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fatboycowen

518xi - possible electrical problem

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fatboycowen

I'm in need of some help, with my 518xi. I've had it around 6 or 7 years now. Up to 680 hrs +/-.  The battery light is generally always on when running, since purchase, but it will sometimes go off eventually, when run a really long time. This has never caused a problem. Until this year, I have never put a charger on it, or jumped it. 

This year, the starter sounded weaker than usual, some times, and one day, it finally wouldn't crank, so I bought a battery and installed it. Old one was 2014 dated, so I figured that was the problem. The battery cables and terminals were clean. Tractor was fine with new battery, for 2 or 3 mows. 

Today, I disengaged the PTO to get another beer, and the PTO wouldn't engage again. I can hear it click, and I can hear the clutches scraping lightly. I think it doesn't have enough voltage to engage fully. I pulled it in the shed, shut it off, and it would no longer crank. Voltage down to 11.75. 

So, I jumped it, and it started easily. Put a volt meter on, and it seems to be drawing voltage when it's running. The voltage slowly decreases on the volt meter. 

I went through the wiring. Something is funny with the ignition switch. In the Lights position, moving the key slightly, I can hear a solonoid click on and off randomly. So, I ordered a new ignition switch. Could this be causing the tractor not to charge while running? Is this likely the problem? 

What else should I check?

 

Thanks! 

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gwest_ca

Could you post the model number and serial number of your 518xi?

There are 2 different wiring diagrams.

The charging output from the engine goes to a 25 amp fuse and then to the ignition switch and the ignition switch connects the charging current to the battery so yes the ignition switch could be at fault.

Click on the pictures in each link to see or download them.

1998

1999-2001

Garry

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fatboycowen

Thank you Garry. 

Model # 73471

Serial # 9900252

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fatboycowen

So, my problem is not fixed. The ignition switch was faulty, but the new one didn't fix the issue. I don't believe the engine is charging the battery. When running, the battery voltage is around 12.5. It creeps up very slowly (.01 every few seconds), but loses voltage when the lights are on, or when the PTO is engaged. 

 

How can I locate the problem? I've read that I need to check the regulator, but that's a rare issue. I've also read that the stator can lose magnets. Do I need to pull the engine to get to the stator? 

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gwest_ca

Here is the engine service manual.

Try this if you can get to the voltage regulator DC+ terminal.

With the key in the run position but the engine not running.

Measure the voltage across the battery posts.

Now measure the voltage at the regulator DC+ terminal.

It should be the same.

This verifies the charge current can get to the battery. Both sides of the 25 amp fuse should give you the same reading.

 

Garry

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fatboycowen

Great news. The tractor seems to be fixed. 

TL:DR - melted wiring connector.

 

As a temporary measure, I installed a solar battery tender in my shed, which I wanted to do anyway, which topped up the battery between uses, and allowed me to mow. Yesterday, the battery seemed to drain even quicker than usual, and the PTO wouldn't activate once it got too low. So, I used the spare time to troubleshoot.

 

Looking for the regulator, as Garry suggested, I found a bad wiring connector. the regulator is tough to access, but can be found on the left side of the engine bay, behind the side panel closest to the firewall, way down low near the frame rail. Where the voltage regulator is, there's a purple wire and connector. This was good. Beside it is two white wires and a connector (just a loose connector) The connector was melted. I couldn't figure out if it had melted from a short, or some other source of heat, but it was ugly, and had a ton of dirt and grime in it. I pulled it apart, cut off the connectors and added some new wire connectors, charged the battery and fired up the tractor. Poof, she's charging at 14.25 +/- volts. 

 

I'll report back if I run into any other problems. If anyone can speculate on why the connector might have melted, let me know. Would it melt because it was touching the engine block? It appeared to be factory, so I would think it would withstand the conditions. 

 

Thanks to Garry for the help. 

 

Jon

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gwest_ca

Suspect a terminal to terminal connection was loose or oxidized. That causes resistance to current flow = heat.

 

Garry

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