# Massey 175 gauge wiring issues



## Windy99 (9 mo ago)

I am working on a 1974 Massey Fergurson 175. Initially I just wanted my fuel gauge to work!!! Then I noticed a wire coming from the oil pressure switch to the ammeter was fried and someone put black tape on it! So, I bought an operator's manual that show the wiring diagram for my tractor, however it is for a generator, and I have an alternator! The diagram shows a pink wire from the fuel gauge to the oil pressure switch. (There was no such wire to be found). My oil pressure switch has 3 flat prongs, 2 copper and one silver. The silver had no wire attached. One wire from OP Switch went to voltage regulator and one wire that was burnt went to ammeter. The diagram is showing an open circle where the fuel gauge hooks up to and a solid circle where it says "terminal having adjusting set screw" which I do Not have! My oil pressure switch is not like that! I don't know why the wire was burnt and most wires in gauge area were all sorts of aize wires not 18ga wires. If I run it like it was with the OP Switch to the ammeter then I have no place for fuel gauge wire. Some post I have read said fuel gauge wire goes to ammeter????? When I cranked my tractor up after new wiring all gauges worked and the
second time none of them worked and the third time the starter started to continually spin to the point I had to remove battery cable to get it to stop!!!! Now I am a bit scared and frozen in place! Can anyone help with this mess Please?????


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## FredM (Nov 18, 2015)

How many wires does the alternator have? and what make is it?, and the make of the voltage regulator too, the oil pressure gauge and sender, is it electrical or does it have an oil pressure line coming from the engine to the gauge?.

Could you attach a photo of the oil pressure sender?.


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## Windy99 (9 mo ago)

The make of alternator is a Delco Remy. I believe it is considered a single wire unit. One side which is BATT goes to Ammperes gauge and other side is ground with 2 clip wires in the middle. Could not find make on the voltage regulator but it is a gray square box with wires coming out the top of it. Will include pictures. Right now if I hook up the wire from the OP switch to the Ammperes gauge the battery wires heat up and if I touch the neg. to the battery post it trys to crank but last time it sounds like my solenoid won't kick over correctly.! The Oil Pressure Switch Red (first wire) wire runs into a connector which has a wire going to the voltage regulator on top and one wire to the solenoid and alternator on bottom. The las picture is the top of the voltage regulator.


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## FredM (Nov 18, 2015)

Windy99 said:


> Oil Pressure Switch Red (first wire) wire runs into a connector which has a wire going to the voltage regulator on top and one wire to the solenoid and alternator on bottom. The last picture is the top of the voltage regulator.


I feel that who ever wired this tractor have tried to use the oil pressure sender as a voltage breaker from solenoid to voltage regulator, that is what the safety switch and ignition switch are for, your first photo shows an oil pressure line going to the oil pressure gauge, so the oil pressure gauge is worked by the oil pressure line, you will need to think about disconnecting the wire feeds to that oil pressure sender as these are a gerrymander, it is obvious that your tractor has oil pressure gauge reading by pipe pressure, not wire.

Your ignition switch should be a 3 wire switch, which should have the power supply from heavy solenoid connection,(battery positive), a run connector (gauges etc.), and the start wire that goes to the solenoid start connector, you will need to trace these out, "somewhere in the gerrymander you have a short", and "a direct hot wire to the solenoid" which is causing the starter to run as you describe, so this side of things are not wired correctly either.

The alternator is a 4 wire, the heavy connection should be battery, one of the smaller wires in the double connector is field and the other is usually for the warning light, we will have to talk about the battery warning light wire a little later, and the other wire is for ground, can you tell me the make of the regulator and the wire tab markings in order.

I am going to have a fiddle with your wiring diagram and see if I can improve it a little for you.


