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Hello all, Jim from CT here. Been banging my head against the wall for weeks now trying to get this mower to turn over. It is a craftsman model 536.270320 mid engine rider. Turn the key to starting position and nothing happens, not even a click. Installed new solenoid, swapped out starter from another rider which I know is good, replaced safety switch under the seat, checked entire wire harness and no cuts or breaks, tested both pto safety switch and the brake safety switch with an ohm meter, both have continuity. I don't know anything else I could check. Also put new fuse in as well as another ignition switch. What's left??? Is this solenoid wired correctly? Can the black wire from the harness share the same ground as the neg battery terminal as shown below? Red wire on right goes to starter, red wire on left goes to pos battery terminal.

Start from the top.
1) check that the engine actually rotates by rotating it by hand.
2) Measure the voltage between the battery terminal on the solenoid and the ground.
If you ain't got 12 V here you ain't got nothing.
3) Bridge the two terminals on the top of the solenoid.
Starter dosn't turn then the battery or the battery terminals are suspect.
4) run jumpers from the battery directly to the starter terminal on the solenoid
Engine should crank, if not the ground cable is bad.

Try a known good battery.


It matters not where the ground terminal attaches to.
However as the starter motor is the heaviest current draw, I always reroute it to one of the starter motor mounting bolts even if that means runinng a new ground or secondary ground.


Finally

THE SEAT SWITCH HAS ABSOLUTELY NOTHING TO DO WITH THE ENGINE STARTING SO LEAVE IT BLOODY WELL ALONE

http://www.searspartsdirect.com/mod...=modelSearch&q=536270320&searchTerm=536270320

wiring looks good, remove battery & take to local auto parts store for load test, should be of no cost to you

check spark plug wire for being loose on plug or disconnected

Battery is good, reading 12.7 volts. Jump from solenoid to starter will turn the starter. Also tried a second battery that I know is good and still nothing. Engine rotates by hand just fine. This happenned all of a sudden. It was being used and was running, turned off for 20 min to eat lunch and came back and everything dead.

"2) Measure the voltage between the battery terminal on the solenoid and the ground."

...so just take red probe on my multimeter and touch the pos terminal on the solenoid, and touch the black probe to the ground screw in the frame?

Yes, but if the starter works when you bridge the two terminals on the solenoid one can safely assume you have a good connection to the solenoid.

So the wire from the hot terminal to the ignition switch will now be the prime suspect.
It should have a fuse in it.
Check for voltage at both side of the fuse holder then at the B terminal on the ignition switch.

Fuse is good, tried about 5 brand new one's just to be sure. How would I check voltage at fuse holder or B terminal at ignition switch? Red probe to B and black probe to G? Do I need to have parking brake on and key turned all the way to start position at the same time?

BTW , red probe to positive terminal on solenoid and black probe to ground reads 12.74 V.

excalibur2 said:

Fuse is good, tried about 5 brand new one's just to be sure. How would I check voltage at fuse holder or B terminal at ignition switch? Red probe to B and black probe to G? Do I need to have parking brake on and key turned all the way to start position at the same time?

Click to expand...

Basic mower wiring
Battery- solenoid terminal-fuse- B terminal ignition switch - S terminal ignition switch - Pto switch - parking brake switch - trigger terminal on solenoid- ground
Somewhere in that chain above is a broken link.
I like to use a test lamp that has a clip on one end so I have a spare hand to pull wires & work switches.

ok, I'm getting 12.74 volts at the fuse terminal, now what?

excalibur2 said:

ok, I'm getting 12.74 volts at the fuse terminal, now what?

Click to expand...

So carry on along the chain,
Ceeck the output side of the fuse then the B terminal on the ignition switch, the S terminal etc etc.
Somewhere between the red wire and the orange wire there is a break in the wiring,

somewhere along the lines testing all this stuff i managed to blow the fuse.{just noticed} Put a new one in and still dead. All wiring looks like new, I peeled quite a bit of the wiring from the corrugated jacket from the brake switch end all the way up to the solenoid end. I don't see any breaks or cuts anywhere

Seeing is not testing.
Every wire in the cranking circuit.
Both sides of every switch
One of them is bad.
Be methodical
Input side & output side
Switch open & switch closed.

