Dodgy switches

[Old Koreelah]

Just learned something while installing some wig-wags on my plane ready for Parkes AirVenture. My previously-installed landing lights and strobes were no longer working.

 

After lots of grovelling around in my shipping container (where my baby spends much of her time) I tracked the fault in both cases to the switches.

 

I presumed they were good quality and had installed them about a decade ago. 

 

 

[Thruster88]

Have experienced this also, the toggle flips over but nothing happens inside the switch. Obvious when it's the master or ignition switch on the Thruster.

 

 

[IBob]

Puts me in mind of some WW2 aircraft they pulled out of an English bog some years back: supposedly all the Honeywell switches were still in good working order...

 

 

[Downunder]

I was given a tip once, with toggle switches. 

 

Use 240 volt rated switches in 12 volt applications.

 

They will last longer and are not much more expensive.

 

 

[facthunter]

  Bit of corrosion or a weak spring finishes them off. You could make basic push pull types  (bombproof design) your self. Guarded ones are probably better quality.  Solenoids have always been unreliable. Nearly killed me several times (Sticking ON.) Nev

 

 

[Old Koreelah]

The lugs on newer (240v) ones I've installed are too small for the crimp-on connectors I have, so I've had to solder the wires on. I hope the heat from my soldering iron hasn't damaged these switches.

 

 

[Yenn]

You will be switching worse loads on 12V than 240V. It is not safer to use 240V designed awitches.

 

I have noticed in the last few years that the quality of switches in all sorts of equipment is getting poorer.

 

Buy a new piece of equipment and I bet that when it fails, it will be a switch problem. Drills and circular saws used to burn out armatures, now it is switches failing.

 

 

[facthunter]

 Yes . The 240 volt switches may not have the amperage capacity. I think the usual ones are 15 amp.  That's only about 180 watts with 12 volt. Nev

 

 

[Old Koreelah]

Good point, Yenn. I tend to leave my strobe switch on to reduce wear and the likelihood of failure, but it's not nice to people nearby while warming up. At least they get another form of warning before I start the engine.

 

 

[spacesailor]

Electrical Switches !.

 

The NONE maintenance product.

 

Has anyone tried a little lubricant  yet. I had good result from "Lanin" & Inox. aboard my yacht, to combat damp switchgear failure.

 

spacesailor

 

 

[KRviator]

The problem with switching a 12VDC load with a 240VAC switch is the arc damage. 

 

240VAC passes through 0 Volts 50 times a second, rendering any arc minuscule, whereas using such a switch to control a DC load will have the switch taking the full circuit current (or higher if you're switching a motor) instantly, or breaking the circuit under load.

 

Unless a switch has a DC rating, it's not at all good practice, yet alone a good idea, to use a 240VAC switch for any meaningful DC load.

 

 

[facthunter]

Having your strobe light on on the apron is considered poor form. (or worse). Put it on when you approach the runway and ready to go.  The rotating red light means you are about to start engines or have (at least) one running. . Nev

 

 

[onetrack]

There are switch mechanisms and there are switch mechanisms. The design of many switches is just simply deficient, in their construction, and in their operating principles.

 

Too many switches are too complex in their construction, with too many moving parts. Others are built with inadequate strength in the switching components.

 

Too many have inadequate mechanism sealing against dust and moisture.

 

I prefer simple push-pull, or good quality well-sealed toggle switches. Rocker switches are generally nothing but trouble.

 

Horizontal Rocker switches are the worst - dust and general debris falls straight into them, and can't be got out without regular vacuuming.

 

I've got a 230mm Hitachi angle grinder that has a particularly bad design, on-off switch. It's poorly designed and made of weak components, and it fails regularly.

 

But the worst part is, when it fails, it stays on!

 

There's nothing worse than wielding a bloody heavy, 230mm angle grinder with a powerful motor, and lots of centrifugal force thrusting it out of your grip - without it not shutting down when you expect it to!!

 

 

[facthunter]

 You will pay a lot of money for a good switch. Blade rotating with a  clamp effect seems the design used for multi phase start with load situations. I don't believe relay necessarily makes things safer . It just cuts down the amount of heavy wire you need to use but it's something else to fail. Nev.

 

 

[skippydiesel]

The problem with switching a 12VDC load with a 240VAC switch is the arc damage. 

 

240VAC passes through 0 Volts 50 times a second, rendering any arc minuscule, whereas using such a switch to control a DC load will have the switch taking the full circuit current (or higher if you're switching a motor) instantly, or breaking the circuit under load.

 

Unless a switch has a DC rating, it's not at all good practice, yet alone a good idea, to use a 240VAC switch for any meaningful DC load.

 

Cant argue with your theoretical knowledge however most if not all of my (toggle) switches are rated to 240 V and so far - 10-20 years (not all installed at the same time) they are okay. I would also point out cost is a factor here - my supplier JayCar AeroSpace gives me a relatively cheap switch  that can be replaced at an equally cheap price. None of my JayCar switches operate vital functions ie the engine will keep turning even if all other systems pack it in.