Welcome Mark!, I have a PDF of the Deere Tech manual for the LT155 you're welcome to,
if wanted shoot me your email

Joe

 

u can post a PDF here usin the manage attachments.. (this requires a scroll down to see it) that way all of us can get it.. & no buggin u with the E-mail bit..

on edit.. here is a PDF..

 

Joe--- Thanks! Much appreciated. I just hope I can make heads or tails of it. It seems like I read there could be more than one for this model, and I'm gonna be confused enough as it is..... If so, is there a way to make sure it's the right one? (serial #, etc). Just confused as to what's going on with the machine. It's in really GREAT condition and it'll be a big help on my huge lawn! Thanks again-- Mark (mkjohnsons@hotmail.com)

 

download link on the way shortly, this volume was issued September 20,2000 well after yours was built, so yours is in it

Joe

 

Just clarifying something for myself, does it crank and not start or just not crank with the diode out?

 

Typically, I think it's a common issue that resistance builds up in the safety switch connectors such that there is enough voltage drop that the solenoid won't engage when you turn the key switch. I had an STX38 like that... Anyway, I did the starter relay mod (should be able to search that one out) where you add a generic relay to actuate the solenoid. Worked for me!

 

Ah, here's the thread...

http://www.mytractorforum.com/280-s.../210940-using-starter-assist-relay-fix-kohler-command-click-no-start-issue.html

 

I mean if thats the case he can install his diode and disconnect the solenoid ground from the harness and run a frame ground in its place. But that circumvents the safeties . The starter positive is right off the key switch . If one of the other relays or switches isnt working it can keep the magneto grounded. Why i was wondering if its a no crank or just a no start. Edit: I see you keep all the safety switches with the secondary relay setup. Nice .

 

EMD-- Thanks for the reply! If I understood you--- "with the diode OUT". With it OUT it does not crank (or start). The headlights come on as the turning of the key "passes thru" the middle position on the ignition switch. And (even) with the new JD dealer part-- (that I assume is good) diode IN-- it's exactly the same thing...... ZIP/ nothing. Anyway--- to add to the weirdness, if I remove the diode "plug-in" piece (leaving just black wires in and black wire out of this connection, install a jumper across that "open", it cranks, starts, and runs like the day came from the factory! If that's not enough--- I can REMOVE the jumper after it's running, and it just keeps right on running just fine. Just as a test, I raised up off the seat, and the seat safety switch kills the engine whether the jumper is on there or not. To "wander" a little, and if it matters at all at this point-------- (and I'm making an assumption)------- this machine has a "3-position" ignition switch. There is "OFF", "ON" (sort of halfway-- the headlights come on), and "START". (I'm beginning think it's haunted.... or just PO'd it got sold to another owner!). Anyway-Thanks! Mark

 

Edit: I see you keep all the safety switches with the secondary relay setup. Nice .

Yeah, essentially what that secondary relay does is take the weakened voltage passing through the safety switches (that should be kicking the solenoid, but isn't), and uses it as its pilot voltage to switch itself on and provide full battery voltage to to the solenoid (instead of the weakened voltage). If you have a safety switch tripped, it will interrupt the pilot voltage to the secondary relay, so the safeties still work properly.

I suspect messing with the diode is a false path, but that's only my guess...:dunno:

 

& a PDF file

 

I believe this is the start of the old 318 starter relay kit where the resistance of the entire safety circuit has climbed to a point that with the diode in line there isn't enough voltage to activate the solenoid. I would look into just jumping the diode until the engine is running then removing the jumper and the safety switches would be back in play. One way to test this is to hook up the diode to a clean wire from the battery to the solenoid and if it runs and starts ok then it is a resistance issue. BTW, diodes do lose their values just like every other electrical component.

 

Here is a simple diagram to troubleshoot the no crank issue. The red is your normal start path. The blue is the start path you are using by jumping the diode. To troubleshoot , Start at the key switch grounds. They should have battery ground there . IF they dont move back towards your battery , if they do check your brake and pto switches. Im leaning towards something at the key switch , The engine should shutdown regardless of everything else with the key in the off position if the grounds are good at the switch and it is working correctly regardless of the diode or jumper.

