520h coil question

[zeedubbya 18]

I have noticed that my 520h seems to be "missing" just a bit at all rpm ranges. It's not a lot just an annoying little cut out kind of? I checked everything out with a multimeter last night and the only thing that wasn't in line with what the onan manual stated was primary coil resistance. The manual recommends it be between 2.9-3.6 ohms and it was registering 3.9? Does this indicate a bad coil? Typically I would think that .3 of an ohm would be inconsequential however the accepted range is only .7 of an ohm? The secondary resistance is fine registering at 18,400? Any thoughts would be appreciated. Thanks!

[Save Old Iron 1,563]

If you are using a digital meter, hold both probes together when on the low ohms scale, You will probably find the meter registers some "residual" resistance most likely in the meter leads or where the meter leads connect to the meter case. Lets say you see .4 residual ohms - you can then subtract that residual reading from the overall reading to get the true reading of the primary coil.

No idea if this possible increase in primary resistance means on oncoming failure. There are so many other factors at play here that could cause rough / missing ignition. Condenser, ignition module, valve adjustment, valve seats, carbon buildup in heads, spark plug wires, spark plugs, spark energy escaping from split boots or wires, carb issues, etc - all possible players here.

[zeedubbya 18]

You were right as always!! .4 residual Ohms on the meter so it appears coil is good then.

[Save Old Iron 1,563]

Power to the ignition system could be intermittently dropping out. A combination of rough lawn, lightweight driver and a mis-adjusted or corroded seat switch could make for a difficult to diagnose intermittent cutout of ignition. The seat switch thinks you are leaving the seat for a fraction of a second then you are back on again and the engine recovers.

[varosd 1,185]

Power to the ignition system could be intermittently dropping out. A combination of rough lawn, lightweight driver and a mis-adjusted or corroded seat switch could make for a difficult to diagnose intermittent cutout of ignition. The seat switch thinks you are leaving the seat for a fraction of a second then you are back on again and the engine recovers.

"lightweight driver" Hey! I'm at least 140 pounds....soaking wet!

Chuck, your avatar is "Angry Beatnik Birds" now instead of studious squirrels? :laughing-rollingyellow:

[Save Old Iron 1,563]

Chuck, your avatar is "Angry Beatnik Birds" now instead of studious squirrels?

Just been hanging with the Clydes and Squares on the Cub sites, diggin' the coolness of going to "Splitsville" with "far out" tolerances in my 104 transaxle.

[zeedubbya 18]

Ok update to what has now become a bigger problem it seems. Havent ran it for two weeks because no rain=no grass. The 520h is now shutting down intermittently with no light telling me why? All I have to do is fire it back up and it will keep going until at some point it stops again. One time it did it twice in a row and it apparently didnt have enough juice to turn the starter--i could hear the starter clicking a bit i still had to jump it, but then it ran fine. Very very annoying. So is it a safety switch like Chuck mentioned before, is something possibly going wrong in the electrical system, or is my battery shot? I can say that the wiring harness in this tractor looks like a 12 year old re-wired it, even though it was "professionally done" at a repair shop according to the records the PO kept. I really need to take a picture and post it on here so I can get some advice on how to put it back right. Thanks for any input!

[Save Old Iron 1,563]

One time it did it twice in a row and it apparently didnt have enough juice to turn the starter--i could hear the starter clicking a bit i still had to jump it, but then it ran fine. Very very annoying. So is it a safety switch like Chuck mentioned before, is something possibly going wrong in the electrical system, or is my battery shot?

I'm a big believer in battery testing as a first step for slow crank issues - especially on the highly "electronic" circuits in the 520's. Too many random sparks from battery jumps can cause failures in the ignition modules and dash displays.

The best indicator of battery wellness is a specific gravity test on all cells. If you have a no maintenance battery, then a load test is the next best method. If you don't have a load tester - shame on you.

This is a short video of a load tester hooked to a battery that measures perfectly fine @ 12.6 volts with a voltmeter. Notice how quickly the voltage drops to less than 9 volts under a 50 amp load.

