Burnt wires, no start

[Sod 9]

I recently bought 520H from my neighbor. It ran okay few times, now it won't even crank (no dash lights). I think It has something to do with the burnt wire. It was like that when I got it but since the tractor ran I thought it would be okay. Looks like its shorting out. I put new battery today and it cranked few times then I could see smoke coming out of battery positive connector and connector was getting really hot. How can I fix it? Is this something I can do myself? Thank you

Edited May 6, 2021 by Sod
grammar

[squonk 41,118]

You are going to have to follow those wires all the way back and start at the beginning. That scrappy connection is known to fail. @rmaynard sells the connection

 

[953 nut 55,229]

The nine pin connector is a problem that can be remedied by anyone with some basic tools and a bit of common since.  The connector itself is not needed and was installed at the factory to reduce the time needed to assemble the tractor. If you carefully remove one wire at a time and use a good quality (read this as NAPA not Harbor Freight) assortment of wire terminals and crimper. Most of the wires will be 16 gauge and 12 gauge and you can get it at NAPA or other auto parts stores. 

Look under the seat to find your model number and we can fix you up with a proper wiring diagram.

[Ed Kennell 38,175]

This is one wiring issue that will be easy to find.  

 

[Sod 9]

1 hour ago, 953 nut said:

The nine pin connector is a problem that can be remedied by anyone with some basic tools and a bit of common since.  The connector itself is not needed and was installed at the factory to reduce the time needed to assemble the tractor. If you carefully remove one wire at a time and use a good quality (read this as NAPA not Harbor Freight) assortment of wire terminals and crimper. Most of the wires will be 16 gauge and 12 gauge and you can get it at NAPA or other auto parts stores. 

Look under the seat to find your model number and we can fix you up with a proper wiring diagram.

 

 

That's a great idea. I know the unburnt connector part is long enough to connect to other side even after I cut out all the burnt parts. Before that, I was thinking if I have to find female 9 pin connector and fix it that way. With your suggestion, I can just cut both connectors + burnt parts then connect / crimp them together. Wonderful! I'll put model number here soon so you guys can let me know which ones should connect to where. Thanks again!

[lynnmor 7,306]

Looks like those wires are melted for quite a ways and you will need to go back till where it is good.  I believe that you might have an exhaust leak that might be adding to the problem.  Do one wire at a time to avoid confusion, not all of the wires have the same color on both sides of the connector.  I repaired a couple of tractors by totally eliminating the connector and soldered the wires, then used heat shrink tubing for insulation.

[Sod 9]

10 hours ago, lynnmor said:

Looks like those wires are melted for quite a ways and you will need to go back till where it is good.  I believe that you might have an exhaust leak that might be adding to the problem.  Do one wire at a time to avoid confusion, not all of the wires have the same color on both sides of the connector.  I repaired a couple of tractors by totally eliminating the connector and soldered the wires, then used heat shrink tubing for insulation.

Should I start with same color wires? Does all color wires match? Thank you

[953 nut 55,229]

As long as you take your time and do one wire at a time the color of the wire isn't important. Be sure the wire you install is as big or bigger than the one it replaces.

[peter lena 8,627]

SOD, agree with others above on a rewire , as you recover sections , verify that you still have power , as you go along, so you do not loose it at a hidden spot. eliminate tight or possible chafing spots , use a " wire wrap " to contain your wires , use dielectric grease on slide on and grounding points , add additional grounding between engine and battery , and battery ground rail . actually , while your start looks horrible , its easier to recover and replace. I used "  small alligator wire clips  "  to run as my next  section , to verify flow and function , then add new. let us know how you make out , pete

[lynnmor 7,306]

 

1 hour ago, Sod said:

Should I start with same color wires? Does all color wires match?

 

That is why I wrote this: not all of the wires have the same color on both sides of the connector

[Sod 9]

It was pretty time consuming but I think I made some progress today. Slowly and carefully separated 9 wires so I can see which ones connects to where and labeled them. Next cutting connectors and bad parts out and join the wires. Thank you everyone for advice. I’ll keep updating of my progress here. 