Mike

 

the LT's had a 3 amp & a 15 amp system.. some machines have 2 relays.. some have 3.. & some have 4 of them..

the early LT's didn't have the yellow reverse button.. the later ones do..I have 3 JD LT 155's.. they all require a different wirin schmetic..

 

I agree that you should jump your tractor battery with a good strong car battery and see if it works then. If it does then you may have one of those batteries that appear to be fine but when the load is applied fail to provide the required amperage. If it won't crank with a known strong battery then you can go to work bypassing each safety switch or relay until it will. I know how frustrating electrical problems can be.

 

WOW!--- Thank you all for the thoughts/ experience/ & expertise! This is all lot to chew on. Like all good information, it prompts more questions!

Q- 1. Do the phrases "resistance of the entire safety circuit" and "high contact resistance" mean the same thing? Does that mean that resistance is occurring INSIDE the switches themselves, or does that maybe mean that where the switches PLUG IN to the "harness" could just be dirty, wher I could clean the out with a de-greaser spray, plug them in & out a few times, then apply electrical DE-OX, and plug them back in". I can redo all the "switch plug-ins" in only maybe 15 mins. Easy.

Q- 2. The circular TERMINATION ITSELF (at the "battery-end" of the "main" large, red wire going from the POS post of the battery to the large post on the solenoid) is about half gone. It's done. It is NOT even in a "full circle" anymore. Don't ask me how this happens..... Would simply replacing that whole conductor and terminations have ANY effect on my tractor issues? Easy peazy-- $20 and 1/2 hr.

Q- 3. Is the battery VOLTAGE a problem? W/ engine off it tends to hover around 12.4--12.6. W/ engine running it tends to hover around 12.6-- 12.7 or 8. If I "trickle-charge" it for little while, it naturally(?) is a little higher, hovering at around 13.2 or 2. I have another tractor (Craftsman, w/ 20HP Kohler). Can I take the battery out of that, trickle-charge it a bit, put it in my JD, and expect anything different in my JD-LT155?

Q- 4.-- How's this for a plan (just for a fun test). Radical-- yes. Can I just TEMPORARILY, but COMPLETELY rewire the whole tractor with only the most bare-bones wiring? It seems like that WITHOUT all the "safety-switch network", the most-very-basic wiring harness is pretty simple. Would that at least test all the basic, "large" components? (battery, ignition switch, solenoid, starter, stator, voltage regulator-rectifier, and coil?)???. Radical- yes. Temporary- yes. It may at least tell me where the problem ISN'T.(?)

Q-5.-- Sounds obscure, but, on my LT155, could a HEADLIGHT issue be some kind of tell-tale sign or signal of my issues? The RF headlight has gone out TWICE since the machine started having issues. Just coincidence?

Thanks again to ALL for your help & expertise. (My wife says, anyway, that) it's a curse that I am VERY analytical, experimental, and persistent, not afraid to get my hands dirty AT ALL. My actual mechanical skills are more like somewhere around a "B". I'll get 'er fixed. THAT'S for sure.. Thanks again------ Mark J

 

WOW!--- Thank you all for the thoughts/ experience/ & expertise! This is all lot to chew on. Like all good information, it prompts more questions!

Q- 1. Do the phrases "resistance of the entire safety circuit" and "high contact resistance" mean the same thing? Yes, sorta! The entire circuit would include wires, switches, relays and connectors. Any high resistance will "drop" voltage across that resistance point. If it is high enough, it could result in insufficient voltage to operate the starter solenoid. Does that mean that resistance is occurring INSIDE the switches themselves, or does that maybe mean that where the switches PLUG IN to the "harness" could just be dirty, wher I could clean the out with a de-greaser spray, plug them in & out a few times, then apply electrical DE-OX, and plug them back in". I can redo all the "switch plug-ins" in only maybe 15 mins. Easy.

Q- 2. The circular TERMINATION ITSELF (at the "battery-end" of the "main" large, red wire going from the POS post of the battery to the large post on the solenoid) is about half gone. It's done. It is NOT even in a "full circle" anymore. Again, all connections need to be clean and snug so you don't have a high resistance connection.Don't ask me how this happens..... Would simply replacing that whole conductor and terminations have ANY effect on my tractor issues? Easy peazy-- $20 and 1/2 hr.

