QuestionQUESTION: Thanks for this opportunity!
1997 Murray Lawn Tractor, Model No: 46560X92A, Briggs & Stratton 18HP Twin II, Model No: 42A707, Type: 1238 01, Code: 9605205B (tractor body/hood)says 17HP, Automatic Drive, but engine is labeled 18HP Twin II).
I'm assuming the diode is under the flywheel, so I have the upper "coverings" removed and am down to the flywheel itself with the huge nut on it. Luckily I have the correct socket for that nut, but not sure how to stabilize the flywheel to facilitate removing that nut - could eventually figure something out I suppose, but would appreciate the proper method from an expert (and that certainly seems to be you ). Also just wanting to make sure I'm on the right track for finding the diode (under the flywheel?).
I have a torque wrench (to 250 ft.lbs.) and wondering where I can find the torque spec when putting the flywheel nut back on. No owners manual available online, for free anyway (too old a model evidently, and Murray went out of business, but then you already no that...), or do I have to buy one from Briggs?
I have a Fluke automotive multimeter. Will the instructions found therein (the Fluke manual I mean) for testing automotive diodes, work for this diode?
I have reasonable reason to suspect the diode (even if I'm wrong, would just like the experience of locating it, removing it (if necessary), or at least eyeballing it, and testing it), but holding back on the "rest of the story" (too much to type, unecessarily, at this moment) till after I'm proven right or wrong, about the diode.
Sure grateful for your help, John
ANSWER: The diode is outside the flywheel so there is no need to remove the flywheel. If you wish to remove the flywheel, Briggs, Tecumseh and most auto supply stores sell a strap wrench to hold the flywheel while you remove the nut. You will have to remove the ignition coil to install the strap wrench and it usually takes 2 people...one to hold the strap wrench and the other to remove the flywheel nut. We use an air impact wrench at the shop to remove the nut...that way we do not have to use a strap wrench.
Getting back to the diode. You should see a wire, probably 2 wires on your system coming out from under the flywheel. The diode is actually in the wire harness on the engine side of the connector. Sometimes Briggs solder the diode in the connector itself. Does your engine have a regulator? You can tell if you have a regulator by tracing the wires from under the flywheel; if they connect to a module the you have a regulator and the diode(s) are in the regulator.
I'm guessing the battery is not charging? Is this correct? Check out this site to help identify your system so we know exactly which charging system you have.
http://www.briggsandstratton.com/miscpdfs/RNT/alternator_replacement.pdf
Let me know which one is on your engine. Also, you may have to scrape some paint off the wire to identify the wire color. Sometimes when they paint the engines the paint covers the wire.
Eric
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QUESTION: I've put some Hi-resolution pics on my website for you (links below), including a screen capture of the matching diagram (for my engine), from the ALTERNATOR IDENTIFICATION page (the link you sent me).
(in the "wiring_inside_console" pic, there's no fuse in the fuse holder, but it WAS in previously when I was trying to start it).
Also got hold of the wiring diagram for my engine's serial number - posted that also. Except for a wire color or two not corresponding to the diagram correctly, everything matches up with my wire paths, excepting...
the two yellow wires (tied together at the ignition terminal...top terminal when viewing the diagram) that leads to the connector which leads to the armature and an AFTERFIRE SOLENOID. I only have one yellow wire (from the pair at the top terminal on the key switch) that leads to the armature (coil?).
As for the rest of the story, I guess I should start at the beginning:
I'm trying to get this unit running again for a friend. He bought it recently, used, out of the classifieds I believe. He used it a few times this year, then it started emitting white smoke, so he parked it. One of his roommates tried using it later (didn't know about the smoke I guess) and it smoked again - he shut it off, and they delivered the tractor to me, subsequently.
When it arrived, it wouldn't yield any action or click noise at all, and the battery would not take any charge at all from my small Vector (Victor?) automatic, solid state battery charger - it gives an LED indication of FO2 (FAULT indication, of "will not take a charge", just in case you're familiar). Maybe a commercial charger would revive it?
I installed a new battery, and attempted starting it. The key switch didn't turn it over - no action at all, so I left the key in the RUN position, used the STARTER BUTTON somone had added to the console (which I thought initally might be a kill switch - not familiar with lawn tractors)
It turned it over normally, but wouldn't stop turning it over, so I scrambled to disconnect the battery. Starter seems to be ok afterward - it was engaged for what seemed like an eternity, but I was fairly quick at getting the batter disconnected - was afraid something was going to burn up.
To jump ahead just a bit, I later found the PTO SWITCH to be defective, if I interpret the electrical diagram correctly(when the mower engagement lever is pulled back (to disengage the mower), it depresses the PTO switch button, which should then read continuity (ohms test) between the two black lead postion lugs/tabs on the switch (switch disconnected from the circuit)...which would then relay power on to the start solenoid (assuming power is coming from the CLUTCH BRAKE SWITCH ok, which it was - I had the PARKING BRAKE on, and when I jumped those two black wire positions on the PTO switch, it would, indeed, turn over using the key switch, but wouldn't start.
I assume the start button was added because the former owner didn't know how, didn't want to learn how, or didn't want to sepnd the time looking for the NO START problem (using the key), caused by the faulty PTO SWITCH.
So, he wired the start button to the BAT and STARTER terminals on the solenoid (using 10 guage wire), when he should have wired it to the BAT terminal and SOLENOID primary circuit terminal at the base of the solenoid (a tab sticking up from the base).
When I removed the upper part of the console housing (and gas tank), I found the 10 guage wire used to add the starter, with it's insulation thoroughly fried (wire itself was ok). Upon inspection of the starter button, it was not sticking, but must have been - doesn't seem like anything else could do that to its insulation, and I guess that's the only thing that would keep that starter engaged for so long.
I also later found three nicks in three of the wires coming from the key switch. These nicks were all in alignment and being cut into (down to bare wire) by the PTO linkage (the heavy flat piece of steel linkage, on the inside of the console) - the wire bundle was below the linkage inside the console, which would cut right into to it when engaging the mover...pushing the lever arm forward in other words, moves the linkage (flatw steel piece) downward into the wires.
Those three wires were short circuited together, and they are:
The black wire (which is always hot) which also connects to the key switch terminal (red wire and black wired to together), that's connected to the fused red wire leading from the key switch to the BAT terminal of the solenoid, and....
one of the yellow wires (two connected together at the key switch) leading to the ignition module (coil itself?)....(this fried the coil maybe, if that's what it connects to...)
and a red wire which goes to the headlights.
Will be purchasing a new PTO SWITCH tommorrow morning if they have it in stock?
Coil fried (and battery drained) by the short circuit (linkage cutting into those wires)?
Thx, John/PlumDucky
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http://whengoodmendonothing.com/stator_connector_at_flywheel.jpg
http://whengoodmendonothing.com/wiring_inside_console.jpg
http://whengoodmendonothing.com/top_view_of_ign_module_and_wires_to_module_and_f
http://whengoodmendonothing.com/wiring.gif
http://whengoodmendonothing.com/alternator_identification_diagram.gif
AnswerThe diode is on the red lead. I have a special test lead adapter for my Fluke which I use to check the diodes. It basically pierces the insulation, pin hole size, so you don't have to remove the shrink tubing on the wire.
Did you see your key switch on the Briggs website? Are there any letters on your key switch, near the terminals?
Eric