We has someone here a while back that he had ants in his PTO switch which caused random no starts when they got stuck under the sliding blade on the switch.

I know it is a PIA, my backside stings regularly trying to sort these things out.

Fairies & gremlins do not exist, electron do
And some where between the terminal on the red wire and the terminal on the orange wire there is a hole and the smoke is getting out.

I do appreciate all the help, but my knowledge of electrical testing only goes so far. Can a switch be bad even though the continuity tests good? Could the kill wire have anything to do with a no crank situation? this is driving me nuts. Trying to help out a friend { it actually belongs to him}, I'd hate to tell him I can't fix it, and at this point it's become a personal obsession lol.

excalibur2 said:

I do appreciate all the help, but my knowledge of electrical testing only goes so far. Can a switch be bad even though the continuity tests good? Could the kill wire have anything to do with a no crank situation? this is driving me nuts. Trying to help out a friend { it actually belongs to him}, I'd hate to tell him I can't fix it, and at this point it's become a personal obsession lol.

Click to expand...

No the kill wire has nothing to do with the cranking circuit.
I have already told you what the circuit is.
Continuity testing sort of works but a test lamp works better.
Poke the probe up the bum of the plugs to get contact with the wire.
It is really not hard, just follow the wire from one end to the other,
Tedious, yes
Frustrating yes
hard no

I have a test lamp and aside from touching the probe to battery side of solenoid post and ground clip to ground screw and getting the beep and the light, I'm really not sure how to use this tool to continue the entire circuit test for voltage { touch probe to where, negative clip to where, does key have to be turned all the way, does brake need to be on, does operator need to be on the seat, etc, etc. I did use another tool I have to test voltage in the fuse socket { multimeter } which read 12.7. The continuity tests I tend to understand a bit better - one probe to one end of anything metal and the other probe to the other end. If it reads zero's or anything ever so slightly above, it's good and will complete a circuit. Now as far as voltage testing I'm just not that experienced.

Exactly the same way.
Leave the clip connected to a good ground.
Anything you touch with the probe that is live will make it glow & beep ( you have a good one ).
So you start the probe at the solenoid terminal then go up the red wire and push the probe into the back of each side of the fuse holder.
Again it should beep.
Follow that wire up to the ignition switch and poke the probe into the back of every wire in the terminal block.
With the ignition off only one wire should beep ( the one from the fuse ).
Get a strong magnifier and look at the back of the old switch.You should see tiny letters
G = ground
M = Magneto
B = Battery ( should be connected to the fuse )
S = Start
A = Alternator
L = Lights ( fuel solenoid is generally connected to here )

Some will have 2 L and or 2 A terminals

Now back to the mower.
All you are interested in right now is the cranking circuit so push your probe into the back of the S terminal while holding the key in the start position.
You can do it to all the terminals in the off, on and start for the heck of it if that will make the actions of the switch clearer.
Follow the wire from the S terminal to its next switch, should be the PTO ( Switch if electric PTO , safety switch if a lever PTO ).
Here you will need 3 hands because you need to test the wires with the ignition in the start position and the PTO both on and off.
You will find it easier if you pull the plug on the ignition switch off and poke a short jumper between the B & S wires on the plug.
IF the pto switch passes power through it in the off position, follow the wire , It should now go to the parking brake.
Same proceedure.
Mechanical gear box mowers will also have a reverse safety switch in the cranking circuit, hydros don't.
Eventually the wire will come back to the solenoid.
Some of the safety switches will have 4 or even 6 wires , 2 will be coloured and the rest will be black, brown or white with or without a stripe.
All the similar wires will be part of the magneto cut out and are not part of this test ( they will either be ground or open )
On some mowers the wire changes colour every time it goes through a switch while others it will be the same colour from the S terminal on the ignition switch all the way through ( usually yellow or orange )
Keep a note pad with you and write down the colours as well as weather it was live ( beep & lights ) when the switch was on or off.

If a wire is broken where the terminal crimps on and you poke your probe into the back of the plug, it might cause the broken wire to make contact which will crank the engine if you have jumped the plug on the back of the ignition switch,
Be ready for it as it can suprise you and do not put anything on top of the engine nor lean on it.