[lynnmor 7,306]

I think that you get the award for the worst electrical meltdown on this forum.

 

Here is the colors that I found on one tractor:

[tom2p 2,394]

4 hours ago, Sod said:

It was pretty time consuming but I think I made some progress today. Slowly and carefully separated 9 wires so I can see which ones connects to where and labeled them. Next cutting connectors and bad parts out and join the wires. Thank you everyone for advice. I’ll keep updating of my progress here. 

yikes 

 

and some of those wires lead to expensive ignition components 

 

[Sod 9]

So I connected the wires. I was very careful to connect the same wires. I didn’t bother with soldering and shrink tube for now because I wanted to see if it actually works.  
 

Well it’s doesn’t  Engine does crank every times now but no start.

 

Also seat switch light is the only dash light comes on. Seat switch is already bypassed by previous owner looks like.
 

Dash lights worked fine until week ago then when mower didn’t start, dash lights stopped working and switch light was also only light was on. 
 

Not sure what’s next, I was so hopeful. Maybe there is something else other than melted wires caused the issue before? 

[Handy Don 12,232]

I think you've answered your own question. Something caused the wires to melt and you haven't found that yet.

3 hours ago, Sod said:

I'm guessing that orange wire nut is the PO's cutout of the seat switch. If he'd done it "right", the Seat Light would NEVER come on in the dash (the light is to tell you the seat is unoccupied when the tractor wants there to be a butt in the seat--the jumper is intended to make it look there is ALWAYS one there). Just one issue, but this could be keeping the engine from running.

 

I'm trying to think of how to fry all those wires--it takes either a lot of current, or they were up against a hot exhaust manifold or muffler. Most of the circuitry on a WH is protected by fuses which would blow WAY before that kind of damage could occur but as noted above, once things start shorting out, it can damage other things like the electronics in the dash panel, the gauges, or the electronics of the ignition system. Heck, it could even burn the contacts in the ignition switch which is designed for low-current 12v electric service.

 

I'd start with the fuses. Not blown, clean connections?

Then I'll look over all the wiring near the engine for any frayed insulation on wires or other signs of short circuits.

Then the ignition switch (remove the plug connector, test that all the pins are connecting correctly at the different key positions, check for clean connections, then put it back and look to see if 12v is getting to the B+ terminal (it's cranking so it seems yes).

Then, using the wiring diagram, start looking for 12v where it is supposed to be in the starting and ignition circuits (for example the + side of the coil when ignition switch is in RUN) -- since it is cranking, the starter circuit seems adequate for now (though it'll deserve having all of its electrical connections checked and cleaned at some point soon).

BTW, you do know that the motion lever must be in neutral and the PTO lever disengaged to start the tractor, right (sorry if I'm telling you stuff you already know). The switches that detect those settings will be next on your list, though they normally stop the engine from cranking, not from starting once cranked.

[lynnmor 7,306]

Use the Demystification Guide to troubleshoot the wiring.  There are a few errors in the guide, so watch for that.  Obviously the seat switch circuit is an issue, as stated above the light would not come on if the switch is really bypassed.  That high load from the wires being shorted may have overloaded the relays.  The Onan Manual has the tests for the ignition system, so follow the instructions there to see if repairs are needed on the engine.

[gwest_ca-(File Mod) 11,045]

On 5/7/2021 at 8:17 PM, lynnmor said:

I think that you get the award for the worst electrical meltdown on this forum.

 

Here is the colors that I found on one tractor:

This wire color list appears to match the original wiring diagrams for the 1991-1997 520-H. All other Onan twin diagrams are different.

The only difference is a black wire both sides of the 9-pin connector that goes from the oil pressure switch to the hour meter to ground the meter when oil pressure is present.

Click on the picture in the link to view it.

Garry

[Sod 9]

12 hours ago, Handy Don said:

I think you've answered your own question. Something caused the wires to melt and you haven't found that yet.

