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Onan Ignition Module testing - off the engine

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A little time saver to confirm an Onan ignition module is functional prior to installing it, reassembling the engine and keeping your fingers crossed.

The diagram below shows how to wire up a standard tail lamp assembly and a few alligator clips to complete the testing. All the wiring and testing can be accomplished on the bench.

One Caution - DO NOT TOUCH THE BLACK MODULE LEAD TO 12 VOLT POWER AT ANY TIME. IF NO LOAD (lamp or ign coil) IS PRESENT IN THIS LEAD THE MODULE WILL BE DESTROYED.

Onanignitiontroubleshootignmodofftractor_zps98e2388e.gif

The modules I have tested so far power have all powered up with the tail light on. When the trigger ring is rotated near the "nose" of the module, one of the two magnets embedded in the trigger ring will turn off the lamp and continued rotation of the ring will pass the second magnet over the "nose" and once again turn on the lamp.

An ignition coil puts about a 3 - 4 amp load on the ignition module. A standard automotive tail light will also put the module under approximately the same load and provide a good simulation of the ignition coil load.

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Chuck,

as usual, you explain everything in a no brainer way for us less knowledge d folks. While the Onan engine repair manual goes over a step by step diagnostic testing, you provide a legible, color diagram that is so easy to understand. perhaps you could re write the Onan repair book in your "SOI esque" style?

you could name it "SOI's Onan Electrical Repair Guide or How I stopped pulling my hair out every time my 520 doesn't start and learned to love my P220G" :D :text-thankyouyellow:

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That is simple, I have a few of them I can test and mark good, or throw in the trash now.

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So, in the absence of a spare rotor, can I simply wave a magnetic by the ignition module and get the same result?

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So, in the absence of a spare rotor, can I simply wave a magnetic by the ignition module and get the same result?

Yes. I don't know (yet) which is the North or South pole on the rotor, but the on and off transition of the ignition module is triggered by a north pole and then again by a south pole.

So yes, just flip the magnet over end for end. A bar shaped magnet would be best and easiest to use.

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A little time saver to confirm an Onan ignition module is functional prior to installing it, reassembling the engine and keeping your fingers crossed.

The diagram below shows how to wire up a standard tail lamp assembly and a few alligator clips to complete the testing. All the wiring and testing can be accomplished on the bench.

One Caution - DO NOT TOUCH THE BLACK MODULE LEAD TO 12 VOLT POWER AT ANY TIME. IF NO LOAD (lamp or ign coil) IS PRESENT IN THIS LEAD THE MODULE WILL BE DESTROYED.

Onanignitiontroubleshootignmodofftractor

The modules I have tested so far power have all powered up with the tail light on. When the trigger ring is rotated near the "nose" of the module, one of the two magnets embedded in the trigger ring will turn off the lamp and continued rotation of the ring will pass the second magnet over the "nose" and once again turn on the lamp.

An ignition coil puts about a 3 - 4 amp load on the ignition module. A standard automotive tail light will also put the module under approximately the same load and provide a good simulation of the ignition coil load.

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Hi again! I bought a new module and tried the light and battery thing on it like I did the old one and it still did not light up I even printed the diagram the squirrel had on and mad sure I hooked it all up the right way and the light still did not come on? Is there something I'm missing or is it just me? I want to put my wheel horse back together should I just put the new one in and hope for the best ?

Thank you guys for all your help

Do I need to use a magnet to do this test or is this just an example of how the system works?

 

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Make sure you are using a single filament bulb and socket. Any good magnet should work. Pass one pole and then the other.

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I used a single filament bulb , but not quit sure what to do with the magnet? What do your mean by pole ? those round spots on the plastic ? do I hold the ground wire from the battery on also at the same time?  I put the new module in and put the tractor back together. It fired right up!  I ran it for a few minuets and shut it off and restarted it a couple of more time and it ran good . Then I went on to something else and when I came back to it it would not start again !! have sparke this time so now something else must be going on.

 Tomorrow's another day .

         Thank you

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Went out this morning and it started right up again ? I ran it for  some time and it restarted but my fuel guage and volt meter werent showing ? I moved the wiring harness around and they started working. My volt meter was reading completly over in the high side like it has done for some time now. But when I put my meter on the stator connections I have no reading ? I dont have the deck back on but I put the PTO on just to try it and when I did the tractor wants to die? I pulled the seat off and the back fender and cleaned all of the switches and checked them all with my meter and looked over all of the wiring and everything looked good and checked out. That is the first time I have ever taken the seat and the fenders off in 28 years. WOW was it dirty under there. Dont know why it is trying to quit when I put The PTO on? The switch and the contacts to it are all clean and look good.

