Because of the simplicity of the ignition system, there really is no diagram necessary. Husqvarna uses a simple two-wire harness in that unit (e.g.,
p/n 544 08 28-01) that has two female quick-connects at one end and one female quick-connect and a ring terminal at the other end.
The end with the ring connector is the magneto end. The female quick-connect there attaches to the magneto primary circuit control terminal, and the ring terminal there is secured under the head of one of the two magneto armature mounting screws.
The opposite end of the harness goes to the ON/OFF switch on the case side near the handle. This switch is a simple single-pole/single-throw switch that allows the engine to run when in its open position, and kills the engine when in its closed position. The engine shut-down occurs through the effective action of grounding the magneto control terminal to the magneto armature frame, as accomplished through the circuit through the ON/OFF switch when that switch is closed.
To identify the armature, harness and switch for your saw, go to the Husqvarna Manuals Download Page
for your saw, identify the list by the build date of your saw, and download the desired list. (I like the 2009-02 version as it has the sections identified and bookmarked, but be sure you ID the correct parts for your
saw. It might help to DL your manual as well as the 2009-02 version for reference purposes.)
The armature and harness will be found on the Ignition / Flywheel
page (items 7 & 8, respectively), and the switch will be found on the Air Filter / Intake / Carb
and Air Purge / On-Off Switch
pages, as item 9 (e.g.,
p/n 504 00 34-01, includes retainer bail).
If you are getting no spark from the plug wire when cranking the engine with the ON/OFF switch in its ON position, the problem must be in one of three places -- the magneto or its mounting, the harness, or the switch. A short between the magneto control terminal and the magneto armature will kill the spark, as will any short between the two wires in the harness. Similarly, an ON/OFF switch that fails to open (internally) will have the same effect as leaving the switch set to its OFF position.
If the engine will not stop when the ON/OFF switch is moved to its OFF position, an open magneto circuit is indicated. This can be due to a broken wire in the harness, a loose or corroded connection of the grounding (control) wire to the armature frame, a break in the magneto primary circuit to the control terminal, a loose or disconnected wire at the ON/OFF switch, or an ON/OFF switch that fails to close (internally).
While broken or shorted harness wires are easily repaired without replacement, any magneto or switch failures will usually require replacement of the failed component.