L2850DT Fusible Link/Wiring Question

[Skidpad13]

Good morning folks, new member here. Recently got an L2850DT for a project after I'd sold my old MF30B. I needed 4wd. Anyway, it starts great, when it starts.

Recently it's taken to not starting at all. Lights come on the dash but no sound from the starter. Only sound is a relay under the front of the fuel tank so I'm thinking it's probably the timer relay engaging.

I've tested the neutral safety switch per the WSM & it reads 1.4 ohms resistance when the switch is pressed. That should be 0 (zero) ohms so problem #1 identified. I thoroughly cleaned & brightened the battery posts, battery cable clamps, ground connection to the chassis & the negative cable, & all three lugs that bolt to the bottom of the starter.

I haven't tested the voltage & resistance of the ignition switch yet but plan to. So, with all that said, here's my question.

Where is the fusible link supposed to be? The wiring on this has been, well, reworked/patched/etc... from the workshop manual (WSM) it looks like the link should be immediately in front of the starter but all that's there is cable with electrical tape wrapped around it. The wiring diagram shows the link somewhere between the starter & the ignition switch. Anyone with this model (it's the later generation of serial numbers) that could post a picture or shed any light on this would be greatly appreciated. I'm trying to avoid the cost of a whole new wiring harness if I can avoid it. Thanks!

 

[Skidpad13]

I'm guessing that it's where this red wire has been "twisted" together to "complete" the circuit.

 

[GreensvilleJay]

well that's a pain....
you could install an ATC fuse holder there though WHAT fuse ? A quik look on the net and NO proper description of the 'green fusible link' that is supposed to be there.....
You could also install a resettable circuit breaker IF you know the amp rating......

 

[PoTreeBoy]

I'm guessing that it's where this red wire has been "twisted" together to "complete" the circuit.

Yep. Looks like your original fusible link was 0.5mm^2 (20ga.). You could install a 40A slo-blow fuseholder and fuse to replace it.

 

[Dave_eng]

I'm guessing that it's where this red wire has been "twisted" together to "complete" the circuit.

On the starter solenoid there is a large terminal where the + battery cable is connected.
The purpose of the fusible link is to protect the entire electrical system.
The fusible link needs to be connected to the same terminal as the battery cable. Either directly or with a short length of heavy gauge wire between the starter post and one side of the fusible link.

Open the twisted together wires and when you do everything should go dark which is what a fusible link would do.
Depending upon your local auto supply place you could buy a modern slow blow fuse. Most places have the actual fuse but not the base so getting the base is the challenge.
The wire diagram you posted shows the fusible link gauge as 0.5 and while I have not looked that up 40 amps is the typical one.
From my files:

Dave

 

[Skidpad13]

Thanks guys, seriously. I'm sure we all know this tune "I've got to fix ten things so I can fix the thing I really need to fix". I am planning on replacing the o-rings & gaskets for the injector pump delivery valves this weekend but I need it running to get it into the shop. If it was easy, everyone around do it I guess.

Anyway, I'm going back down later to confirm that the B post on the alternator goes to this twisted connection & then on to the fuse block for the position 1 fuse. Based on my single-line I've drawn to isolate this circuit that's where the fusible link is supposed to be.

So, once I'm sure that's where it goes I'll look around for the appropriate connector to reinstall and either use the factory link or a more modern slow-blow fuse (40A) as you've suggested. The local dealer has the link in stock so if I can find the mating connector I may go back to factory design.

I've also ordered a new safety switch so hopefully that fixes it.

I'm suspicious of the starter from my experiences on my big case 590. I chased starting issues for months to include an Amazon replacement starter. Nothing fixed the problem until I coughed up the dealer money & installed a factory starter. 4 years later it's going strong.

One semi-related question: do you guys know what the numbers before the wire color mean on the wiring schematic? They're too small to be amperage. I don't recall seeing that before. I've circled a couple of examples on the reattached wiring diagram.

Thanks again!

 

[Dave_eng]

Thanks guys, seriously. I'm sure we all know this tune "I've got to fix ten things so I can fix the thing I really need to fix". I am planning on replacing the o-rings & gaskets for the injector pump delivery valves this weekend but I need it running to get it into the shop. If it was easy, everyone around do it I guess.

Anyway, I'm going back down later to confirm that the B post on the alternator goes to this twisted connection & then on to the fuse block for the position 1 fuse. Based on my single-line I've drawn to isolate this circuit that's where the fusible link is supposed to be.

So, once I'm sure that's where it goes I'll look around for the appropriate connector to reinstall and either use the factory link or a more modern slow-blow fuse (40A) as you've suggested. The local dealer has the link in stock so if I can find the mating connector I may go back to factory design.

I've also ordered a new safety switch so hopefully that fixes it.

I'm suspicious of the starter from my experiences on my big case 590. I chased starting issues for months to include an Amazon replacement starter. Nothing fixed the problem until I coughed up the dealer money & installed a factory starter. 4 years later it's going strong.

One semi-related question: do you guys know what the numbers before the wire color mean on the wiring schematic? They're too small to be amperage. I don't recall seeing that before. I've circled a couple of examples on the reattached wiring diagram.

Thanks again!

Wire cross sectional area which relates to current carrying capacity.
Look on the chart below. Green section shows 0.5mm2 which is what is on your diagram.

Dave

 

[Skidpad13]

Yep, I'm a complete idiot. I was trying to figure out how to understand it and then your post clicked. It's a kubota so the wire gauge isn't shown as AWG but metric instead. Now I get it. The 0.5 is basically 20 ga stranded. Thanks for recalibration my head unit (ha)!