 But at least its starting for now .  Any ideas would be helpful :eusa-think:

 

 I checked all of the saftey switches, seat , break, motion lever ext.  they all are clean and working. I cleand all ground wires. See no breaks or worn spots on anything in the harness

Edited by Jess

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Went out this morning and it started right up again ? I ran it for  some time and it restarted but my fuel guage and volt meter werent showing ? I moved the wiring harness around and they started working. My volt meter was reading completly over in the high side like it has done for some time now. But when I put my meter on the stator connections I have no reading ? I dont have the deck back on but I put the PTO on just to try it and when I did the tractor wants to die? I pulled the seat off and the back fender and cleaned all of the switches and checked them all with my meter and looked over all of the wiring and everything looked good and checked out. That is the first time I have ever taken the seat and the fenders off in 28 years. WOW was it dirty under there. Dont know why it is trying to quit when I put The PTO on? The switch and the contacts to it are all clean and look good.

 But at least its starting for now .  Any ideas would be helpful :eusa-think:

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Have you checked the nine pin connector? it gets dirty and corroded and after so many yers of use can cause all kinds of problems.

As you can see from this image, I have an arrow pointing to the connector. Most of the electronics pass through this connection. It is white and is easily located.

post-2564-0-26231700-1411398766_thumb.jp

I have a suggestion for you that may save you untold problems in the future but will entail additional work now. Or you might want to wait till the mowing season is over. Remove the engine and take off all the tins on it. I will bet you will find an enormous amount of dirt, crud combined with oil behind the rear engine shroud where the filter is. after power washing this completely, take off the heads and adjust the valves. Onan recommends Valve adjustment and de-carbon be done every 500 hours. If you don't want to do the valves, at least clean the crud out. This is an important step to follow because it constricts the flow of air around the engine and cause the rear cylinder to overheat. Also if after changing the oil the rubber ring that inserts on the outside of the filter has been lost or simply not replaced, get a new on and put it on. This acts as a cover to prevent the flow of air from escaping around the filter so that it is directed where it can do the most good.

Many folks do not like the Onan. It takes a bad hit because of the rear cylinder. But if they simply follow maintenance directions these engines will last forever. The problem is that Wheel Horse installs them sideways and this invites the heating problem because of the close quarters in the Wheel Horse application.

Proper maintenance is the key to longevity. If it were me I would do the valves and de-carbon as it is easily done by anyone with a small amount of tools.

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Have you checked the nine pin connector? it gets dirty and corroded and after so many yers of use can cause all kinds of problems.

As you can see from this image, I have an arrow pointing to the connector. Most of the electronics pass through this connection. It is white and is easily located.

attachicon.gifPARTS CATALOG_Page_46.jpg

I have a suggestion for you that may save you untold problems in the future but will entail additional work now. Or you might want to wait till the mowing season is over. Remove the engine and take off all the tins on it. I will bet you will find an enormous amount of dirt, crud combined with oil behind the rear engine shroud where the filter is. after power washing this completely, take off the heads and adjust the valves. Onan recommends Valve adjustment and de-carbon be done every 500 hours. If you don't want to do the valves, at least clean the crud out. This is an important step to follow because it constricts the flow of air around the engine and cause the rear cylinder to overheat. Also if after changing the oil the rubber ring that inserts on the outside of the filter has been lost or simply not replaced, get a new on and put it on. This acts as a cover to prevent the flow of air from escaping around the filter so that it is directed where it can do the most good.

Many folks do not like the Onan. It takes a bad hit because of the rear cylinder. But if they simply follow maintenance directions these engines will last forever. The problem is that Wheel Horse installs them sideways and this invites the heating problem because of the close quarters in the Wheel Horse application.

Proper maintenance is the key to longevity. If it were me I would do the valves and de-carbon as it is easily done by anyone with a small amount of tools.

I went out and bought my 3rd wheel horse this summer only because both of my machines went down and I couldnt get any help in fixing them . My 520 was running untill I got the bright idea of switching coils! Thank you for the schematic and help! I will keep it with my owners manual! and look for the white connector. I took that main connector apart and cleaned it a bit and put some of the eclectic conductor gel on it before I put it back together. Maybe that messed it up. I have always performed regular maintenance on it and have pressure washed it off many times over the years and blow everything out regularly. I think that is why it has lasted all these years. I paid around $5,000 for it with the deck and power vacuum set up back in 1986 and always try and take care of my equipment as best I know how. I think my 520H and 518H with these onan motors are great and life time machines.

Thank you again for your help and I will go and spend some more hrs on it today and see if I can finally get it all back together, deck and all

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Have you checked the nine pin connector? it gets dirty and corroded and after so many yers of use can cause all kinds of problems.

