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70wheelhorseGT-14

1993 520h

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70wheelhorseGT-14

I have a 1993 520H and this is my first 520. It has sat for 20 years and I've done a lot of work to it and it was running great. Went to the shop and had a rebuild kit for the carb and came back and I let it run for 1.5 hours when I got home and it was doing great. I've started it twice in the last week, Yesterday I was hooking up the lift arm  with a cable and running it to the hitch. Got that done and then started it. Worked the hitch up and down and all was fine. After about 2 minutes of the tractor running it cut off with no warning. Wouldn't start anymore last night. Get home from work and start it this afternoon and starts good and again runs for about 2 minutes and cut off. Wouldn't start anymore for almost 2 hours. I pulled the plugs and checked for spark and didn't have any. Checked wires and connections and were fine. 2 hours later I try to start it and runs good for 2 min. Then off. Wouldn't start anymore. I have no clue what's going on with it. Anyone able to shed some light on the issue I'm having?

 

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rokon

the 4 and 5 series onan tractors have known electrical issues with the fuse block and the white plastic 9 terminal connector in the engine harness. the issue is poor connection that leads to high resistance. check these and do a search on here for 520 electrical problems

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wrightorchid

High resistance also can create a lot of heat, and melt insulation.  There are various threads on here about the 9 pin connector and various improvements for better reliability.

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ohiofarmer

That fuse block and [if i recall correctly] another safety switch for the blade engage lever are located below the battery and in a very dusty/dirty environment. Penetrating oil fixed my fuse block. i do not remember exactly, but i think i wired around the safety switch.

 

Since i cannot remember exactly, please use this as a guideline as possible things to look for.

 

 The only other issue that stopped mine from running was a part that either looked like a rectifier and was a rectifier or had some other function. All I remember is that the teardown to get to it was not real fun. When I traded the identical part from my 416, the tractor ran so i ordered another. The 520 used up two of them in 1100 hours. That tractor is still alive with a predator engine when the OEM motor developed a noise. Anyway, a rectifier is part of the charging circuit and in that case your battery will not recharge. However, a battery left sitting might recover slightly and could re-start that engine and then die shortly after , as you described.. Get a multi-meter and check the voltage on your battery. A fresh battery should check at about 12.7 or so. Check and charge that battery [at no more than 2 amps] and see if your tractor runs again. If your battery runs down again, then the rectifier could well be the cause.

 

 Anyway, i do not wish to send you down some rabbit hole, but maybe the 520 experts can clarify these comments

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70wheelhorseGT-14

I appreciate any advice. I went and started it after work today and for 3 min you couldn't ask a mower to run any better then bam, cut off. wouldn't start again. Anyone have a wiring diagram for the 520? I'm still going to try the fuse block. I pulled the fuses out and blew the block out but didn't put any lube in there

 

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gwest_ca

Garry

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cheesegrader

Odd that it cuts off at the same time.

I wonder if something is heating up and shorting out.

The fuse block has been a sore spot for me.  If the wires are burnt, cleaning the block won't help.

I have replace the fuse block with sealed individual fuse holders on most of mine, and this has solved a lot of problems.

If everything goes out, including dash lights, I'm thinking fuse block, keyswitch or battery connections.

I have been fortunate to have NO 9-pin connector issues yet, but it is also a common weak point.

I have also had issues with relay switches.  My best tractor now has a sealed set of relays, moved into the battery compartment and away from snow and slush that I threw onto them plowing

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mancanic2

I have a 520h also. seat switch gave me all kinds of issues.. I installed an aluminum heat block by 9pin cured heat transfer issues also

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WVHillbilly520H

It could be the ignition module and rotor behind the flywheel ,Jeff.

IMAG2137.jpg

IMAG2139.jpg

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WHX??

Check the coil as well, they have been know to open after running a little. They can get hot and then not work. After a cool down they work. Can be done with a regular multi meter checking for continuity and power.

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ericj
On 2/3/2017 at 5:02 AM, WVHillbilly520H said:

 

It could be the ignition module and rotor behind the flywheel ,Jeff.

 

 

the ignition module is a common problem with the onans. I have had several onans with bad ignition modules on them. check the onan manual it will tell you how to check it. when it cuts out and won't start next time get a volt meter and put it on the negative terminal of the coil and the negative terminal on the battery, you should read 12 volts, now spin the motor over by hand slow. the voltage should drop to 1.5 volts and the go back to 12 volts, if it does not do this then the ignition module is bad. please double check the manual to be sure I'm explaining this correctly, it's been awhile since I did this so I want to make sure I telling you right. Isn't there a pinned thread at the top of a section on how to check your onan, not sure if it's in motors or electrical, it was started by Martin a couple of years ago.

 

 

 

 

 

eric j

 

 

 

 

 

 

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