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## Windy99 (9 mo ago)

Please be aware that I am located in the USA so my Massey is a USA brand. I took the hood or bonnet as you would say off again to be able to trace all wires. First off, the ignition switch is a 2 prong switch which is for Diesel models. Three prong is for Gas models. My Massey is a Diesel 175. In tracing the wires I finally found the neutral switch behind the fuel filter on engine. I took the voltage regulator off but there is no brand or number except 7708 on side of metal frame which means nothing as far as I can tell. The number for the regulator is #1031060m91. I hope the no. helps you somehow. When I looked at the back side of regulator the place for the light wire looked to be burnt which is why I guess they cut ALL light wires off and there are no wires to light switch to be found! . I traced ALL the wires and this I what I found:
1)Ignition Switch- Red wire to safety switch (first prong) and Green wire to amperes gauge (amp meter) (this wire was bound together at factory with Red wire that goes to (Battery) post on Alternator.
2)Safety Switch- Green wire from ignition and Black wire to Right side of solenoid.
3)VOLTAGE REGULATOR- Green wire to alternator Left plug
Red wire- goes to a connector (with 2 wires on top and 2 on bottom) the other wire on top goes to the Oil Pressure switch-the wires on bottom go to Alternator plug and the solenoid screw.
Green Wire- goes to lights which was hooked up to amp meter gauge but I took it off! cause it went to no where.
Red Wire- goes to fuel gauge right screw post

Gauge Wiring- Fuel Gauge- Black wire from gas tank to left screw, Red wire Right screw to voltage regulator
Amperes Gauge- (left screw post) Red and Green wire(bound together to alternator and ignition switch) and Red wire to oil pressure switch(which has the connector and the 2 wires at top and bottom), (right screw post) Black wire to solenoid attached to battery cable post with batty. cable.
Tachometer-Cable to alternator
Oil Gauge- nothing hooked up to screw post
Oil Gauge Pressure Switch- (right flat post) Red wire to voltage regulator that splits with connector. (left flat post) Red wire to amperes left screw post.

pictures are not in the order i put them LOL I hope this helps and doesn't confuse to much. I really appreciate ALL your help on this.


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## Fedup (Feb 25, 2014)

My advice would be start with the proper wiring diagram. The one you posted has no bearing on your tractor. It clearly shows a generator, an electric oil pressure gauge and tachometer, none of which you have.

Yours is a standard (except for the tach drive) Delco externally regulated alternator. Commonly used during the late 1960's and early 1970's on many tractors, cars and trucks. Your oil pressure switch is a generic replacement for the factory switch which had only two terminals. The original circuit used the pressure switch to supply power to excite the charging system, and that's about it. Gauges where all mechanical, except for the fuel gauge, which was powered from pin 4 on the regulator. That pin supplied battery voltage only when the system was charging. I believe one side of the pressure switch connected to the ammeter, the other went to either pin 2 or 3 on the regulator. Not sure which any more. The key switch is merely a glorified starter switch, nothing more. You start the engine, oil pressure closes the pressure switch. That excites the charging system, once charging the fuel gauge comes on. When the engine stops, all that turns off. Simple as that. 

I have neither the proper diagram for you nor the skills to post it, but that's where you need go next. Perhaps someone here can find and post that for you.

Once past that, the rest of your wiring should be pretty simple. However ratty the condition, and whatever has been done or changed over time you should be able to sort it out. The lights and flashers were always battery live, and had nothing to do with the pressure switch related circuits.


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## Hacke (Feb 22, 2011)

Fedup said:


> My advice would be start with the proper wiring diagram. The one you posted has no bearing on your tractor. It clearly shows a generator, an electric oil pressure gauge and tachometer, none of which you have.
> 
> Yours is a standard (except for the tach drive) Delco externally regulated alternator. Commonly used during the late 1960's and early 1970's on many tractors, cars and trucks. Your oil pressure switch is a generic replacement for the factory switch which had only two terminals. The original circuit used the pressure switch to supply power to excite the charging system, and that's about it. Gauges where all mechanical, except for the fuel gauge, which was powered from pin 4 on the regulator. That pin supplied battery voltage only when the system was charging. I believe one side of the pressure switch connected to the ammeter, the other went to either pin 2 or 3 on the regulator. Not sure which any more. The key switch is merely a glorified starter switch, nothing more. You start the engine, oil pressure closes the pressure switch. That excites the charging system, once charging the fuel gauge comes on. When the engine stops, all that turns off. Simple as that.
> 
> ...