Measure the voltage directly across the battery terminals when you are experienceing a slow crank. If the battery voltage is dipping down below 10 volts, your battery may be weak. If you can start the engine right up with a jump, your wiring is probably ok.

[zeedubbya 18]

I guess I'm not gonna get my diploma from SOI U because I don't have a load tester . Battery wouldnt start 520h this morning when I went out to do some troubleshooting. Multimeter says 12.1 volts at battery but when I tried to start it it jumps down to about 6 volts. So I think battery is done. Going to buy a new one today. However I got it started so I could troubleshoot it and did a lot of the checks you recommended on another post. Regulator seems fine across all tests except for the b+ DC voltage check. It sends the correct voltage to the B+ but it's present even with the key in the off position. It actually drops a small amount with key in the run position? Also for some reason my tachometer has voltage to it even in the off position? The tach doesnt even work? Does this indicate a bad ignition switch? Would I just waste my money on another battery if I don't fix this issue? Also I read another SOI post that said if the wires on the stator and the tach were on the RR wrong it wouldn't work? Is there any harm in swapping them and seeing if the tach works? I really appreciate the advice--Chuck you are really amazing at solving problems and explaining them--we are fortunate to have you here. Now do I get an SOI U diploma? Ha ha!

[Save Old Iron 1,563]

I guess I'm not gonna get my diploma from SOI U because I don't have a load tester .

Not true. The alternate method of using a voltmeter across the battery proved the battery does need replacement. I'll have my crack new recruits in the graphics department send up a diploma. Well deserved.

Regulator seems fine across all tests except for the b+ DC voltage check. It sends the correct voltage to the B+ but it's present even with the key in the off position. Also for some reason my tachometer has voltage to it even in the off position? The tach doesn't even work? Does this indicate a bad ignition switch?

Some fine troubleshooting there Zee.

Let me pull out my 520 wiring diagrams tonight and have a look. Initial thoughts are not a bad ignition switch but possible wiring issues. There is something different about the 520's in that they "R" terminal is not used on the ignition switch. My recollection is the battery is wired directly to the regulator thru a 30 amp fuse.

Would I just waste my money on another battery if I don't fix this issue? Also I read another SOI post that said if the wires on the stator and the tach were on the RR wrong it wouldn't work? Is there any harm in swapping them and seeing if the tach works?

A new battery is the best assurance for the long term health of the 520. I think of all the models out there, the 520 has the most to lose "electronically" (gauges, dash indicators, ignition modules) by the stresses of continued battery jumping. This is most likely a simple issue. We will find it.

Yes, the tach signal comes off the rectifier regulator assy. If we look back thru some recent posts, the correct terminal of the RR unit may be identified. If I remember correctly, the flat electrical connector was just flipped end to end and the tach began to work just fine. This would make sense as the tach sensor connector would then be in contact with the opposite AC terminal on the RR unit.

I'll make a quick check but I am certain two of the three terminals on an "Onan" style RR unit are electrically connected together. This hard connection was proven to be the case in a previous C series RR unit I autopsied a few years back.

If the Tach sensor wire is connected to the AC terminal common to the B+ terminal - yes - you would get 12 volts on the Tach gauge (S)ensor terminal. Let me make a few quick resistance checks on Onan RR's tonight and I'll have something for you on Friday.

I really appreciate the advice- Now do I get an SOI U diploma? Ha ha!

I'm very pleased I can put that knowledge to work and consistently help others with not only resolving a problem but to contribute to the understanding of why the problem happened. You gained the confidence of knowing you are spending money that you really do need to spend, not just crossing your fingers in hopes the trip to the auto store might help. You know from troubleshooting (not guessing) the battery is the issue.

