B1700 - new 30A fuse blew immediately on start

[tbronson]

Replaced the 30A box fuse, and on first attempt to start, it blew. I'm pretty sure I could hear the pop.

The previous fuse was replaced a year ago, and starting was fine, until the last couple weeks. Then it started to sometimes be dead on turning the key: after preheat, there was no click. This would happen once or twice, and then, after trying again, it would turn over. I think the number of tries it took to start increased in the last few days.

Yesterday, when it wouldn't start after many attempts, no click, I checked the fuse and it was blown. I replaced it, tried to start it, and heard a little pop. Checked the new fuse and it was blown.

Any idea what the problem is?

ALSO: This may be unrelated, but in the last few weeks, sometimes on starting, the engine would begin to turn over but not catch, as if the battery was too weak, and I'd hear a single dull, metallic clunk from somewhere under the hood.

Thanks.

 

[imnukensc]

You have a short someplace. It could be the switch, but it could be anywhere.

 

[Dave_eng]

To be clear, the fuse you are referring to is a pink slow blow fuse like the one below?

If this is the fuse, then it is like the master fuse for the entire tractor.

The B1700 could have a dynamo or an alternator for charging the battery.

Since your fuse is a 30 amp I assume you have a dynamo but please confirm.

When a master fuse like this one is blowing and no small fuses are, it narrows down the possible problem areas.

I suggest you start by unplugging the rectifier and the engine stop solenoid then see if the fuse blows.

Dave

 

[tbronson]

Yes, that's the fuse. And I believe it has a dynamo.

Do I need a supply of fuses in case they keep blowing? I won't be able to get new fuses until tomorrow.

How do I identify the rectifier and the engine stop solenoid?

 

[Dave_eng]

Yes, that's the fuse. And I believe it has a dynamo.

Do I need a supply of fuses in case they keep blowing? I won't be able to get new fuses until tomorrow.

How do I identify the rectifier and the engine stop solenoid?

The stop solenoid will be attached to the fuel injection pump and look like this one. Let me know if your solenoid wiring connector has one wire like this one or two.

The rectifier will look like this.

Ypou will need 3 to 4 fuses. If your handy with electrical stuff, you can rig up something to have you using the much cheaper fuses style but you may feel it is easier to just try what I have suggested to see if you quickly find the problem.

You need to be looking for mice nests or chewing damage to the wiring.

Please post some photos of your engine from both side so I can see if something stands out.

Dave

 

[tbronson]

I have 3 new 30A fuses. The 4 fuses in the fuse box look fine. I'll check all the wiring that I can see, and the stop solenoid and rectifier. Here's both sides of the engine:

 

[tbronson]

So far, I've followed every bit of wiring that I could see, looking for damage and crossed wiring, and found nothing. I then inserted a new fuse, turned the ignition switch to the preheat position, the indicator lights light up for about a second, and the fuse blew.

Locating and disconnecting the stop solenoid and rectifier is my next step.

Could the ignition switch cause this?

 

[Dave_eng]

So far, I've followed every bit of wiring that I could see, looking for damage and crossed wiring, and found nothing. I then inserted a new fuse, turned the ignition switch to the preheat position, the indicator lights light up for about a second, and the fuse blew.

Locating and disconnecting the stop solenoid and rectifier is my next step.

Could the ignition switch cause this?

It would be rare for a key switch to be the cause of your problem.

I looked more closely at the photos you posted earlier.

There is one spot where things do not look right.

Dave

 

[tbronson]

Here's a close-up of "does not look right" -- that's how it's been since I had the starter rebuilt around three years ago.

Here's the wiring behind the dashboard:

 

[whitetiger]

Here are the wiring schematics for your unit.

 

[tbronson]

I'm kinda stuck. If it's a short or a failed part that I can fix, I'd like to do that. Calling in a mechanic is expensive. But I'm not sure what to do after visually examining all the wiring I can see. Dunno how to use the schematics.

Is there any way to access more wiring without having to take the tractor apart? For example, it doesn't seem like I can get behind or remove the firewall easily.

What's the next DIY step, if there is one? What does disconnecting the stop solenoid and rectifier do?

Thanks!

 

[Dave_eng]

I'm kinda stuck. If it's a short or a failed part that I can fix, I'd like to do that. Calling in a mechanic is expensive. But I'm not sure what to do after visually examining all the wiring I can see. Dunno how to use the schematics.

Is there any way to access more wiring without having to take the tractor apart? For example, it doesn't seem like I can get behind or remove the firewall easily.

