Corrosion on heater wire connection.

Hi folks.

My heater suddenly stopped working, and checking the cabling for continuity I noticed one of the heater wires not working. The crimp in the molex plug was a bit corroded (blue/brown discolouring), and there was also some corrosion on that header pin. I scraped off the corrosion and the heater worked for a little while, but then stopped again. The other pins also have some signs of wear.

Picture of connection panel pins:
Picture of heater plug:

I have the following setup:
* Tech zone remix.
* Fat wires to my stripboard connection panel at the x carriage hooked up with these molex connectors.
* Thinner (1/0.6mm) solid core wires from there to the heater block.
* Aluminium 10x10x30mm heater block running with two of these resistors in parallel, having a combined resistance of 3.6 ohm (thereof 0.2 ohm from the multimeter). The resistors are secured with quiksteel (which smells pretty bad).
* The thermistor is on a ring terminal, mounted between the heater block and the detachable nozzle, which is leaking PLA like there's no tomorrow, but I digress...

I have though up several explanations which might be - and probably are - totally wrong:
* Low quality connectors. Thus bad metal or not secure enough connection. - Not likely to happen already, as the machine haven't run that much.
* Too heavy gauge wire from the extruder board compared to the gauge of the connector pins. - I really don't know if this is a reasonable argument.
* The heater block running 3.6 ohm puts more electricity through, thus more stress on wires. - Or is my electric understanding totally wrong here?
* A short? - I can't find anything.
* Some chemical from the paint leaked on to the pins when I sprayed the header.
* Me forgetting to plug in the heater block to the panel, and then starting to heat up. - Happened right before it stopped working.

Possible solutions:
* Clean the pins properly.
* Accept it and crimp new plugs on now and then.
* Solder the pins directly. - But I really, really enjoy the ability to exchange heaters fast.
* Beefier connectors.
* Lower gauge wire from the extruder board.
* Rambling on the forum?

Anyway, have anyone else encountered this problem?

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-Nudel
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A 3.6R heater will draw 3.3A. Those look like 0.1" connectors to me, which I think will have a rating less than that. I have had similar problems with connectors that are well within their rating. I think constant vibration seems to increase the contact resistance. Either that or the ABS fumes corrode it!

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[www.hydraraptor.blogspot.com]

Thanks, yes my mendel vibrates a lot, especially with x axis motion since I don't have any thick sheet to stiffen the frame. Also these connectors do have a smaller contact area than I like.

Still, I ran the machine for a while with nichrome, and I do believe I would have noticed if anything started corroding then. The single core wire I use is rated at 1.8A only, so I'm probably pushing my luck with 3.3A. I'll crimp new wires and clean up or solder on new header pins, then build a heater block with a single resistor instead. If the problem persists I'll hook up the heater with a deans connector or something. And I'll be on the lookout for higher rated, sturdier connectors.

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-Nudel
Blog with RepRap Comic

You could try conductive grease to protect the connection. I learned a lot from the recent grease discussion, and dielectric grease might help.

Sounds like a good idea Buback, and yes, that was a good thread, thanks for bringing it up. I have some Valvoline Clean Tronic spray which claims to clean, preserve and lubricate electrical contacts. Since it's not a grease, I fear it runs too much to leave a long lasting protection on these small pins. Think it'll work? I'll test it, but have ordered some dielectric grease off ebay anyway.

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-Nudel
Blog with RepRap Comic