Q- 3. Is the battery VOLTAGE a problem? W/ engine off it tends to hover around 12.4--12.6. W/ engine running it tends to hover around 12.6-- 12.7 or 8. Battery voltage of 12.6 is pretty normal, but it should be upwards of 13 to 14 when the engine is running. This could be a charging circuit issue or a bad battery. If I "trickle-charge" it for little while, it naturally(?) is a little higher, hovering at around 13.2 or 2. I have another tractor (Craftsman, w/ 20HP Kohler). Can I take the battery out of that, trickle-charge it a bit, put it in my JD, and expect anything different in my JD-LT155? Id really like to see what happens when you jumper your battery with a known good one.

Q- 4.-- How's this for a plan (just for a fun test). Radical-- yes. Can I just TEMPORARILY, but COMPLETELY rewire the whole tractor with only the most bare-bones wiring? It seems like that WITHOUT all the "safety-switch network", the most-very-basic wiring harness is pretty simple. Would that at least test all the basic, "large" components? (battery, ignition switch, solenoid, starter, stator, voltage regulator-rectifier, and coil?)???. Radical- yes. Temporary- yes. It may at least tell me where the problem ISN'T.(?) Nah. too much work. Better to just troubleshoot what you have.

Q-5.-- Sounds obscure, but, on my LT155, could a HEADLIGHT issue be some kind of tell-tale sign or signal of my issues? The RF headlight has gone out TWICE since the machine started having issues. Just coincidence? A lot of times, it is the connection to the headlight lamp socket. You don't have the lamp burning out, do you?

Thanks again to ALL for your help & expertise. (My wife says, anyway, that) it's a curse that I am VERY analytical, experimental, and persistent, not afraid to get my hands dirty AT ALL. My actual mechanical skills are more like somewhere around a "B". I'll get 'er fixed. THAT'S for sure.. Thanks again------ Mark J

I've been having trouble getting this to post. Let's see if this works.

 

Rudy--- Thank you.

Your thought-process here is WAY beyond my "normal operating range"!. I sort-of DO generally understand what you mean, though (I hope!?).

Can you please go over or repeat your last sentence (beginning w/ "One way to test this is to hook up the diode......". Can you be REALLY specific about how to hook up what to what and where to where. Are you talking about the "red/molded rubber" diode piece ITSELF (and... which side of it-- or TO which side of it). Or are you talking about the connection POINT (or points) that the diode piece plugs IN TO (it is BLACK molded rubber w/ 1 black wire "in", and one black wire "out".

How do I test it, and what are the results I WANT, and DON'T want?

I am very sorry, but as you can see, I am WAY more analytical than knowledgeable......

Your (and all your fellow contributors') help and advice is DEEPLY appreciated.

Sincerely- Mark J

 

Hello---

Sorry about replying "to myself", but something is bugging me.

Am I in any way "hurting" or damaging my tractor by jumpering-out that diode connector (or connection point), and starting it up (just testing things, taking voltages, etc).

The last thing I need is to make things worse trying to make things better.......

What is his diode thing anyway? What does it do? IF, (and I repeat-- IF), I can jumper-out that location (removing the diode thing completely from the system & circuit, why is it even there? I am REALLY sorry if that all sounds stupid.

Thanks--- Mark

 

Electrical is my KRYPTONITE!
Anything mechanical, no problem...

Sent from my SCH-I545 using Tapatalk

 

Do you have a meter or test light? And i know i asked and you answered about the diode out . What does it do with the diode in ? nothing still no crank ? If it only cranks when you jumper the diode you have a bad ground at the switch , pto safety , or brake switch . IF it is a connection issue contact cleaner should help. Get it into the switches and work them and pull the connectors and spray work them on and off , rinse repeat. Unles you have non-flammable cleaner let it evaporate before trying anything. Even if it is the wrong wiring diagram and you have more or less relays the start circuit should be the same . The diode keeps the starter from engaging by blocking the ground path if the pto were on and you were sitting in the seat. A test light whill help you find the problem in less than 5 min and i can help walk you through it if you need me too. I also have a 155 sitting here fr reference.

