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Hughes Small Engine

520H no spark...no idea about the wiring

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Hughes Small Engine

Hey there, I'm new here. I just picked up a (mid-late 80s? Guy said he thought it was an '88) 520H, 20hp Onan XSL, with snowblower, cab and deck for cheap money the other night. I've never had a wheel horse before, but I've wanted one for years so when this popped up in the local market place I had to buy it. The guy I bought it from said it didn't have spark. He had some guy do a house call, guy took the old ignition coil with him, brought a new one and never hooked it up. So I got this machine with a new coil but all the wiring is disconnected for the coil. I found the yellow wire to be B+ and found information here that seemed to show the orange and yellow and black condenser wire going to the B+ terminal. So I'm guessing the other black wire coming from the engine harness is for the ground side of the coil? I hooked it up that way and still don't have any spark. I haven't dove into it any more than that. I did test the new coils resistances on the primary and secondary sides and they are within range (as I expected). I'll add some pictures below. Any ideas or do I have the coil hooked up wrong? New battery, engine cranks over fine and the lights work. Tachometer doesn't but I don't know whether that's because of the coil not being hooked up correctly or if the tach is bad. Any help is appreciated! Thanks! 

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Edited by Hughes Small Engine

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1995 520H+96+97

The terminals on the coil are different diameters. If the terminals on the orange and black wires(to ignition module) have not been changed, the coil can't be connected wrong. Check your fuses for voltage, and check 9 pin connector. :wh:

 

:text-welcomeconfetti:to :rs:

Edited by 1995 520H+96+97

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Hughes Small Engine
1 minute ago, 1995 520H+96+97 said:

The terminals on the coil are different diameters. If the terminals on the orange and black wires(to ignition module) have not been changed, the coil can't be connected wrong. Check your fuses for voltage, and check 9 pin connector. :wh:

 

:text-welcomeconfetti:to :rs:

I'm not sure if they've been changed or not, but I would assume they have been. So the black wire from the ignition module goes to negative on the coil and the orange goes to positive along with condenser and switched + wires? Should I have voltage at all fuses? What should I be checking for at the 9pin connector? Thanks

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gwest_ca

Welcome to the forum.

Garry

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Hughes Small Engine

I found that schematic earlier. From what I'm looking at it shows the orange and yellow wires to the + coil terminal but doesn't show anything connected on the negative side. I'm assuming the condenser goes to the + terminal as well. I'm assuming that since I have voltage at the yellow wire that all of the wiring from the ignition switch to the coil is good. All the fuses I can see are good as well. Just not sure of the voltage regulator in front of the battery could cause and issue here or if the ignition module under the shroud is bad (that's where the orange and black wires come from I'm assuming?)

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gwest_ca

The condenser goes to the (+) coil terminal in this application.

The Wheel Horse wiring diagram shows just the tractor wiring.

The rest of the wiring is considered part of the engine

Garry

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Hughes Small Engine
3 hours ago, gwest_ca said:

The condenser goes to the (+) coil terminal in this application.

The Wheel Horse wiring diagram shows just the tractor wiring.

The rest of the wiring is considered part of the engine

Garry

Awesome! Thanks I read through the ignition operation section and I'm going to do some of that troubleshooting tomorrow. Explains the ignition system to me a little better. And also affirmed that I have the coil hooked up correctly. I'm guessing it's going to need a new ignition module at this point but I won't know for sure until tomorrow. Does that magnetic pickup ring on the crank behind the flywheel ever go bad or lose its magnetism? 

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lynnmor
1 hour ago, Hughes Small Engine said:

Awesome! Thanks I read through the ignition operation section and I'm going to do some of that troubleshooting tomorrow. Explains the ignition system to me a little better. And also affirmed that I have the coil hooked up correctly. I'm guessing it's going to need a new ignition module at this point but I won't know for sure until tomorrow. Does that magnetic pickup ring on the crank behind the flywheel ever go bad or lose its magnetism? 

The early, black ones did fail, the later gray parts were reliable.  I don’t know the year that changed.

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Hughes Small Engine

So I did the test this morning - placed DMM + lead on - coil terminal and DMM - lead on engine ground. Key on and rotated engine to see if it would switch between B+ and 1-1.5v. DMM shows 12v all the time never switches. So by that reasoning I'm assuming the ignition module or pickup under the flywheel is bad. Right? 

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lynnmor
36 minutes ago, Hughes Small Engine said:

So I did the test this morning - placed DMM + lead on - coil terminal and DMM - lead on engine ground. Key on and rotated engine to see if it would switch between B+ and 1-1.5v. DMM shows 12v all the time never switches. So by that reasoning I'm assuming the ignition module or pickup under the flywheel is bad. Right? 

Sounds like it is spent.  Look for bad wiring from coil to module before ordering parts.

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Hughes Small Engine
Just now, lynnmor said:

Sounds like it is spent.  Look for bad wiring from coil to module before ordering parts.

I'll pull the flywheel off and take a look. My only uncertainty is that all the other videos and tests I've found show that when the ignition module is bad that it'll only show < 1v and not switch to 12v. I however show 12v all the time on my DMM which is why I was wondering if it could still be a bad ignition module or if there was something else wrong. 

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Hughes Small Engine

One other thing I'm not sure about that could be causing an issue here - if one of the safety switches is bad or if the low oil switch is bad, would the engine still crank over but not create spark or will those switches prevent the engine from even turning over? My seat safety switch is finicky (light on the dash flickers on and off just banging around under the seat). The parking brake is set though so I would assume it wouldn't matter. My engine cranks over just fine. Just don't know if I should bother jumping all the safety switches or not. 