[zeedubbya 18]

It seems the battery was an issue, however I still have major concerns about the wiring on this machine. It really looks like a hack job to me. I'll get a picture on here soon enough. It looks like someone maybe took both stator leads and put them together in some sort of Blue "two to one" connector? The way the wiring looks is as if the tachometer wire goes to the tach from one A/C terminal on the RR and the other A/c terminal has both stator leads Hooked to it by being joined into one. Also that would explain why when I tried to

Get an A/C reading on the stator from the RR I couldn't but I could through the stator leads. I am learning as I go, and I really appreciate your help Chuck! That picture of the squirrels working on the diploma Is really really hilarious! I sincerely look forward to your next lesson professor!

[Save Old Iron 1,563]

I am learning as I go

Yeah, me too. I must have looked at the 520 wiring diagram a hundred times in the last few years and it never clicked in my mind the RR unit is not connected to the ignition switch. The "R" terminal on the ignition switch is not used.

So

this is ultimately where we need to end up as far as RR wiring

The B+ terminal and the RIGHT SIDE AC terminal are electrically the same.

Therefore, the AC signal for the tach will come off the LEFT SIDE AC terminal of the RR unit.

For now, I would say just get the wiring correct for the two stator leads into the RR AC terminals and make sure the B+ terminal heads out to the battery via a 30 amp fuse holder. I show a connection directly to the battery but I believe the B+ terminal goes to a fuse holder, then to the stud on the starter relay which leads directly back to the (+) battery terminal.

I would initially leave the grey wire from the tach gauge without a physical connection to the gauge itself. We don't know if the tach works yet but let's just get the charging circuit to work correctly. We can then proceed on to working on the tach circuit.

[zeedubbya 18]

Here is the picture of this messed up wiring. One stator lead goes into the blue connector, the other one gets looped back around with the burnt up piece of material that looks kind of like a heat shrink electrical connection and then goes into the blue connector as well. From there one wire comes from the blue connector and goes into the right A/C side of the RR. The red wire from B+ is correct or so it seems--it goes from the RR to a fuse to the battery. This cannot be a good set up. Am I correct in this assessment? Also to fix it should I just pull that connector off and lengthen the stator leads and put them where they should be? Thanks for the input, I have really learned a lot in this post, and I hope it helps others sometime!

[zeedubbya 18]

Well Just to drop some finality on this post I re-wired the stator leads this evening and everything is charging as it should. 33vac across ac terminals of RR and 14.3 at b+ and battery while running. Also while running my voltmeter reads the 14.3 it's supposed to when it was reading around 11 before. I suppose I can now move on to the tach because it's currently not hooked up per the advice of SOI, the master and teacher. So if you read this SOI ( or anyone else that knows?) should I just go ahead and wire the gray tach wire into the left ac terminal? If so is it ok to wire it up the stator lead wire a little ways, or does it have to have a direct link to the terminal? I ask because it would be a lot easier to do this. Again thanks a million for the teaching and advice. I really have learned a lot!

[Save Old Iron 1,563]

Zee,

I'm glad this is all working out as a low cost fix for your problem. This is another example of why my posts tend to be a little more drawn out or detailed. I believe with the right mixture of practice and theory, you can begin to do away with the guessing aspect of troubleshooting, and a great number of issues can be resolved without excessive trips to the auto parts store (or E bay) or excessive amounts of $$$ being spent needlessly.

To your question regarding the tach wire, you can attach the grey tach wire anywhere in the extra length of wire you inserted to repair the RR issue. In the low tech world of tractor charging systems, any point along that length of wire is the electrical equivalent of the left hand terminal on the stator. So yes, patch in the tach wire to your "extension" - no problem. Since we don't know the condition of the tach gauge, connect the tach wire with the tractor off. Start the tractor and monitor the tach closely. If you see any funny business with tach readings, shut down the engine as quickly as possible and disconnect the tach wire. Hopefully all will go as planned and the tach will function without further issues. Fingers crossed !!

[zeedubbya 18]

Spliced the tach into the left ac stator lead and it works great!! Thanks for all the information and help SOI! I hope that nutty staff of yours has that diploma ready because I learned a great deal from this! I now know a lot more about electrical and wiring in general!! Thanks so much!