MF 40 Neutral Safety Switch and wiring help (2024)

Billmac said:

I launched into a project to get my old MF 40 with a front loader to charge. After putting it back the way it came and hooking up the exciter wire the way the electrical man told me, not I can't even get it to crank. I suspect I may have disturbed one of the wires relating to ground or unplugged the wire from the neutral safety switch. I actually own one of the worthless shop manuals that has no information on electrical systems.
So I plead your help for a location of the safety switch and possible routing of the wires, and if there is a wiring diagram for a one wire alternator, I would appreciate that also.
I still have not determined where the negative battery cable is attached after looking for 30 minutes. If you have ever worked on one of these, you know that everything is hidden under the manifold, carb, or frame. You can't get to the starter solenoid until you take all this stuff off. I'm probably going to cut off the ground cable, put a new one on, and attach it to the frame where I can see that it is secure. I thought I had seen the neutral safety switch years ago, but that was probably on a different tractor. If you know where it is and how to get to it, PLEASE HELP.
Bill

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Welcome to the Forums

Look for the neutral switch just ahead of the transmission cover right front corner.

I don't see that you have said if it is gas or diesel. You mentioned you hooked up the exciter wire the way the electrical man told you. An exciter wire indicates you have a three-wire alternator, internally regulated. The parts book shows the 40 as using a Delco 10DN externally regulated alternator (used before the internal regulated alternators). Does your tractor have an external regulator for the alternator? You ask if there is a drawing for a one-wire alternator, are you looking to do a conversion? The answer to that is not OEM as they didn't have one-wire alternators. As for the wiring diagrams, I expect they are in the Operator's Manual. Massey Ferguson often put those in the Operator's Manuals, not the shop/service manuals during that time frame. I don't have a manual for a 40, but may have one similar depending on what you are looking for and need for wiring info.

Here are the three Types of Delco alternators, which do you have now?

Billmac said:

I launched into a project to get my old MF 40 with a front loader to charge. After putting it back the way it came and hooking up the exciter wire the way the electrical man told me, not I can't even get it to crank. I suspect I may have disturbed one of the wires relating to ground or unplugged the wire from the neutral safety switch. I actually own one of the worthless shop manuals that has no information on electrical systems.
So I plead your help for a location of the safety switch and possible routing of the wires, and if there is a wiring diagram for a one wire alternator, I would appreciate that also.
I still have not determined where the negative battery cable is attached after looking for 30 minutes. If you have ever worked on one of these, you know that everything is hidden under the manifold, carb, or frame. You can't get to the starter solenoid until you take all this stuff off. I'm probably going to cut off the ground cable, put a new one on, and attach it to the frame where I can see that it is secure. I thought I had seen the neutral safety switch years ago, but that was probably on a different tractor. If you know where it is and how to get to it, PLEASE HELP.
Bill

Click to expand...

This is the neutral safety switch on my 165.

Roki6606 said:

Hi Bill,
I have a parts book for a Massey Ferguson 40 tractor. It shows a good break down of the different parts of the unit and how stuff goes together.
Not sure if this would be useful to you. I would sell it if you are interested.

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Wrong parts book for his tractor. He has a Massey Ferguson MF 40 industrial tractor, not a Ferguson 40 which is the manual you have.

Jim.ME said:

Wrong parts book for his tractor. He has a Massey Ferguson MF 40 industrial tractor, not a Ferguson 40 which is the manual you have.

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Gentlemen. Thank you for your inputs. You tried to help me and I appreciate that effort.

I still have not found the source of the neutral safety signal, so today, I'm going to get serious. Attach the starter solenoid directly to the starter terminal on the ignition switch which will bypass the safety feature for awhile.
The safety switch works off the high low neutral lever on the transmission which must be in neutral or the tractor is not supposed to start. Somewhere there is a plunger that hits a switch that apparently breaks the connection.
It's now hot in Texas. I'm getting closer to shoving this yellow POS into the nearest brush pile and setting it on fire. Ha. The solenoid could also be bad and I just need to get to the terminal end of the wire to see if the signal is getting there. As I said, doing anything on this tractor requires a half day of trying to gain access to what you are trying to see. My wife says 'call the guy'. NEVER! Thanks again.

Billmac said:

Gentlemen. Thank you for your inputs. You tried to help me and I appreciate that effort.

I still have not found the source of the neutral safety signal, so today, I'm going to get serious. Attach the starter solenoid directly to the starter terminal on the ignition switch which will bypass the safety feature for awhile.
The safety switch works off the high low neutral lever on the transmission which must be in neutral or the tractor is not supposed to start. Somewhere there is a plunger that hits a switch that apparently breaks the connection.
It's now hot in Texas. I'm getting closer to shoving this yellow POS into the nearest brush pile and setting it on fire. Ha. The solenoid could also be bad and I just need to get to the terminal end of the wire to see if the signal is getting there. As I said, doing anything on this tractor requires a half day of trying to gain access to what you are trying to see. My wife says 'call the guy'. NEVER! Thanks again.

Click to expand...

Looking rearward from the starter, work your way back towards the transmission. The switch is in the top of the transmission housing forward of the dash panel, close to in line with the Hi-Lo shifter. It may be behind a panel.