Somewhere from the red wire on top of the starter solenoid to the orange wire which triggers the starter solenoid there is a broken connection.
Double check that the orange wire does not have 12V on it when you turn the key to the start position.
If the orange wire goes live when you turn the key the solenoid is the problem.

Ok that makes more sense to me, I will lick this issue yet. One thing though:

" check that the orange wire does not have 12V on it when you turn the key to the start position.
If the orange wire goes live when you turn the key the solenoid is the problem."

I thought that if i connect my neg clip from test light and touch the probe on the small spade terminal on the base of the solenoid { orange wire}, I am supposed to get 12v. Isn't that orange wire the same wire that sends a signal from the ignition switch to tell the solenoid to do it's job and crank the starter??

Sorry, badly written.
With a known good fuse in the red wire, check the orange wire for 12V when the ignition switch turned to start.
Yes you are correct it is the orange wire that makes the solenoid switch the juice to the starter motor.
So we should check that before you go digging through the rest of the wiring to confirm there is a problem with that circuit.
When I re read the the whole post I noticed I had assumed the orange wire was at fault but we had never actually checked it.

Ok here's the latest: Will check orange wire soon as I get a second person, seems I need 6 arms for this test! Anyway, for 16.00 i purchased the 2 switches today. PTO switch and brake/clutch switch. Still nothing, completely dead. Removed entire harness from tractor, went over every inch of every wire with a magnifying glass, no cuts or breaks. Tested continuity from one end to the other on every wire, every lug and hole, all tested 00000 or very slightly above. Just curious, I am wondering if there is an engine ground wire hidden somewhere? At least I can rule out all switches { except reverse safety switch which even if bad would still allow engine to crank providing blades are not engaged}, so in a nutshell it must be something much simpler, especially when the mower was running one minute and ten minutes later she went completely dead.

You bridged the two terminals on top of the solenoid & the engine cranked then the ground contact is reasonable.
If you jump to the orange wire & the engine cranks then the ground is OK. and the solenoid is OK
This is why you then have to go and check the wiring in the mower.
From memory you already changed the ignition switch so that is ruled out.
This leaves the PTO, Clutch/brake & reverse if you have a manual gearbox.

Can a bad diode have anything to with a no crank situation? Also, how is the starter grounded?

excalibur2 said:

Can a bad diode have anything to with a no crank situation? Also, how is the starter grounded?

Click to expand...

Once again,
The cranking circuit & the ignition circuit are two different animals.
Nothing in the ignition circuit will prevent the engine cranking with the exception of a totally stuffed ignition switch.
Nothing in the cranking circuit will prevent the engine firing , again apart from a totally duff ignition switch.

Your problem is in the loop red wire through to orange wire

Starter grounds through the mounting bolts to the engine and the contact patch where the starter body touches the engine crankcase.
Engine grounds through the 4 mounting bolts.
On some slow cranking engines I run a ground wire from the main ground a the starter motor mounting bolt.
Generally these are mowers that live out in the weather

I have power!!! No idea what the issue was though. Tonight I had the entire harness on my workbench, the only thing I did before reinstalling is remove a couple of the metal terminals from the ignition connector, they are a bit tricky to find the tab to bend them back and slide the terminals out. Once out, i sprayed them with electronic cleaner and scrubbed with a toothbrush. Funny thing is they really didn't look horrible. Reinstalled the terminals. Removed terminals from fuse connector, did the same with the spray. Tightened the metal tabs that hug the 2 fuse blades, one was not very snug. Cut end of orange wire off where it connects to the solenoid, stripped to clean wire and crimped on a new ring terminal. Reinstalled harness, solenoid, battery cables, starter cable, switches and heard this funny cranking noise I did not expect! Wife was getting concerned the last 2 weeks with me acting like a mad scientist in the basement. Now to change the oil and give her a good scrubbin and will return to buddy. Thanks a million for all your help and patience! Just wish I knew exactly what it was that I did tonight that made the connection.

...I still say there was a gremlin in there

Removing terminals & replacing them cleans the contact area.
Obviously the terminal on the orange wire was bad.

