Anatomy of an Air Ministry Ignition Switch
 

I have two types of Air Ministry toggle switches, one a simple two wire on/off toggle, "5c/622", and a 4 wire toggle, "5c769", which is two position: A to B, or A to C and D.

The round porcelain base is 2.25" in diameter, with the porcelain height on "622" being 5/8", and the height of "769" being 1/2". They both have two mounting holes 1 5/8" apart

The brass cap screws off from the top. THIS IS THE PREFERRED WAY OF ACCESSING THE SWITCH TERMINALS, which hold the wires by brass setscrews. The internal assembly is held to the porcelin by two brass screws on the bottom, but is is a poop to reassemble, especially "622", so just access from the top.

These were sourced from Retrotech.

Hope this is interesting for some.

Russ,
I wonder what the difference is between 5C/622 & 5C/623? I'll have a 623 switch in a few days and will post some pictures of it...

Are there any markings for specifications... such as 250v 5amp?

rob

Rob -

No rating markings, but as you can see they have very husky blade connectors.

While I didn't specifically mention it, you can see the set screws for the wires in the photo as well as the inside mounting holes.

best,
russ

I belive the 5c/623 is a three position switch i have several i will dig one out and take some pictures.

Russ,
If I interpret the photos correctly, the 5c/622 is clearly marked and on the left in the first 2 pics, but I believe is the right one in the third picture. If that is correct, it is a normally closed (connects when in the down position), which would be consistent with a magneto switch. They connect the mag to ground when turned off. The other appears to be a DPST (double pole, single throw) switch, i.e. to activate two circuits at the same time.
Did Retrotech indicate what each was for on your project?

i lifted this straight from another forum with essentially the same question.

5C/662 - Tumbler switch, single pole, 5 amps 1 way
5C/623 - As above, 2 way with 'off' position
5C/769 - As above, 2 way without 'off position
5D/551 - As above, double pole, 5 amps Type A, 2 1/4" diameter

I will post some pics as soon as i get a chance

Yep, I started that thread too! My next question on that thread was "so what does this all mean?"

Do we have an electrician in the audience? I just want to make sure that I understand what it is that they told us.

(by the way, that other forum isn't half bad: Historic Aviation - Key Publishing Ltd Aviation Forums)

Rob

For RobW,
I am reaching back into my old electronics traing for these, but I think I have it right based on the description (would need to see the circuit diagram of the switch to know for sure):
The 5C/662 is a basic on/off switch, SPST (i.e. one movement, one circuit). Were the switch turned over, into what we normally expect of a switch, it would be turning something on, like a light. When used for a magneto, it is mounted "inverted". The switch in the up position disconnects the one wire from the other, when down, the two are connected. In this case, though, for a magneto, connecting the two grounds the magneto coil, turning it "Off". Since there is no power going through it, it does not cause a short in the sytem, just in the magneto.
The 5C/663 - is either a pair of circuits controlled by a single lever, where there are 3 positions (Down - circuit "1" on, center both off, Up circuit "2" on" or DPDT), or a paired set of switch circuits operated by a single lever with similar switching. Can be used to reverse current and therefore reverse the direction of a D/C motor, or to alternate between two circuits that you do not want to work at the same time.
The 5C/769 pictured is a dual circuit switch (DP-), with one "On" and one "Off" ("on" - up, "Off" - down), (-ST), or DPST. That is essentially for two circuits that you want to work at the same time.
Hope that helps,
Glenn

now the real question is... is there any difference between a 5C/622 switch and a regular British house light switch (besides the cool Air Ministry crown stamp).

I would like to compare the two...

Rob

Dolly switches
 

Although a little late for me, based on the post above I have found a suitable and much cheaper replica - they are called "Dolly Switches" in England - see:

10 Amp 2 Way Brass Porcelain Dolly Light Switch

-- should work great.

You're welcome, everyone... :)