Electrical Schematics

[markejackson02]

When reading the electrical schematic, each line is annotated with something like 21WE17B20.  I assume this is to help identify the line at the source and destination.  Do the numbers have any other significance like wire gauge or voltage or anything?

PS.  Are the fuses indicated anywhere on the schematic?  Not a lot of experience reading these things.

[milotron]

Yes, all of the above.  If you have the service manual at the front of the electrical section is a legend to what all of the letter mean.

For example:

21 = aircraft type/12V

WE = warning system; gear position

The last five alphanumeric are identifiers for the conductor and tend to be in an increasing sequence from the source, increasing at each connection or connector, although not totally consistent.

 

Fuses are shown, as are circuit breakers.  Circuit breakers look like a big 'C' with a 5A ( 5 amps ) beside it for example. Fuses look like big 'S' with similar ampacity notation. All of them all note function in the wiring diagram, but they only show factory wiring, not much for avionics.

 

iain

[Yetti]

And they are actually written on the wire in the plane in several places

[markejackson02]

You guys are the best.  I found the fuses for the panel lights on the schematic.  

I'm a little puzzled.  There are two 5A fuses under the glareshield wired in parallel to the transistor in the panel dimming circuit.  One of them is broken.  I ordered a replacement.  The lights still work with just the one fuse.  Why do they have two fuses in parallel?  Is it to even out the load or something?  They appear to be sourcing the power from the same place and delivering it to the same place.

 

[markejackson02]

Never mind.  It looks like the broker fuse goes to the radio package plug.  It used to power radio lights which are now internal to the units.