 

[rbargeron]

Good morning folks, new member here. Recently got an L2850DT for a project after I'd sold my old MF30B. I needed 4wd. Anyway, it starts great, when it starts.

Recently it's taken to not starting at all. Lights come on the dash but no sound from the starter. Only sound is a relay under the front of the fuel tank so I'm thinking it's probably the timer relay engaging.
....................

The most common cause of no action at the starter is a poor connection at the small wire going to it on the end of the solenoid. Try shorting that spade to the starter's main wire connection. If the starter clunks and runs, 12v isn't getting to the solenoid (the starter's actual on-switch). take care, Dick b

 

[Skidpad13]

Thanks to everyone for the help. I think I've identified a big part of the problem. The previous owner intercepted the black & white wire coming from the safety switch & ran it up to a power block he installed & then brought another wire back down to attach to the spade you mentioned on the bottom of the starter. To power this "block " they ran an extension of the main positive power circuit up to the block using a heavy gauge (looks like #2 or #0) & jumped off the main lug on the starter. I have no idea why but I'm putting it back to factory spec to test if the problem (combined with the new safety switch) is resolved. I'll also use a new spade to send the signal to the starter. Of course, if this doesn't fix it it's either the wiring, the starter, or the ignition switch but the presence of this jury-rigged setup combined with the resistance reading of the switch gives me hope for resolution.
Thanks!

 

[Dave_eng]

The block as you refer to it is actually a heavy duty relay often found on older Ford vehicles and also garden tractors.
John Deere came out with a relay kit to help tractors with starting difficulties as the numerous safety switches aged and developed too much resistance to trigger the starter solenoid.
It looks like the previous owner was copying this system.
Here is the John Deere literature. Many have copied there design with a cheap automotive relay. Newer tractors now have a relay to trigger the starter as part of the original design.

This is the type of relay now on your tractor.

Dave

 

[Skidpad13]

Well, that certainly explains the loud relay closing sound i hear whenever the key is turned. I didn't think it would be the timer relay to the right. I will probably do some voltage drop testing to see which configuration produces a higher voltage at the solenoid connection before removing it entirely.

I thought it might be a relay with the infeed & outfeed lines. The only thing I could imagine was that maybe there had been something else attached to the machine before I got it that would need that much power. Thanks for the heads up!

 

[Mark_BX25D]

I have no idea why but I'm putting it back to factory spec to test if the problem (combined with the new safety switch) is resolved.

This is the smart thing to do. Once it's stock, the wiring diagrams can be used. Online advice starts making sense. Things fall into place.

 

[Russell King]

Hey @Dave_eng or any other person that understands that relay wiring-
I have not thought about it for some time but notice that the second terminal on the “small wire” side is not connected to any thing. I think that normally that would be grounded to complete the circuit and wondered if that would make this a more robust system?

I assume that it is currently grounded by the case and that ground may be getting “iffy” in completing the circuit and could be improved by grounding it directly to the battery

 

[Dave_eng]

Hey @Dave_eng or any other person that understands that relay wiring-
I have not thought about it for some time but notice that the second terminal on the “small wire” side is not connected to any thing. I think that normally that would be grounded to complete the circuit and wondered if that would make this a more robust system?

I assume that it is currently grounded by the case and that ground may be getting “iffy” in completing the circuit and could be improved by grounding it directly to the battery

Russell
There are a number of variations of the larger style Ford starter solenoid/relay.
Back in the days when cars had ignition points and condensers, ballast resistors were added to the ignition circuit to lower the stress on the points.

The trouble was the spark from the plugs was too weak to fire up a cold engine. Solution, bypass the ballast resistor during starting. The second smaller terminal on the starter solenoid was used to provide by pass power directly to the ignition coil. Not unlike the key switch on older style Kubota glow plugs bypassing the glow indicator during starting.
On some models of Ford style starter solenoids, the case was not the ground but rather the second small terminal was. Now primitive safety features like no crank unless the clutch pedal was depressed were put into the starter circuit using the second small terminal.
Unless you studied a particular solenoid of the style in question with a multi meter doing anything to it now could just create more problems.
Replacing the existing with a modern John Deere style relay would likely improve starting.
The old relays were designed to be switching starter level current. Using that relay to trigger an integral solenoid likely has not switched enough amps to keep the contacts clean.
Dave

 

[Russell King]

Thank you for the information. I had never messed with those larger relays very much to remember all the wiring details.

Good explanation of the details

 

[Skidpad13]

Following up on this. I replaced the safety switch that was giving higher than spec resistance. Problem still exists. I'm charging & running the battery through a repair/desulfating cycle on my charger just in case. It's a 2019 battery so not that old.
In the spirit of only fixing one thing at a time to be sure that I've caught the problem, I wait for this to finish & replace before moving on.
However, the mtster of the missing fusible link still persists. So I have the replacement link from kubota but the wiring harness pigtail is missing since the PO removed it.
I've removed the wire that comprises the link from the plastic housing since I have been unable to locate a matching female side. Here are my thoughts & I'd be open to all critique or advice.

Option 1: leave the male side as factory & use two individual female connectors to join this into the wiring.

Option 2: remove the brass terminals from this magic green "wire/fusible link" and install the wire into a No.12 Deutsch connector as an "in/out" loop. See attached sketch. I realize that a no. 12 connector is nominally rated for 25amps continuous but this "wire" looks smaller than a stranded AWG12 wire.

Option 3: take my lumps for the $11 fusible link & install a 40A slow-blow fuse as has already been suggested.

Thoughts or opinions?