[AT] 3020 electrical, continued... "resistance wire"?

[Stuart Harner]

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.

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.

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.

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.

Hope this helps,

Stuart

On 8/31/24 00:11, Dean Vinson wrote:
>
> 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.
>
> 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.
>
> 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).
>
> 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?
>
> Dean Vinson
>
> Saint Paris, Ohio
>
>
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