 

Also, does anyone know what the ohm specs are for the ignition module? I get 50-60 ohms between the orange and black wires from the module and I get 1500 ohms between the black wire and ground. Not sure if that black wire should be a direct ground or not (guessing less than 5 ohms?) 

Edited by Hughes Small Engine

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gwest_ca

The only models to have the low oil switch are those with a Kohler single cylinder engine and on those it interrupts the starter circuit if the oil level is low..

Check to make sure the ignition (+) on the coil has battery voltage in both run and start key positions. If so the safety switches are OK. Have seen ignition switches fail with one or the other switch position.

Have no experience with the rest of it.

 

Garry

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lynnmor

You should jump the seat switch if it is acting up.  The previous manuals will help you troubleshoot the problem.  I've not checked ohms on a module, it is simply a solid state magnetic switch that turns on and off as a magnet passes it, but it may do nothing without voltage applied..  The Onan test for voltage changes as the engine is turned is all you need to do, just be sure that you have the 12 volts working at the coil.

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Hughes Small Engine
1 hour ago, lynnmor said:

You should jump the seat switch if it is acting up.  The previous manuals will help you troubleshoot the problem.  I've not checked ohms on a module, it is simply a solid state magnetic switch that turns on and off as a magnet passes it, but it may do nothing without voltage applied..  The Onan test for voltage changes as the engine is turned is all you need to do, just be sure that you have the 12 volts working at the coil.

Alright I'll jump the seat switch. I know the Onan test but it isn't staying stagnant at 0-1v like others I've seen when the module is bad, it's showing 12v all the time. I have 12v on the positive coil terminal and the negative coil terminal. And I do have B+ from the yellow wire to the coil... obviously. 

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RubyCon1

 

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OllieThePom
On 11/25/2019 at 2:28 AM, Hughes Small Engine said:

I'll pull the flywheel off and take a look. My only uncertainty is that all the other videos and tests I've found show that when the ignition module is bad that it'll only show < 1v and not switch to 12v. I however show 12v all the time on my DMM which is why I was wondering if it could still be a bad ignition module or if there was something else wrong. 

Hi Hugh, do you have links for the videos you've found? are they on youtube? Im having trouble diagnosing if my ignition module is infact at fault. 

 

Thanks, Ollie

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Hughes Small Engine
14 hours ago, OllieThePom said:

Hi Hugh, do you have links for the videos you've found? are they on youtube? Im having trouble diagnosing if my ignition module is infact at fault. 

 

Thanks, Ollie

Hey Ollie, yeah I found them all on YouTube. Just type in 520H ignition testing or Onan 20hp Performer ignition testing and you'll find them. Pretty much people just running through the same tests as the demystifying manual shows. My issue is everyone else who has a bad ignition module is showing 0v on the black wire from the module not switch to 12v every rotation but I'm showing 12v all the time not switching on engine rotation. 

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Hughes Small Engine

Well, I ended up deciding on a gut feeling that the ignition module was shorted internally since I had 12v constantly coming from the black wire off of the module. I ordered a new module and pickup ring for $160. Put them in last night and hooked everything back up...I was right! Great spark now. Now it's onto replacing the fuel lines and figuring out why the gauges don't work (apart from engine vacuum.) It seems the gauges all get switched power from the ignition switch right? Are these switches known for going bad? It cranks and starts fine but none of the gauges are getting 12v with the key switched on. I tested the wiring from the switch plug to the gauges and the battery + and that's all good. So I'm guessing the switch contacts are connected the B+ to switched power wire when the key is turned on. 

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lynnmor

Wheel Horse used the same cheap switches as most of the consumer grade tractors, so yes they fail all too frequently.  You can buy them at NAPA and many places, just don't get the real cheap junk from China.  It is getting impossible to judge quality, so even NAPA might be selling the low end stuff now.

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Hughes Small Engine
1 hour ago, lynnmor said:

Wheel Horse used the same cheap switches as most of the consumer grade tractors, so yes they fail all too frequently.  You can buy them at NAPA and many places, just don't get the real cheap junk from China.  It is getting impossible to judge quality, so even NAPA might be selling the low end stuff now.

Alright that's what I was thinking. It looked the same as all those other basic Indak switches. I was at Napa today and they had several options but I forgot to take my old one with me to match up. I'll have to do that tomorrow. (Closest Napa is a 30 minute drive)

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gwest_ca

This is the switch you need. Click on the picture for more info.

Garry

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Hughes Small Engine
On 12/7/2019 at 8:12 PM, gwest_ca said:

This is the switch you need. Click on the picture for more info.

Garry

Thanks for that! I went to my Napa and found the right switch. Installed it but that wasn't it although I was able to find a potential future issue with the ignition switch wiring which I was able to fix. Anyway I ended up doing a little more wire investigation and isolated the part of the switched power circuit that had high resistance. The fuse holder for the accessories circuit was corroded and causing 650 ohms of resistance. Cleaned everything up but only got it down to about 18 ohms. So I went out and got a fuse holder. I'm going to get a fuse block though and wire that I'm eventually. Getting into this today really made me want to just rewire the tractor myself...but at the same time I really don't know want to deal with rewiring everything. 

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cleat

Best thing I did for my 520's is to pull the entire wire harness out then clean it and lay it out on the bench and go through it.

I remove all wiring that I don't need and that cleans it up a bit.

 

Then check and replace any connector that does not look really good.

 

I replace all fuse holders with sealed units and replace the 9 pin with a sealed unit.

 

Rewire charge power to go directly to the starter via an inline 30A fuse to get that current out of the 9 pin.

 

Never an issue after that.

  • Excellent 1

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Jerry.Guzzi

I'd like to wire my 1997 Classic  520 H like an older model. I don't need a tach, or gas gauge or head heat censers. Right now though, I'm trying to find wiring for my 417a I changed to 520H.

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