2010 Murray Electrical issue

[BGS Mex]

The red wire at the ign switch plug is the 12 volt feed not the white wire. Put a test light at back side of wire harness and turn key to is if switch is sending voltage out to starter solenoid. If power is coming out of switch test at starter solenoid the same way. If good there make sure ground wire to solenoid is on

Hi: This is a new switch. I have even tested (OK) the start solenoid, and tried another from an operational (Husqvarna) tractor. Yes; the red (letter B) on the switch is 12V feeding the switch. The White (S) is to the Start solenoid (Power) terminal. Both "main" grounds are fine. When I run 12 V direct from the battery to this white (solenoid) terminal the solenoid activates and powers the starter. When the ign. switch is turned to Start (S) there is 8.46 V there and the white solenoid conductor has 11.46 V (?). The battery reads 12.70 volts. I have an operational Husqvarna in the shop and I tried this Ignition Switch and it too tested 8.5 V at the "S" terminal. Both ignition switches work fine on the Husqvarna and test at 12.68 Volts. Both Solenoids work too!
Thank you: I am at a loss with this thing. I have been unable to find a correct Murray Electrical schematic and the one from the parts manual is pretty useless. I have been a licensed Canadian Mechanic for many decades and am embarrassed by this! I'm "retired" here in Mexico; I mostly do PWC's, outboards (Yamaha) and light construction equipment; there aren't many tractors sold here.

 

[Auto Doc's]

Hi BGS mex,

For true load testing, rig an old round incandescent head lamp and use it for load testing the wires.

Ohm testing can fool you into thinking a wire is good even if it only has 1 strand left, but it cannot carry the needed Amperage. A small test light has almost no load.

Another method is to connect your meter while set to "V" to each end of a wire and see if it read voltage when you activate a circuit. If it reads voltage there is a problem with a connection or the wire

I did not see your battery ground cable in the picture. Check where it is bolted to the chassis to make sure it is clean and tight. I've seen a lot of bad chassis grounds on riders.

Last but not least, check the fuse holder for loose pin fit to the fuse or if they have been heated up a lot.

I always like to say: "The smaller the machine, the bigger the problem can be to find".

Short story:

I had a Husqvarna 20YTH46 rider a while back that had me stumped for 2 days until I found that the ground for the start solenoid had broken at the crimp fitting for the headlamp harness connector. The 2 grounds were crimped together with the harness ground and then doubled back to the start solenoid. I had to open up the harness jacket tubing to finally find the solenoid ground wire loose down inside the tubing.