As you can see from this image, I have an arrow pointing to the connector. Most of the electronics pass through this connection. It is white and is easily located.

attachicon.gifPARTS CATALOG_Page_46.jpg

I have a suggestion for you that may save you untold problems in the future but will entail additional work now. Or you might want to wait till the mowing season is over. Remove the engine and take off all the tins on it. I will bet you will find an enormous amount of dirt, crud combined with oil behind the rear engine shroud where the filter is. after power washing this completely, take off the heads and adjust the valves. Onan recommends Valve adjustment and de-carbon be done every 500 hours. If you don't want to do the valves, at least clean the crud out. This is an important step to follow because it constricts the flow of air around the engine and cause the rear cylinder to overheat. Also if after changing the oil the rubber ring that inserts on the outside of the filter has been lost or simply not replaced, get a new on and put it on. This acts as a cover to prevent the flow of air from escaping around the filter so that it is directed where it can do the most good.

Many folks do not like the Onan. It takes a bad hit because of the rear cylinder. But if they simply follow maintenance directions these engines will last forever. The problem is that Wheel Horse installs them sideways and this invites the heating problem because of the close quarters in the Wheel Horse application.

Proper maintenance is the key to longevity. If it were me I would do the valves and de-carbon as it is easily done by anyone with a small amount of tools.

I went back over all of the wires and cleaned them again just to make sure and all still look good I discontcted  that white  main harness  again also but no luck . Tractor still wants to die when I put the PTO on ?

I will have to try and trace out all of the wires and see if I can tell what is going on . I use this machine a lot in the fall with picking up the leaves an all.
But not very good at wiring and you can tell from my previous post

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The first thing I do when I get a tractor and I have got a lot of the, is to go to Toro and using the model and serial number, down load all the books and put them in a file. I am anal about documentation and I even print them out. I refill my own ink cartridges for the printer I use for this purpose so the cost is minimal.

Another thing I do is take a lot of photographs of anything I am about to dismantle and repeat this on each thing I take off the tractor.

As far as help is concerned, you now have thousands of buddies just waiting to pitch in with advice. Just remember that we all make a mistake now and then so if someone steers you in the wrong direction, have patience because someone else will come along and gently correct it.

By the was Jess I notice that you have not become a Supporter yet. You might want to do that so that we can keep this site up and rolling along for those who need it. Not a demand just a friendly suggestion.

Now, let's start on those other two Wheel Horses that need fixing.

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The first thing I do when I get a tractor and I have got a lot of the, is to go to Toro and using the model and serial number, down load all the books and put them in a file. I am anal about documentation and I even print them out. I refill my own ink cartridges for the printer I use for this purpose so the cost is minimal.

Another thing I do is take a lot of photographs of anything I am about to dismantle and repeat this on each thing I take off the tractor.

As far as help is concerned, you now have thousands of buddies just waiting to pitch in with advice. Just remember that we all make a mistake now and then so if someone steers you in the wrong direction, have patience because someone else will come along and gently correct it.

By the was Jess I notice that you have not become a Supporter yet. You might want to do that so that we can keep this site up and rolling along for those who need it. Not a demand just a friendly suggestion.

Now, let's start on those other two Wheel Horses that need fixing.

Thank you , I don’t see anything else to check with the wires . I may have to step away for a while and come back at it with a fresh mine (NOT MINE)
I don’t see how to become a supporter? I'm not very tech savvy . I have tried to download some manuals from Toro but cant seem to find them ?
I will keep on checking .
Thanks for your help
 
Jess

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i think you are loosing 12+ volts to the coil when you operate the pto. check the wiring at the pto microswitches to make sure that is wired correctly, all terminals are making contact and the switches aren't damaged from the lever...... 

with it running, check the yellow wire at the coil (+) for 12 volts. operate the pto lever, check again. if you don't have 12v at the coil (+) when the lever is on while engine is running problem is in the pto wiring/switch or kill relay somewhere. if you can get enough access to the pto switches you can test them while the harness is still plugged in. the pto switch(es) work in a way that ignition power will be cut if the engine isn't running, so you can't start it with the pto engaged. but with the engine running you should be able to engage and disengage the pto without loosing power.

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i think you are loosing 12+ volts to the coil when you operate the pto. check the wiring at the pto microswitches to make sure that is wired correctly, all terminals are making contact and the switches aren't damaged from the lever...... 

with it running, check the yellow wire at the coil (+) for 12 volts. operate the pto lever, check again. if you don't have 12v at the coil (+) when the lever is on while engine is running problem is in the pto wiring/switch or kill relay somewhere. if you can get enough access to the pto switches you can test them while the harness is still plugged in. the pto switch(es) work in a way that ignition power will be cut if the engine isn't running, so you can't start it with the pto engaged. but with the engine running you should be able to engage and disengage the pto without loosing power.