I do not know if I help or add confusion to this, but I got interested in the oil pressure switch function and looked at a wiring diagram for 135-165. I can not find anything about 175, but it might work ("Other later models are similar"). The generator setup is the same as in Windy99´s diagram.

The oil pressure switch is only for the generator setup in these diagrams. Is it possible to change the wiring according to the alternator setup in the attached diagram, and omit the oil pressure switch?


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## Fedup (Feb 25, 2014)

Eliminating the pressure switch is possible yes, but it's main purpose is to energize the alternator (and as such the fuel gauge), so that would require an alternative means of doing that. It's there now, so if it works, keep it. 

Personally, I don't fool with the externally regulated alternators any more. If they work, fine, but when they don't I switch to an internally regulated 10SI type, and match the wiring to that, whatever that takes. The old style are much harder to come by, and the external regulators sold today are typical "aftermarket replacement" items and often don't work right out the box. 

Just guessing here, but this one probably doesn't work at present, and that's part of what this thread is all about.


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## Windy99 (9 mo ago)

Fedup said:


> My advice would be start with the proper wiring diagram. The one you posted has no bearing on your tractor. It clearly shows a generator, an electric oil pressure gauge and tachometer, none of which you have.
> 
> Yours is a standard (except for the tach drive) Delco externally regulated alternator. Commonly used during the late 1960's and early 1970's on many tractors, cars and trucks. Your oil pressure switch is a generic replacement for the factory switch which had only two terminals. The original circuit used the pressure switch to supply power to excite the charging system, and that's about it. Gauges where all mechanical, except for the fuel gauge, which was powered from pin 4 on the regulator. That pin supplied battery voltage only when the system was charging. I believe one side of the pressure switch connected to the ammeter, the other went to either pin 2 or 3 on the regulator. Not sure which any more. The key switch is merely a glorified starter switch, nothing more. You start the engine, oil pressure closes the pressure switch. That excites the charging system, once charging the fuel gauge comes on. When the engine stops, all that turns off. Simple as that.
> 
> ...





Fedup said:


> My advice would be start with the proper wiring diagram. The one you posted has no bearing on your tractor. It clearly shows a generator, an electric oil pressure gauge and tachometer, none of which you have.
> 
> Yours is a standard (except for the tach drive) Delco externally regulated alternator. Commonly used during the late 1960's and early 1970's on many tractors, cars and trucks. Your oil pressure switch is a generic replacement for the factory switch which had only two terminals. The original circuit used the pressure switch to supply power to excite the charging system, and that's about it. Gauges where all mechanical, except for the fuel gauge, which was powered from pin 4 on the regulator. That pin supplied battery voltage only when the system was charging. I believe one side of the pressure switch connected to the ammeter, the other went to either pin 2 or 3 on the regulator. Not sure which any more. The key switch is merely a glorified starter switch, nothing more. You start the engine, oil pressure closes the pressure switch. That excites the charging system, once charging the fuel gauge comes on. When the engine stops, all that turns off. Simple as that.
> 
> ...


There is No wiring diagram to be found which is why I am seeking help. Thanks for all your help.


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## Fedup (Feb 25, 2014)

Okay, I see where you're coming from. 

Check your PM inbox.


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## Windy99 (9 mo ago)

Fedup said:


> Okay, I see where you're coming from.
> 
> Check your PM inbox.


Could my pressure switch be bad? Should I have continuity on both copper flat post of OP Switch?


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## helpmethispieceof (9 mo ago)

hey just curious im also trying to get to my instrument pannel but i cant because the fueltank is in my way how do you remove it? mf 220 
or did u not have a fuel tank








closet to ur steer wheel


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## Fedup (Feb 25, 2014)

The 220 is a totally different tractor. You will probably need to remove the fuel tank.


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