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Herbl

520H blows 25amp fuse

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Herbl

I thought I had fixed the problem but it came back. But at least now it's not intermittent. When I turn the key On and don't try to start the machine up the 25amp fuse blows just with the key in On position. I know that we ask first about cleaning/replacing the fuse box and the nine pin connector and I have and they really look in nice shape. I'm just would like to go down a list of things to check because I believe if I just go down a list of things to do the problem will appear. Since I don't have anything running or switches (I believe) interfearing, I would believe this can be tracked down by process of elimination. Save Old Iron if your around and point me in the right direction I may have include a piece of good old Hudson Valley Apple (its that time of the year) with that coffee were going to have...

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Save Old Iron

I smell apple pie !!

Give me a few minutes to get settled here and I'll check the Demystification guide and come up with a few ideas.

Stay tuned.

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Save Old Iron

Herb, I cannot remember if your are more familiar with an ohmmeter or voltmeter or the "test light".

For a first look, I would inspect all the wiring coming out of the ignition switch for wear and tear and rodent damage. Any wiring contact with the tractor frame is an instant blown fuse.

If you have an ohmmeter.

Disconnect the battery terminals and disconnect the wire connector from the back of the ignition switch.

Always disconnect the battery cables from the battery when doing ohm checks. Sooner or later , it will save your meter.

Set the meter on the lowest ohms setting.

Connect one lead from the ohmmeter to the tractor frame (a good ground)

Connect the other meter lead to the YELLOW wire terminal to check for a short thru the PTO wiring. Any reading less than 0.5 ohms will blow a 25 amp fuse. I would expect the ohms reading should be significantly higher than 1 ohm if the wiring is not shorted.

If I understand you correctly, the 25 amp fuses blows BEFORE you try to move the ignition switch to the START position.

The ignition switch connects the "B" Battery terminal to the "R" regulator terminal, the "A" accessory terminal and the "I" ignition terminal.

In the 520's the "R" terminal is not used and the "A" accessories terminal is fused with a 15 amp fuse. Just for giggles, check the 15 amp fuse to see if it is intact.

I would also check the PINK wire coming from the "A" terminal to make sure it is not touching a chassis part BEFORE it enters the 15 amp fuse holder.

If you get a low ohms reading on the YELLOW wire I would visually check the wiring from the (I) terminal of the ignition switch. Check the wiring from all the PTO switches carefully for rubbing , bad connectors and other nonsense.

I'll be around tonight - keep me posted.

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Herbl

Save Old Iron, It's a little late for me now to check but will check tomorrow morning, of course I'll have to quit early as my Model A Club is having a picnic and I have to get the ol girl out for a ride, but you can be assured when this is all over there will be warm apple pie to be enjoyed.....Thanks

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Herbl

Good Morning Save Old Iron

Ok, before I leave to go to my club picnic this is as far as I've gotten, of course I got everything out the way (battery and tray etc:) and got all the equipment ready to tackle the job. By the way I can do volts or ohms either test you want I should have the equipment on hand, I even have one of those power probes just in case you seen the commercial on TV. I used the negative battery cable for ground and checked different spots of the frame and got 0.00 - 0.02, so I figured that was a good ground, I hope I'm right. When I put the probe on the yellow wire on back of the PTO switch I got 0.529, of course that is with the wire attached to the relay. Does that mean most likely it the PTO relay? I was looking how the heck do you remove the relay because I believe there are little nuts on the bottom and its pretty darn close against the side plate. Of well lets handle the issue at hand, so Save Old Iron I leave the question is the switch bad?

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300zx

Herbl, I don't know if you will have to take the PTO interlock off, but if you do, don't try to take the little bolts out first. Just remove the electrical wires and remove the bolt on the bracket that holds the interlocks (it also holds the grounding terminals). The bracket and the interlocks come off easily then and you can get to the smaller bolts after the assembly is out.

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Save Old Iron
When I put the probe on the yellow wire on back of the PTO switch I got 0.529, of course that is with the wire attached to the relay.

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Herbl

Chuck, thanks now I got something to really work with. I'll let you know my progress, again thanks and when this is over, well you know. By the way have you ever been to the Montgomery Place Mansion near Rhinebeck? If you haven't and you like to see old things let me know via email, please come as my guest...Sept 12th save the date...

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Save Old Iron

Herbl,

thanks for the invite, I used to live in Kingston back in the mid 70's.

I have been there a time or two. Make sure they let you feel the top of the mahogany lion's mouth near the fireplaces. The carving is so intricate , you can feel the ridges inside the lion's mouth !! Amazing old world craftsmanship.

I may not be able to break free any weekends for the next month or two. My daughter has just moved up to the St Lawrence seaway and we will be making several trips up that way to get her settled in.

I'll find my way down there sooner or later and grab some coffee. I promise.

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