I took all of the micro switches out and cleaned them and checked them with my meter to see if the were working properly and they were. The wiring to them are just plug in so I didn’t get them mixed up as they only go one way. When I have the tractor running I cant engage the PTO as it Kills it. I did do a couple of other things while I was working on it. The terminal at the key switch were coming un riveted so I installed a new Wheel Horse key switch and it just plugged right in and I checked to make sure the switch was right. Then my starter solenoid was acting up so I installed a new starter solenoid and that all looks good so I now have no problem with it cranking. It acts like when I engage the PTO it is just killing the machine.
Thank you for your help and time. Much appreciated

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Hook up a volt meter from the Battery negative to the positive side of the coil, With the engine running you should see 12 volts. Now engage the PTO. Watch the meter. If the voltage drops to zero, you have something electrical causing the problem. Let us know what happens and then we can go further.

Edited by km3h

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Hook up a volt meter from the Battery negative to the positive side of the coil, With the engine running you should see 12 volts. Now engage the PTO. Watch the meter. If the voltage drops to zero, you have something electrical causing the problem. Let us know what happens and then we can go further.

 

 

Hook up a volt meter from the Battery negative to the positive side of the coil, With the engine running you should see 12 volts. Now engage the PTO. Watch the meter. If the voltage drops to zero, you have something electrical causing the problem. Let us know what happens and then we can go further.

 did just that I put my meter on the bat neg post and check the voltage to the positive side of the coil . With the machine running I had aprox 13 plus volts on the neg side of the coil I also had voltage aprox 11 volts ? I found a balk wire going to that white terminal connector and it had a spot under the motor that had part of the insulation worn off from rubbing on something and was intermittently grounding out ? When I repaired it the machine started to run normal ? I could engage the PTO and the motor keeps running now ( Great) progress.

My volt gauge still reads all the way barred on the high side but when I put my meter on the studs where the wires are hooked up to it I'm getting almost 14 Volts , which I think would be normal changing? Maybe my gauge is no good? I also cant get my lights to come on? The switch on the dash checks out OK But no power to the lights where they hook up ? No back lights either? But at least the tractor seems to be running OK.
Thank you for your time
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The lighting circuit is fairly simple to check. Looking at the schematic you will see that a pink wire runs from the A of the key switch to a 15 Amp fuse in the fuse block. From there it carries voltage to the toggle switch on the dash. If you are getting 12 volts to the switch, you must have a faulty connection or no ground at the lights. No voltage at the switch would indicate a blown 15 Amp fuse.  

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The lighting circuit is fairly simple to check. Looking at the schematic you will see that a pink wire runs from the A of the key switch to a 15 Amp fuse in the fuse block. From there it carries voltage to the toggle switch on the dash. If you are getting 12 volts to the switch, you must have a faulty connection or no ground at the lights. No voltage at the switch would indicate a blown 15 Amp fuse.  

 

The lighting circuit is fairly simple to check. Looking at the schematic you will see that a pink wire runs from the A of the key switch to a 15 Amp fuse in the fuse block. From there it carries voltage to the toggle switch on the dash. If you are getting 12 volts to the switch, you must have a faulty connection or no ground at the lights. No voltage at the switch would indicate a blown 15 Amp fuse.  

The toggle switch to the lights was intermittently working. I took took it apart and cleaned the contact , spring and the rest of the switch, Now have lights again! Cleaned and painted the bottom on the deck , sharpened & balanced the blades and reinstalled deck ! Washed and waxed tractor ! Runs and cuts like a new machine again. Haven't used this machine since the beginning of spring when it died . I love the Onan motors ! Need to find a new seat cover :)
I now have 3 running horses thank you for your time and help! :woohoo:
 
Jess

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It is always a pleasure to help a fellow Wheel Horse enthusiast.

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It is always a pleasure to help a fellow Wheel Horse enthusiast.

 

It is always a pleasure to help a fellow Wheel Horse enthusiast.

Well I guess I spoke to soon! It ran great for about 20min when I was testing it out and the it started to loose power and backfire ! It died again. Back to one dead horse. It would not restart.

It was getting gas and spark. I let it sit for a while and then it started right up and ran great for about 15 min and died again. when it dies it wont restart with out letting it sit for about 20 min or so. I pulled the carb off and took it apart and cleaned everything and reinstalled it thinking maybe a float thing. It started right up again and ran great for about 5 min and back to the same thing?
Maybe electrical or some kind of timing thing? Maybe the ignition coil ?
Edited by Jess

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If you are getting spark when this happens then the only other problem  must fuel. I am assuming that the air intake is not blocked. Check the gas cap. It has a vent hole and may b e clogged. This forces the fuel pump to pull against a vacuum. When it stops running pour about a spoon full of gas in the carb. I have a small fuel tank with a cutoff valve and two feet of hose. When I have a problem like that I hook it up and gravity feed it. If it starts then I hook it to the fuel pump and sit the tank down below it.     

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