What's the next DIY step, if there is one? What does disconnecting the stop solenoid and rectifier do?

Thanks!

Disconnecting the two items tells you a lot. If the fuse stops blowing then the possible culprit has been identified.

I suggested the two items which could have failed internal components

The connector for the regulator is clearly visible in the last photo you posted

Dave

 

[torch]

Think about this for a moment: most circuits on the tractor are protected by a lower rated fuse. If the problem was with, say, the headlights then the headlight fuse would blow before the 30amp main fuse. So the problem must be somewhere that is only protected by the main fuse. The fuse only blows after the key switch is turned on -- possibly only after turned to preheat -- so it must be after the key switch.

Looking at the wiring diagram, power comes from the battery to the solenoid on the starter, and from there to the main fuse. So it's not the area that "doesn't look right", because that's before the main fuse.

From the main fuse it branches in 3 directions. One to the Regulator/rectifier, one to the 5A hazard fuse, and one to the main switch terminal 30. The main switch then sends power in 3 directions -- AC terminal, 19 (preheat) terminal and 50 (start) terminal. The fuse blew before you hit Start, so we can discount 50.

The AC terminal goes directly to the fuse box with a red with white stripe wire. That r/w wire could be rubbing on something and shorting out, but every circuit it feeds is protected by lower rated fuses.

Terminal 19 (preheat) splits 2 ways -- one to the glow plug indicator and the other to the glow plugs themselves. Neither is fused. Both are fed via plain black wires.

You indicated that you have had starting problems in the last few days. That could be an indicator of a problem in the glow plug circuit. EG: a partial short preventing full heating.

I would start with a very careful investigation of the glow plug and glow plug indicator circuits.

 

[Dave_eng]

Torch

I see the starter wiring a bit different.

There is a wire from the starter motor terminal on the solenoid which goes to the pull in coil on the fuel shut off solenoid.

Dave

 

[torch]

Red/black wire is fed from 5 amp fuse. The other two are both grounded, according to the wiring diagram.

 

[torch]

I think there is an error in that wiring diagram. It makes more sense that the wire to the starter is fed from the secondary contacts on the starter solenoid.

Still, that should only receive power when the key is in the start position and the starter has engaged. And it would be getting power direct from the battery (through the solenoid), not through the fuse.

 

[tbronson]

Thanks! That discussion is super-interesting, I'm learning from it. Is there a conclusion?

Meanwhile, I was about to try disconnecting both the rectifier and the stop solenoid, but ran into a problem. Where it's positioned, I can barely get a grip on the solenoid connector, and it doesn't budge when pulled. I think there's a latch from looking at the photo, but can't get at it anything to move. Worried that if I put too much force I'll tear out a wire.

How do I get that apart?

I'll try with the rectifier and stop solenoid both disconnected, as the next step. I still have 2 fuses, and can get more on Monday.

(This is going so slowly on my end because I've been mostly off-farm for the last few days.)

 

[GreensvilleJay]

Don't bother disconnecting the stop solenoid. Acording to the diagram, it's fed from a 5 amp fuse, so the 5 amp fuse would blow if the solenoid was shorted.
There's only 2 items that get fed from the 30 amp fuse, the rectifer/regulator and the ignition switch.
It's unlikly the switch is grouding out, but check the big red wire coming from the 30A fuse, maybe it's cut and grounding.
I suspect the rectifer/regulator though. An internal short will blow the 30A fuse.Disconnect that, put good 30A fuse and see what happens. You can run the tractor with it disconnected,

 

[tbronson]

Tried with the rectifier disconnected and the fuse blew immediately on turning the key to preheat. Feels exactly like the last attempt.

The key goes to the On position and one indicator light goes on (oil temp?). When I continue rotating the key to the preheat position, the preheat light blinks on and the fuse blows.

What's the little black plastic box, also wired, beside the rectifier? It's to the right of the rectifier in the photo above.

Stop solenoid next? There seems to be disagreement about that. I'll try it but I have only one more fuse, plan to get more tomorrow.

 

[torch]

Terminal 19 (preheat) splits 2 ways -- one to the glow plug indicator and the other to the glow plugs themselves. Neither is fused. Both are fed via plain black wires.

You indicated that you have had starting problems in the last few days. That could be an indicator of a problem in the glow plug circuit. EG: a partial short preventing full heating.

I would start with a very careful investigation of the glow plug and glow plug indicator circuits.