Only 1 thing really matters, it goes Brooooom

Ok perhaps I celebrated a bit too soon. When I got it to crank, the tractor was in my basement so I did not go all the way to see if it actually started. So yesterday I got it all back together, pushed back outside, changed oil, etc and went to start it. Cranks fine now but no spark whatsoever. Tried another coil I borrowed off another rider, still no spark, which leads me to believe the issue exists in the thin black wire going to the coil, any suggestions as to how to troubleshoot this wire? There are no bare spots on it so not sure what else it could be.

Remove the thin black wire
It is a kill wire that connects to ground.
If you have a spark with it removed then you have a safety switch problem.
If you don't get a spark with it removed check the black wire for voltage .
If you have put 12V down there for even the smallest amount of time you will have fried the magneto

Not sure what you mean by " If you have put 12V down there for even the smallest amount of time you will have fried the magneto"

Can you describe a scenario ?

I did test both magnetos on the ohm meter, both read around 4.65 which I think is good. In the meantime I'll test for spark with the ground wire off.

excalibur2 said:

Not sure what you mean by " If you have put 12V down there for even the smallest amount of time you will have fried the magneto"

Can you describe a scenario ?

I did test both magnetos on the ohm meter, both read around 4.65 which I think is good. In the meantime I'll test for spark with the ground wire off.

Click to expand...

YOU CAN NOT TEST A SELF CONTROLLED MAGNETO WITH AN OHM METER AND SOME CHEAPER ONES CAN ACTUALLY FRY THEM

The kill wire grounds out the micro chip in the magneto.
If at any time you have accidentially connected the kill wires ANYWHERE in the mower's wiring to 12 V, you can fry the chip.
For this reason, workshops always back test connectors so there is no chance the probe accidentially bridged a power wire with a magneto ground wire.
You will not see or hear this happen, the tiniest of sparks, then the chip is burned out so no further sparks.

This is why coils are not returnable.
I had a customer who fried 4 of them ( $ 300 worth ) before he brought the mower in for repair at the shop up the road.
They sent him to me ( gee thanks ) and I finally found a cross wired brake switch.
I have known customers using $ 5 mulitmeters, fry magneto chips when doing OHM testing because the meter sends power down the probe and measures the voltage drop at the other end to determine the resisitance ( ohms ).
For this reason I use a test lamp or a volt meter because the voltage function is passive and simply reads the voltage either side of a really big resistor in the meter.

Not trying to be insulting, but blokes buy a multimeter who have less than zero idea about how they actually work, then go shoving the probes everywhere where they should not go and at worst end up totally confused and at worst, do real damage to the mower.

Electricity is very simple, however it is taught very poorly and because of the litany of funny names, and the insistance of using the water in a pipe analogy most blokes blank it out.
At best they remember the Ohms law triangle so they can answer a few exam questions then blank it out of their minds forever.
Parents never buy children electronics play sets because they think having their computer literate kids wearing a smart watch than can run the TV of the internet will not be amused by joining up some wires and hearing a radio station so children never understand the basics.
The nephews built a calculator with ferrite loops and were over the moon when they managed to get it to add subtract and even better multiply.
And believe it not not, the one with really bad maths ended up in the top class because he finally got into his head they multiplication is nothing more than repetative adding and division is repetative subtraction

ahhh, ok. Not sure if it makes a difference but I removed the magneto completely off the machine and I bench tested it with a small ohm meter that takes a small cell battery, like a watch battery.

No you have not tested anything.
All you have done is shoved a probe in and got a number which has no meaning whatsoever.
There are two sets of windings in a coil and you gave one number further suggesting you don't have a feintest idea of what you are doing.
The circuits in the meter transform that 3 V into thousands of volts so the battery size is irrevelant.

"There are two sets of windings in a coil and you gave one number further suggesting you don't have a feintest idea of what you are doing."

Of course I don't know what I'm doing, this is why I posted the issue on this forum in the first place, but at least I'm giving it hell in the process!

Anyway, pulled connector to magneto off and cranked over, yes I am getting spark. With connector back on no spark. So the only safety switch I have not replaced is the reverse switch but I'm doubtful that has much to do with it.

