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I hope this finds all of you healthy and out of harms way.

I need some electrical help, please. I think I need a wiring harness, or guidance for making a harness, for my Rancilio L4. I refurbished the machine with new components and now I am melting terminal covers and have shorted two power switches. My guess is that wiring harness I built might be causing excessive heat at the main power switch. I suspect the resistance in my harness is causing the excessive heat. I used silicon covered wire and crimped butt splices that are not so pretty. That said, I am not sure what my problem really is. I think I am looking for a new harness, or recommendations on an adequate splicing technique. Can you help? Thank you.

It is difficult to tell from the pictures. Maybe a picture of the crimping tool, the connectors you're using and more information about the wire? What size wire would also be useful. And a picture of a crimped terminal so we can see the crimp.

Ira

It could have been that the switch already had a lot of carbon built up on the contacts and that it melted due to the heat generated there within.
But, along with replacing the switch, do replace the wires, you'll be able to tell how badly the wires overheated by how crispy the insulation got. Use a heavier, stranded (Not solid core) copper wire of at least the gauge you're replacing, but better to exceed itthermal conductance and use a 12 gauge, stranded copper high-temperature wire. The thermal conductivity of a bigger wire is just as important as the electrical conductivity. Take your time with the crimping, it can be done with linesman's or even needlenose pliers if you don't have a crimping tool, just make one fold at a time and be gentle.

Thank you for the replies. Both new switches were from espressoparts, rated 20A 125V and 16A 250V. The terminals also came from esspressoparts. I used iFlight 14awg silicone wire, 12-10 crimp/heat shrink butt splices, crimped with either a ratchet crimper or standard wire crimper. I pull-tested each splice and terminal with a fair amount of force to be sure they were held together. Only the main power switch overheated. There are no indicators of overheating anywhere else that I can see.

Is there a better way, or 3-way connector, to splice the wires?

Here is part of the original harness. It is much simpler with two wires into one terminal eliminating my need for butt splicing. I did not duplicate this because I could not find a terminal that would fit two 14awg wires.

You've done everything properly as far as I can tell from the pictures and the story. You have 14 gauge wires in a 10-12 splice, but that's acceptable as it is the only way to work with pigtailing the wires together.
I'm still fixating on the fact that both terminals on the same pole of that switch are so badly melted. I think I am leaning toward the belief that switch wasn't making good contact and burnt itself to a crisp.

Do you have a clamp-on ammeter to make sure that the machine isn't somehow drawing excessive current, I don't think it is because it would have to exceed 20A by a lot for a while to melt the switch that well, and exceeding 20A for a moment should pop your breaker... But just to rule it out.

I do not have a clamp on ammeter... yet. In the meantime, I plan to strip the burned wires back, put on new terminals and a new switch. I did this a couple months ago and it worked until now. While I hope for the best, I do not believe this will fix the problem. I changed my habits and routine so as not to leave the machine unattended when it is on.

I'm assuming you have the correct crimper for the open barrel terminals, otherwise it's essentially impossible to get a decent crimp.
The only other thing I'd say is, make sure the terminals fit very tightly so they make the best possible connection.

Ira

I am not sure I have the correct crimper, but I've botched enough terminals with a variety of tools trying to get a good crimp that I think I have a decent technique now. I am slow in the crimping department, but have gotten them to look decent and hold well. All of the fittings are clean and fit tightly. I just cut off about 2in of the power supply cord that was felt a bit less pliable than the rest of the wire. I am not sure if this was cause or effect. In any case, I installed a new switch and new terminals. A short test run proved well enough to call it a night and hope for some good strong Corona killing espresso come morning.

For those you want a crimper with jaws that look like this:



Without that it will be quite difficult to get a good crimp.

Ira