HAppy gremlin hunting,
Mike

 

Does the starter engage when you put 12v (say from the battery +terminal) to the small post on the solenoid?
If so, that would mean your solenoid isn't getting enough (or any) pilot voltage to kick it over.

I'd also put a meter on the wire that connects to the small post of the solenoid, and verify it gets 12v when the ignition switch is turned to start. If it gets none, you probably have a break in the safety circuit, which is basically between the ignition switch and the small solenoid post. Could be a bad switch, bad wire, or switch that's out of mechanical adjustment... It could also be a faulty ignition switch I guess... If you get partial voltage, then we're back to that voltage drop issue'that the secondary relay is meant to address.

 

I have a hunch you have the Fusible Link confused with a diode?
It's a FUSE.
I can't imagine WHY a diode would be used in the starting circuit.

A diode IS used in the 3 Amp charging systems to rectify the AC voltage from the stator.
It blocks the negative pulse of the AC Sine Wave, allowing a pulsating DCV through.

 

There are 3 diodes in the system. There are 2 blocking diodes and one rectifying diode. One misconception is the changeable diode on the battery charge wire is to rectify the voltage. The diode that rectifys the ac to dc is on the stator and not serviceable unless you remove the stator. The rectifying diode in this circuit , will need a blocking diode to keep battery from back feeding onto the stator while the engine isnt running, which blows the fusible link because when the stator isnt charging the backfeeding battery positive goes straight to ground through the stator. The diode on the starting circuit is there because it shares the ground at the pto switch and would backfeed to the starter solenoid ground and bypass the safety switch without it.

 

There are 3 diodes in the system. There are 2 blocking diodes and one rectifying diode. One misconception is the changeable diode on the battery charge wire is to rectify the voltage. The diode that rectifys the ac to dc is on the stator and not serviceable unless you remove the stator. A rectifying diode will need a blocking diode to keep battery from back feeding onto the stator while the engine isnt running, which blows the fusible link because when the stator isnt charging the backfeeding battery positive goes straight to ground through the stator. The diode on the starting circuit is there because it shares the ground at the pto switch and would backfeed to the starter solenoid ground and bypass the safety switch without it.

OOOOKKKK... now tell me Y the B & S engines have a diode to change A/C to D/C.. & the machines they r on do NOT have any other diodes on them..

u say....'''A rectifying diode will need a blocking diode to keep battery from back feeding onto the stator while the engine isnt running,"""

I disagree..


B & S has used the diode way back in the 60's.. with the half moon stater.. & the full circle ones..

 

If it were wired different or briggs built it maybe it would only need one . If you give me a wiring diagram i might can tell you why also. Why do you think it frys the fusible link when you jump the diode? But we can agree to disagree i suppose.

 

JD used B & S engines on the 100 round fendered machines made in the 70's.. these had a fuse.. they didn't blow each time they were shut off.. they also had no backfeed.. if they did the battery would drain..

on edit..u said this.. I disagreed with that..

A rectifying diode will need a blocking diode to keep battery from back feeding onto the stator while the engine isnt running,

 

Whirly is correct on the use of a blocking diode to keep the battery from discharging if there is not a way to break the connection of the circuit and battery. (Like a key switch, or relay).

It is just a cheaper way of building only what is basically needed to function. (No bells, whistle, etc)

 

Actually i was making that statement. He disagreed with that. My original statement was really pertaining to this particular problem on the op's machine.

 

YES BUT u made the statement & I will quote it again..

.'''A rectifying diode will need a blocking diode to keep battery from back feeding onto the stator while the engine isnt running,"""

that is not true.. & I stated where it wasn't needed since way back when..

ALSO there is not a ''rectifying diode ''.. cause a diode is part of a rectifier.. a diode permits A/C current to b turned into D/C cause it permits half of the sinewave to pass thro it..

a single diode is not called a ''rectifying diode ''

 

Come on guys...
"Can't we all just get along?!"

Agree to Disagree and see if someone has a potentially solve this electrical issue.

-Thomas (12)
Just west of Seattle, Washington

Sent from my SCH-I545 using Tapatalk

 

in the attachment that emdmechanic posted the extra diodes r used to prevent a backflow to other parts of the circuit.. NOT the stator as he posted..

on edit.. actually the first diode in the line from the stator prevents any backflow to the stater ..