MF 202 Wiring

[camohn3]

[size=18:3f12fa737c][/size:3f12fa737c]The MHF-202 sitting in my field, with a toasted wiring, needs rewiring. It is an older machine SN 30061 making wiring schematics hard to find. I have a picture diagram showing components and wiring but wires are bundled into a harness so one can not tell how to connect one end. So, not being a "tractor guy" but am willing to learn each day. Any help would be welcome.

 

[Steve@Advance]

Welcome camohn3!

The wiring on those is really simple and basic.

As long as the wiring harness is still somewhat intact, even if it is melted, each wire can be picked out and replaced one at a time. Do the easy ones first, and as you get to the end it starts to make more sense.

To me, buying a premade harness is harder to install than just making one from scratch. Never fails, something doesn't get routed exactly right, and 3/4 way through one of the wires is too short! Very common for electrical to have been changed over the years too, especially the charging system, so no guarantee a harness would be 100% right.

Look at the wiring of similar models of those year tractors, that will get you in the ballpark.

All the wire can be 14ga except the alternator and the amp gauge wire, those are 10ga. The black plastic split loom harness sheathing from the auto supply, and a bag of wire ties will make for a professional looking and protected job.

Don't be shy about asking questions, we can walk you through this.

 

[camohn3]

(quoted from post at 15:37:50 07/18/19) Welcome camohn3!

The wiring on those is really simple and basic.

As long as the wiring harness is still somewhat intact, even if it is melted, each wire can be picked out and replaced one at a time. Do the easy ones first, and as you get to the end it starts to make more sense.

To me, buying a premade harness is harder to install than just making one from scratch. Never fails, something doesn't get routed exactly right, and 3/4 way through one of the wires is too short! Very common for electrical to have been changed over the years too, especially the charging system, so no guarantee a harness would be 100% right.

Look at the wiring of similar models of those year tractors, that will get you in the ballpark.

All the wire can be 14ga except the alternator and the amp gauge wire, those are 10ga. The black plastic split loom harness sheathing from the auto supply, and a bag of wire ties will make for a professional looking and protected job.

Don't be shy about asking questions, we can walk you through this.

Thank you, I understand the process you have suggested, and I will do just as you suggest. But, when I came into possession of this machine there where wires cut off with no matching end I see. The big problem is where does the position neutral switch fit in the circuit, this is not clear on the schematic I have looked at. Can you tell me if this switch on and off with the key? And is it wired one side + and other -? Any way I'll get into it and check back with my questions, thanks again.

 

[Steve@Advance]

The neutral safety switch is wired between the start terminal of the ignition switch (or push button, whatever it uses) and the small terminal of the starter solenoid.

It is not polarity sensitive, just a set of contacts that close when in neutral, open when in gear.

 

[camohn3]

(quoted from post at 19:24:45 07/18/19) The neutral safety switch is wired between the start terminal of the ignition switch (or push button, whatever it uses) and the small terminal of the starter solenoid.

It is not polarity sensitive, just a set of contacts that close when in neutral, open when in gear.

That is exactly what I needed to know, check in with you later. Thanks

 

[camohn3]

If you would review the following wiring connection that have been completed and comment.
Starting at key switch - three pole, single throw
Line connected to top tab of voltage regulator
Switched terminal A connected to start PB
Switched terminal B connected to coil
Starting Push Button spring loaded momentary contact
Terminal A connected to key switch
Terminal B connected to one side of position neutral switch
and terminal of coil of the starter solenoid - see note below
Position Neutral switch
Terminal A connected to load side of starter PB
Terminal B connected to starter solenoid coil connection
Starter Solenoid
Line side connected to + of battery
Load side connected Starter motor

Not yet wired are:
Generator - existing wiring look to be intact
Position neutral switch - need to get "disconnect or bullet crimp on connectors to complete. Wiring of this switch looks to be the cause of the shot. Both wires insulation are completely burned off.
Amp meter - is connected to the two remaining terminal of the voltage regulator.

Would have liked to send an image of schematic that shows above but having trouble with scanner right now. Any and all comments will be appreciated. Charlie

 

[Jim.ME]

My thoughts, for what they are worth. I wouldn't hook the ammeter to the two remaining terminals of the voltage regulator. To work properly one terminal of the ammeter should be connected to the power source, usually with the battery cable at the solenoid or starter. The other terminal of the ammeter should have the loads and wire from the regulator's Battery terminal connected to it. The regulator should have terminals for battery, generator field and generator armature. Depending on the regulator, it might have a 4th terminal for load and some had a ground connection.

Regulator terminals are often marked as to what they go to, look closely at each tab between the screw terminal and regulator base. Physical position might not be the same as function.

Do you have a sheet that calls the key switch terminals out as A, B, C, and gives the function of each or is that how you are identifying them? If not have you checked function as related to key position of each terminal? The letters (A,B,C) alone don't tell what should connect to them. Many key switches are marked (Ign, Bat, A, S, etc.) beside the terminals as to what should connect to each.

Your connections may be right; when you can post your schematic it will help confirm things.

You may already have some like these but here are a couple MF schematics, that should be similar to your tractor's, which may help as well.

 

[camohn3]

The diagrams you posted are of great help. I have no electrical documentation for the machine, only the wiring as it came to me, which is a story by it self. I would say the wiring was not entirely correct to start with but the short causing the melt down was an attempt, by me, to connect a loose wire end. The A,B, C references I make are only to make myself clear. I will inspect the regulator closely for marking of terminals. The ignition switch has been check with an ohm meter to see how it operates but there are markings on it as I'm seeing in the diagram posted. It will have to be looked at again. From what I see I'm close but still not 100%. Question: The major fault was with the wiring of the position neutral switch, the wires burned all insulation off. This makes me think the switch may be burned as well. How does the it work? Is there a coil that actuates a plunger?

 

[Jim.ME]

The neutral switch is just a mechanical switch. When the transmission is in neutral position the contacts close to allow current to pass. Here is an old post on testing the switch.

https://forums.yesterdaystractors.com/viewtopic.php?t=1047897

You can find and order the operator's and service manuals from AGCO at their books site http://www.agcopubs.com/, in several different formats. There is also a phone number there if you want to talk with customer service to be sure you get the right ones.

You can access the parts catalog for free at https://apb.agcocorp.com/ sign in as a guest user.

 

[camohn3]

I'm starting to feel good about getting this done, thank you.

 

[camohn3]

Project completed successfully!!! Thank to all who helped me.