I really am not trying to sound superior, but what works best is people ask you to do something and you do what you are asked to do then report back the results.
There are 2 benefits in doing things that way.
1) people who like to do things for themselves get a clear idea about how to go about the task
2) others who are following the thread who know what to do will chime in if the person rendering the help makes a mistake or misses something.
There is a funny sort of ettique where one person will take up a problem and the other techs just watch from the sidelines unless they feel something requires an itervention.
Everyone is more than happy to explain why you get asked to do something , however most who post don't really care why, they just want to go out and mow asap.

In this case you are now where you could have been a lot earlier had you have just tried it with the plug disconnected.

The reverse switch earths out the magneto when the PTO is on.
So next step is to turn the PTO on & off a few times . make sure it is off then try for a spark again.
Good news is the magneto is not fried. apparently they are not bad with a strong garlic sauce :laughing:

Now the kill circuit is a different animal.
The kill circuit works by connecting the wire you just removed to ground and to make things really complicated, there is a few of them all working in parallel but they do that in pairs
In the starting mode
Reverse + PTO ( not in all cases )
Brake + PTO
In mow mode
Brake + Seat
Reverse + PTO
Seat + PTO

So now grab they multimeter and check for continuity
Work backwards from the magneto wire.
test both side of each plug with the switch in both on & off positions.
Then pull the plug off the switch & test the wires in the plug again

Also remember that this is a ground circuit so it will be either open or ground but a short to the frame, pinched wire etc will not blow a fuse so you also have to test each wire, from plug terminal to plug terminal.
It is very common for this wire to strip where it passes through or under the heat shield around the cylinder which is doubly hard to find because every time you touch the wire, it changes.
Do all the testing with the wire off at the magneto end, remembering some of the switches with 4 wires on them can be live

Ok now here's a twist - I'll get spark with small black wire connected to armature only when seat safety switch plunger is in the UP position. Press plunger down { as if a rider were on the seat} and no spark. Seems this is working the opposite of the way it's supposed to. With seat switch disconnected from harness I get continuity with plunger down but no continuity with it up, which is the way it's supposed to work. Now if I plug it back into the harness it works the total opposite way.

Shown here is continuity with plunger not depressed, as if rider were OFF mower seat, as it should read on a properly working switch





And shown here is continuity with plunger pressed in, as it should. So when reinstalling the switch into the harness connector it's working the total opposite way. Strange.

Now I am getting spark with spark plug grounded to head with seat switch both in and out. Negative battery cable also heating up a bit. Has to be a ground issue somewhere

If the wires going into the ground terminal look grotty & corroded then there is a good CHANCE that there is significant corrosion inside the terminal.
You can try a jumper lead from the battery neg to a good grounding point. close to the starter.

As stated before the seat switch is not in circuit while the engine is cranking as you have now verified.

The worry is if the engine is cranking and the magneto is firing is the engine running ?
If not try a little fuel in the carb, starter spray is easiest to use, just don't overdo it.

I cut off the ring terminals on each end of the neg cable. One looked clean, the other end dirty and oxidized. Crimped on 2 new ring terminals, will put back together tonight. Will also clean area underneath solenoid mount for better ground. Now that I have spark, I have not tried to actually start the engine just yet - I'm first trying to determine why i'm getting spark { with spark plug out of head, grounded to block} with seat switch in either up or down position before i put everything back together. One minute the seat switch works the opposite way as it should be, next minute spark in both positions. Just one of those things where i gotta find out why, for my own sanity lol!

Ok I couldn't wait so I just reconnected the neg cable with the newly crimped ring terminals. Fired right up! Now, if I could just figure out why the seat switch will allow the rider to start the engine in either position. Being it will START now I should just leave it alone. One thing I did do first thing this morning is remove the internal spring grounding clip inside the harness connector where the seat switch plugs into. The 2 blades on the switch were hard going into the harness connector at times and it seemed these 2 internal spring loaded grounding prongs were interfering with a snug fit of the switch. My gut feeling says the manufacturer added this grounding clip to prevent everyone from bypassing the seat switch by simply unplugging it from the harness. When working properly, with this device in, if you disconnect the seat switch, the 2 clips spring back and short out the circuit and prevent starting. Being I had spark in either position before removing this clip, I'm thinking a new harness connector is in order.

BECAUSE THE SEAT SWITCH IS NOT PART OF THE STARTING CIRCUIT
So it will start with the seat switch in any position.
However if you let the parking brake off without being in the seat it will kill the engine.