 2021
Yes, overload. If the voltage fluctuates everytime points open and
close, wouldn't it be impossible to get a meter reading with engine running?
Coil mounts to head. I had to use the same bracket to mount the new coil
(new bracket won't line up). I question do the coils really need
grounding? I mean they are completely covered in paint, never seen
anyone scuff all the paint off to make a good connection. Heck I'd be
willing to solder a ground wire to the case at this point. I did check
and the case on the coil did appear grounded by the meter
Ohmed old and new coil, both read about the same--across the 2 terminals
and from pos to output for cap wire.
For giggles, I can try a couple other machines with similar style coils
to see if I can get a read on them that is consitent and not overloaded
with engine running.
To further run some checks I unhooked the wire from the R terminal of
the starter solenoid. When I spun the engine over it shot up to around
11V before the tractor cranked--I would assume it make it to12 if I
would have yanked the coil wire. That wire is actually 2 wires--one to
the coil, the other is a supply--the supply was reading 5-6 ish prior to
cranking. I have yet to find a stand alone resistor, so I am thinking
there is one in the harness or a resistor wire?
It seems to me the system functions fine cold--supplies 6V to coil and
jumps to 12 with starter engaged. So wondering is the problem on the
distributor side. I picked up a new condenser today and swapped it out.
If no moments of revelation occur before tomorrow afternoon, I'll go mow
some more and see if condenser swap worked. If not, I'll be armed with
jumper wire and multi-meter.
John
On 8/26/2021 9:09 PM, Howard Pletcher wrote:
> OL? You are using a digital voltmeter for this, right? I think it is
> saying you are OverLoading the 20V or whatever scale you have it set on.
>
> Have you tried getting a reading when you first start it before it
> runs rough? You may still get an OL or perhaps not. This suggests to
> me you do not have a good connection from the block to the coil case
> which is how the high voltage circuit should be completed and you are
> getting voltage spikes finding their way back to the coil through
> other circuits and causing extra heating in the coil. Both of your
> coils may not be bad as suspected. Check and clean the mounting of
> the coil bracket to the engine and the contact of the bracket to the
> coil. It's not something I'd think of when doing maintenance, but now
> it seems like a possibility.
>
> On Thu, Aug 26, 2021 at 8:08 PM John Hall <jtchall at nc.rr.com
> <mailto:jtchall at nc.rr.com>> wrote:
>
> points, plugs, cap, rotor and coil are all new. I verified with my
> 50 year old parts book and it has the same part# for coil as what
> online parts at Case is showing. The new coil has 12V on the
> outside, but the bill had 6V. Box was sealed up, but it came from
> overseas, so a lot of variables there
>
> Point gap was verified when I had the distributor off and plate
> out so I could make sure weights were free and springs not broken.
>
> I had my voltage regulator with me yesterday. When I tried to
> check at coil with engine running rough, it showed OL for whatever
> reason. I've checked so much stuff lately that I'm not sure but I
> think I got 6 and 12 volt readings depending on where the points
> were once I shut the engine off. I tried checking the voltage with
> engine running at the fuel solenoid for reference and it was
> floating all over the place from 4 to 13.5V. This was observed
> with the engine hot and running rough. With engine not running it
> holds steady a little over 12.
>
> Last night I also found that the wire to the coil and the wire to
> the R terminal on starter solenoid can read 6V (little less
> actually) while the wire going to the fuel solenoid in the carb
> was reading 12V.
>
> John Hall
>
>
>
> On 8/26/2021 6:35 PM, Howard Pletcher wrote:
>> It's not unheard of, particularly since many of those parts now
>> come from overseas. To me, swapping with another if you can find
>> something to swap with would be the easiest way to prove or
>> eliminate that as a possibility.
>>
>> Make sure your points setting is close to spec and they are clean
>> as that would affect the ignition. Have you looked at your
>> plugs, not thinking that's the problem, but if they are fouled or
>> badly gapped, they could have an effect. You also might run it
>> until it heats up and needs the 12V to see if it still shows 6V
>> to the coil. If not, then it's somewhere else in the circuit.
>>
>> Many of the other things suggested have no connection with the
>> ignition circuit.
>>
>> On Thu, Aug 26, 2021 at 5:12 PM John Hall <jtchall at nc.rr.com
>> <mailto:jtchall at nc.rr.com>> wrote:
>>
>> Howard, you are leaning toward new coil and old coil are both
>> bad?
>>
>> John Hall
>>
>> On 8/26/2021 3:47 PM, Howard Pletcher wrote:
>>> No, what he is reporting is just what should be happening.
>>> With the points open, no current is flowing through the
>>> primary circuit and there is 12V at the + side of the coil.
>>> When he bumped the starter and closed the points, the
>>> current flowing through the resistor in the primary circuit
>>> results in a voltage drop so that there is now 6V on the
>>> coil as intended.
>>>
>>> The wire from the starter to the coil does send 12V directly
>>> to the coil, but this is only engaged while the starter is
>>> cranking in order to produce a hotter spark for starting and
>>> is not connected to 12V the rest of the time.
>>>
>>> The fact the coil seems to require 12V to its terminal when
>>> hot points to an internal problem in the coil as discussed
>>> by Dell in the Yesterday's Tractors article.
>>>
>>> Howard
>>>
>>>
>>>
>>> On Thu, Aug 26, 2021 at 2:53 PM Carl Szabelski
>>> <c.s.szabelski at gmail.com <mailto:c.s.szabelski at gmail.com>>
>>> wrote:
>>>
>>> By the way, I believe it’s not the coil and is related
>>> to the cranking motor. Especially since the voltage
>>> drops when you bump it like you said. Something in the
>>> motor may be partially shorted or corroded, causing a
>>> voltage drop to the coil. The coil should always see 12V
>>> whether or not there is a resistor, internal or
>>> external. The resistor is essentially after the coil
>>> winding and drops the voltage after the winding, not
>>> before it. If the engine is running fine when you
>>> directly connect 12V to the coil, the coil is working
>>> like it should and is good.
>>>
>>> Carl
>>>
>>>
>>>
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>> --
>> Howard
>>
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