I'm guessing that orange wire nut is the PO's cutout of the seat switch. If he'd done it "right", the Seat Light would NEVER come on in the dash (the light is to tell you the seat is unoccupied when the tractor wants there to be a butt in the seat--the jumper is intended to make it look there is ALWAYS one there). Just one issue, but this could be keeping the engine from running.

 

I'm trying to think of how to fry all those wires--it takes either a lot of current, or they were up against a hot exhaust manifold or muffler. Most of the circuitry on a WH is protected by fuses which would blow WAY before that kind of damage could occur but as noted above, once things start shorting out, it can damage other things like the electronics in the dash panel, the gauges, or the electronics of the ignition system. Heck, it could even burn the contacts in the ignition switch which is designed for low-current 12v electric service.

 

I'd start with the fuses. Not blown, clean connections?

Then I'll look over all the wiring near the engine for any frayed insulation on wires or other signs of short circuits.

Then the ignition switch (remove the plug connector, test that all the pins are connecting correctly at the different key positions, check for clean connections, then put it back and look to see if 12v is getting to the B+ terminal (it's cranking so it seems yes).

Then, using the wiring diagram, start looking for 12v where it is supposed to be in the starting and ignition circuits (for example the + side of the coil when ignition switch is in RUN) -- since it is cranking, the starter circuit seems adequate for now (though it'll deserve having all of its electrical connections checked and cleaned at some point soon).

BTW, you do know that the motion lever must be in neutral and the PTO lever disengaged to start the tractor, right (sorry if I'm telling you stuff you already know). The switches that detect those settings will be next on your list, though they normally stop the engine from cranking, not from starting once cranked.

Thank you for the reply. I should clarify exact timeline and description of what happened.
 

1. When I bought it, tractor started okay(did crank few times before it would start). Previous owner said I should leave the battery disconnected

2. Wires and connectors looked like burnt from outside from being too close to exhaust manifold but since it started okay I didn't ask much about it

3. Also at first, all dash lights were working fine, all lights came on(seat switch light was always off). Oil pressure light blinked few times and turned off. I think that is also by default

4. Tractor was out of gas when I bought it so I stupidly put some gas from gas canister which might have had some rain water mixed. But it started okay so I didn't think of it much

5. Mowed the lawn 3 times since. Still would struggle to start (cranking quite few times) but once started would work fine

6. After few days of of hard rain (tractor stayed under cover), I tried to start it again and that time it did not start at all. No crank. I forgot to disconnect the battery during rainy days so I thought battery was dead. Put brand new battery, and no crank. I thought maybe that burnt wires are touching each other and shorting and moved the whole connectors back and forth a bit (probably that was a very bad idea and probably did actually created short circuit). 

7. Afterwards, only dash light works is seat switch on. It cranks now but no start. Battery connector is smoking now.

8. Decided it must be the melted wires which caused all the issues and cut burnt parts and connected all back together

9. Checked fuses. Once fuse was completely melted and broken in half. Replaced it with new one.

10. Tried to start. Same as before. Only dash light works is seat switch on. It cranks now but no start. Battery connector is smoking after few tries of crank. This is where I am now.

I will follow your direction and check wiring around the engine for short circuits and frayed insulation. Ignition switch might have died like you said. Also since it's cranking maybe I should try to spray some starter fluid and see. 

My question is, did I manage to fray dash lights? Why there is no dash lights anymore(other than seat switch light)? If seat switch is really on, engine would not even crank right? I feel like dash light is reversed somehow, everything should be on is off and seat switch should be off is on. Also forgot to add, none of the gauges are working too. Fuel, battery etc. 

Edited May 11, 2021 by Sod
clarification on 3. more clarification.

[Handy Don 12,232]

At this point, given your sequence of events, your task is to identify the parts of the electrical system you can trust and work from there. Attempting to start with starter fluid is, to my mind, a waste of time right now and even if it ran, it could cause further damage. As well, the dash lights and gauges are not your immediate problem. They are only indicators, not critical to the operation--in other words, the tractor can run if NONE of them are working as long as the underlying essential circuitry is functioning.

