Greetings: I've never been involved with a riding lawn mower but have been involved in electronics for 50 years. A friend asked for help with his Murray 12.5HP lawn mower that "suddenly stopped when the muffler shield fell off and he ran over it." As close as I can determine, the model number is ELT125380. I need a wiring diagram or explanation on how (and what) the power gets to the starter solenoid. When I turn the key there is no 12VDC at the hot terminal of the start solenoid. I'd rather not get involved with dismantling this mower to see where the wires go. Can someone explain what interlock switches are on this mower and how they are connected to make the solenoid circuit?

Karl

Keyswitch: A keyswitch has 3 basic wires.
1) battery (always "on")
2)ignition ( on when in the ignition position and at start position)
3) Starter ( on only when in start position)

Starter wire from keyswitch goes directly to solenoid.

Ignition switch goes to coil "hot"


That's a basic ignition system.

Keyswitch: A keyswitch has 3 basic wires.
1) battery (always "on")
2)ignition ( on when in the ignition position and at start position)
3) Starter ( on only when in start position)

Starter wire from keyswitch goes directly to solenoid.

Ignition switch goes to coil "hot"


Thats a basic ignition system.


OK... but there are at least two (according to the owner's manual that I found online... one under the seat and one connected to the brake/clutch. I need to know how these are wired into the circuit. BTW, thank you for your answer.

Karl

Thinking of your provided information, looks like I need to see if there is 12VDC at the coil terminal to eliminate at least part of the keyswitch. It also seems to me that any/all interlocks have to be in series with the keyswitch "Start" position and the starter solenoid. This way the mower will run with the key on but won't start unless all interlocks are made. Once the mower is running the interlocks can be ignored.

Karl

Here is just one wiring diagram. It's not a schematic, so it's somewhat useless for troubleshooting. - list# - PartsAndService - View Illustrated Parts Catalogues - ipl.cgi.v305 1 - (http://www.partsandservice.com/bin/ipl.cgi)

Other models are there too.

Usually the wire to the engine is grounded to stop the engine.

Note, it looks like there is a PTO (Power Take off ) switch, seat switch and a clutch basically wired in series.

Your appear to be Europe, so it made it harder. The schematic for the actual mower is on page 28 here: http://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=lgiqwEP.TFzXFix2

Page 40 might be better.