NH TL90 solenoid ignition wire not connected

Hello Sanch welcome to the TF! I know nothing about your NH, but are you sure that the circuit you followed to did not branch off the main start circuit and has just led you to a plug that is unused? I cannot hardly think that a plug came unhooked to cause your problem and you cannot find where it should plug back into. Unless you have had a lot of the wiring in that location disconnected for a repair. Please double check this. A neutral switch or other type of safety item causing an “open” in the start circuit would be a far more likely problem. Any chance rodent damage is your problem?

Start with a test Light at the ignition switch to see if there's power there, and work back towards the Solenoid , the Key turned On should send 12 vts to your dash lights etc. - at the Start position it should only go to the Solenoid

Thanks for you're replies.

With the ignition in the start position I have no voltage at the starter solenoid ignition wire.

When I supply 12v to the plug behind the dash the tractor starts as normal.

Just so I understand this correctly, you're saying it's possible that the starter solenoid ignition wire branches off into the ignition circuit and that plug is unused?

There is a possibility that the forward and reverse shuttle lever is malfunctioning as I have had issues with this in the past. I think that would cause an open in the start circuit.

Have you checked and found the start spade on the ignition switch?, this is the second test to do after finding if there is battery power to the ignition switch.

If the first two tests are ok, then connect the starter hot wire to the ignition switch and check if the tractor will start, if not, then start tracing all of the safety sensors for a fault, you have mentioned you feel the forward reverse shuttle could be playing up, disconnect from the shuttle sensor and make a temporary bridge to find out if that is your problem.

FredM said:

Have you checked and found the start spade on the ignition switch?, this is the second test to do after finding if there is battery power to the ignition switch.

If the first two tests are ok, then connect the starter hot wire to the ignition switch and check if the tractor will start, if not, then start tracing all of the safety sensors for a fault, you have mentioned you feel the forward reverse shuttle could be playing up, disconnect from the shuttle sensor and make a temporary bridge to find out if that is your problem.

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Easier said than done. You're talking about a multi pin harness connector on the shuttle switch. There's no simple way to interrupt that harness, isolate any one or two circuits, and perform any kind of tests. Same holds true for the PTO switch. Yards and yards of small gauge wires, all encased in protective mesh that must be cut open to reach any individual wires. Most of that is tucked in behind overlapping plastic panels, many of which break before they separate. The TL 90 was produced for five or so years, and the wiring circuits for each model year could be slightly different from the last.

Your thoughts may make sense in theory, but prove very difficult to accomplish in practice.

Fedup, I appreciate you adding the information about the electrical system being a bit more complex than our reply merit. So you seem to have some knowledge of the system and have “taken the reins” go ahead and steer us. What do you have to offer about his mystery plug that appears to be part of the start circuit but seems to have no spot to plug into? I could venture to guess that it is for diagnostic purposes. Without a wiring diagram there is a lot of guessing going on.
Sanch, in this link is a downloadable service manual for your tractor. I would suggest purchasing one.
NH TL90 service manual

Fedup said:

Easier said than done. You're talking about a multi pin harness connector on the shuttle switch. There's no simple way to interrupt that harness, isolate any one or two circuits, and perform any kind of tests. Same holds true for the PTO switch. Yards and yards of small gauge wires, all encased in protective mesh that must be cut open to reach any individual wires. Most of that is tucked in behind overlapping plastic panels, many of which break before they separate. The TL 90 was produced for five or so years, and the wiring circuits for each model year could be slightly different from the last.

Your thoughts may make sense in theory, but prove very difficult to accomplish in practice.

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Righto Fedup, note taken, not your standard tractor then, so I will back out.

A few years back, I had the same issue with a massey. No start, wire traced under the dash and at first glance, no place for it to plug into the ignition switch. On closer inspection I found the spade terminal on the switch had corroded off requiring the purchase of a new switch. If supplying 12v to your loose wire starts the tractor, I'd look closer at your switch

Sanch012 said:

Hi, I have a tl90 new holland. The starter solenoid is not working when I turn the ignition on to start. I have traced the starter solenoid ignition wire to behind the dash, which is not plugged in. I can't find where this wire is supoosed to be connected.

Can someone help me with this please?

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it will go to the terminal marked S on the switch. but most of the time it will be a safety switch on the seat or pto that will stop the ignition switch from supplying voltage to the solenoid

I use red mn said:

Fedup, I appreciate you adding the information about the electrical system being a bit more complex than our reply merit. So you seem to have some knowledge of the system and have “taken the reins” go ahead and steer us. What do you have to offer about his mystery plug that appears to be part of the start circuit but seems to have no spot to plug into? I could venture to guess that it is for diagnostic purposes. Without a wiring diagram there is a lot of guessing going on.
Sanch, in this link is a downloadable service manual for your tractor. I would suggest purchasing one.
NH TL90 service manual

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Actually, I have no truly worthwhile suggestions so I haven't offered any. And yes, I am familiar with the tractor and electrical issues with them. I really don't remember if 90 series tractors had a formed plastic unit that plugs onto the key switch or if it's all individual single wires.

This is what the switch looks like, and I would expect pin 50 will be the start signal.

Thanks everyone.

It does have a formed plastic unit that plugs onto the key switch. I will test the voltage at the ignition switch today and see what I find.

Fedup said:

Actually, I have no truly worthwhile suggestions so I haven't offered any. And yes, I am familiar with the tractor and electrical issues with them. I really don't remember if 90 series tractors had a formed plastic unit that plugs onto the key switch or if it's all individual single wires.

This is what the switch looks like, and I would expect pin 50 will be the start signal.

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I tested the ignition switch today and there is 12v on the start pin so no issue there.

I am expecting it to be a faulty forward and reverse shuttle lever at this stage, unless someone else had any more suggestions.

Your choice here, but before I ordered that switch I would probably go the start relay first. It would be on a panel of relays, somewhere in the cab, probably inside the right door, and down low on the inner fender console under some plastic panels. At least I THINK that's where they put it on TL series tractors. The guide sheet on the cover should identify which relay is which. Pull the relay and test the pins behind it with a test light. See if there's power to any of them with or without the key in start position. The load circuit from there should go straight to the starter solenoid, so if you put a 12v jumper to it the starter should engage. It may help you to play around there a little.

I ended up getting a mechanic to take a look as I needed the tractor. The issue was that the clutch dump switch needed adjusting. I'm not familiar with that term but I'm assuming it is the switch on the clutch pedal.

Thanks for all your input on my question