 

The fact that it ran recently is somewhat heartening, but given the fried wires and use of poor fuel, not really all that useful.

 

There won't be any shortcuts to solving this. It'll likely take several hours of work to track down and fix whatever is broken. The 520-H is a great and powerful machine but it is likewise not a simple one. And if it turns out that parts were damaged, it could cost you some money. Sorry for being blunt, but that's where you are.

 

In an earlier post, @lynnmor pointed you to the demystification guide. That is the correct place to start. Have you downloaded and studied that? Do you have the tools needed to do the work--Volt-Ohm Meter, alligator clip jumper wires, etc.? Are you able to follow and perform its steps? If not, you will have to seek local assistance that can. 

 

That's just electrical. Your fuel system may also be compromised from water, rust, and questionable fuel. Ideally, you'd drain any remaining fuel completely, check the state of the fuel lines and filter (replacing as needed), and check that there is no dirt in the fuel tank. It may even be necessary to do a full cleaning on the carburetor.

 

 

[Sod 9]

Update: I fixed it!

However, I think you all may get a kick out of it. After cleaning/fixing the melted wires, dash had only one light on - seat switch(which should be off). It cranked but no start. I was reading the demystification guide, reading your suggestions and trying to figure out what go wrong. Then I noticed that whenever I turn the key to ON, fuel gauge arrow would move downward, way below zero. Then it hit me, everything is reversed, lights, gauges. So I check the battery connecters (RED and GREEN in my case), well I connected them wrong way. Connected the battery correctly, tractor started right up no problem and just mowed the lawn. Happily surprised wrong connection didn't cause any havoc. I should have put some pictures with battery when I was trying to fix the issue, then you guys would have noticed right away. I am pretty embarrassed but also find it hilarious

Thank you very much for all your comments and suggestions. 


@lynnmor, @Handy Don, @gwest_ca, @tom2p, @peter lena, @953 nut, @squonk, @Ed Kennell

Edited May 11, 2021 by Sod
grammar, extra info

[peter lena 8,627]

SOD ,  glad you found it , get used to problems hiding in plane sight , especially when you are up to your eyeballs in issues . now that you have a gain / victory , might be a good time to give it a  mystery oil rub down , easily done ,and the clean looking shine will inspire you for your work. good work , pete 

[Handy Don 12,232]

Shakespeare said it nicely..."All's well that ends well"

Congrats and enjoy.

Now go back and put good connectors on those splices!

(FWIW, I've become a fan of the "solder heat shrink connectors". They do a good electrical/mechanical link and the heat shrink seals out moisture and dust. I use a heat gun at about 600º to close them up.)

Edited May 11, 2021 by Handy Don

[gwest_ca-(File Mod) 11,045]

Your tractor's model number should be 73502 with a serial number between 6900001-6999999.

 

[ERBSHORSE62 10]

Hey SOD,

                     I was just reviewing your Electrical issues and I noticed the COOL LOOKING Foot Control on your 520H.     Do you know where that design came from?    That looks really professional and compact design.  I have a couple 520H's and considered trying to add Foot Controls to at least one of them .  I like the looks of yours.  Do you have any information on it that you could share.   Thanks,  ERBSHORSE. 

[peter lena 8,627]

@Sod  done a number of , frayed dried cracked wires , have regularly used these , to solve the issue ,https://www.amazon.com/KAIWEETS-Electrical-Alligator-Connection-Experiment/dp/B07SB14WPZ/ref=asc_df_B07SB14WPZ?  and retain my sanity . have also replace those connections with OREGON brand connections , reroute wiring runs , eliminate tight bends , cable wrap all wires , and support and separate existing problems. dielectric grease at all connections ,increase grounding to frame area , from battery ground point , and include dash grounding , and tye in headlights  . check as you go and verify gains . good luck with it , pete