The recipes for the IC2 items are missing when using https://minecraft.curseforge.com/projects/ic2-classic, because it does not contain a coil. I suggest replacing the coil with an electronic circuit in this case.

IC2 classic uses the same mod id as the original IC2, so I cant easily check for the mod id (which I currently do). Mods shouldnt reuse a ModID of another mod just because its a "classic" version of it as it breaks expectations, but thats just my opinion.

I will probably end up replacing the coil with the circuit like you said, even though I dont like fixing issues other mods cause.

I've now opted for Tech Reborn for my modpack. Objectively a won't fix seems appropriate here. Thank you!

as this is only a recipe issue, it could be changed by any of the recipe changing options out there (like crafttweaker). I will change it, as this is a rather simple change - but its rather low priority for me at the moment.

I've decided against doing this change in 1.12 since it would cause issues with autocrafting systems in existing worlds and there is no easy way to detect if the installed ic2 version is the original or classic variant.
I will make this change with 1.13.
In the meantime i recommend using crafting recipe mods like crafttweaker to change this manually.

Hello,

Here is CraftTweaker code to add recipes for IC2 Classic for anyone who wants it:

recipes.addShaped(<energyconverters:energy_consumer_eu:0>,
[[<ore:stone>, <ic2:itemcable:1>, <ore:stone>],
[<ic2:blockelectric:8>, <ic2:blockmachinelv>, <ore:ingotGold>],
[<ore:stone>, <ic2:itemmisc:451>, <ore:stone>]]);

recipes.addShaped(<energyconverters:energy_consumer_eu:1>,
[[<ore:stone>, <ic2:itemcable:4>, <ore:stone>],
[<ic2:blockelectric:9>, <ic2:blockmachinelv>, <ore:ingotGold>],
[<ore:stone>, <ic2:itemmisc:451>, <ore:stone>]]);

recipes.addShaped(<energyconverters:energy_consumer_eu:2>,
[[<ore:stone>, <ic2:itemcable:8>, <ore:stone>],
[<ic2:blockelectric:10>, <ic2:blockmachinelv>, <ore:ingotGold>],
[<ore:stone>, <ic2:itemmisc:452>, <ore:stone>]]);

recipes.addShaped(<energyconverters:energy_consumer_eu:3>,
[[<ore:stone>, <ic2:itemcable:9>, <ore:stone>],
[<ic2:blockelectric:11>, <ic2:blockmachinelv>, <ore:ingotGold>],
[<ore:stone>, <ic2:itemmisc:452>, <ore:stone>]]);

Simply paste the code into a file named whatever.zs and place it in your .minecraft/scripts folder.
ex. ( %appdata%\.minecraft\scripts\energy_converters.zs )
Requires the following to work:
-CraftTweaker
-IC2 Classic
-Energy Converters
-Forge
-Minecraft

<3

Note: This will not work with CraftTweaker above Minecraft 1.12.2 as the syntax has changed.