Off color MM UB diesel electrical?
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=210718
Printed Date: 12 Apr 2026 at 8:48pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Off color MM UB diesel electrical?
Posted By: grinder220
Subject: Off color MM UB diesel electrical?
Date Posted: 12 Apr 2026 at 8:50am
| I need some help figuring out the correct way to wire the light switch up. When I bought the tractor the original switch was missing one wire,seized up and broken at one terminal. Its a 3 position push/pull switch with built in resistor very similar to what a WD-WD45 uses to control the charging system. Actually the aftermarket POS Chinese switch is the same between the 2. Anyways the wire frome the resistor was missing on the original switch, one terminal went to the fuse/lights the other to the voltage regulator. Should the wire from the resistor go to the load side of the amp gauge? There is no wiring diagram in the operators, parts or repair manual for this tractor and I can't find anything online. There's online diagrams for the gas tractors but they use a completely different style of switch as that switch also controls the ignition system. |
Replies:
Posted By: steve(ill)
Date Posted: 12 Apr 2026 at 9:39am
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first of all i know NOTHING about your MM.... second, the RESISTOR on the light switch was VERY COMMON 70 years ago on 6 volt systems WITHOUT a voltage regulator... LIght ON - max charge.. Lights OFF - minimal charge... Very simple.. Years later they changed to voltage regulators on 12 volt systems... and many 6 volt systems were upgraded with a regulator and ELIMINATE the resistor... ---------- if you are 12v.... or 6v with a voltage regulator.. you dont need the resistor... just a simple ON- OFF switch for the headlights.
------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 12 Apr 2026 at 9:43am
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the resistor was feed by the "F" wire from the 6V generator and the other side of the resistor was grounded thru the switch for LO CHARGE.... to get HI CHARGE, the switch bypassed the resistor and Grounded the "F" wire.. ------------- Like them all, but love the "B"s. |
Posted By: Les Kerf
Date Posted: 12 Apr 2026 at 9:47am
I have never so much as touched any M-M. The Allis system uses the resistor to apply either a Full-ground to the generator field (High Charge), or a Partial-ground through the resistor (Low Charge). The resistor is not connected to the ammeter or any other power source. |
grinder220 wrote:Posted By: Les Kerf
Date Posted: 12 Apr 2026 at 9:54am
 Wiring diagram for a typical AC Model CA |
Posted By: TedN
Date Posted: 12 Apr 2026 at 10:06am
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We have a mostly original ZB in my mom's shop. It is similar vintage so the wiring should be the same, I will try to remember to look at it today. Edit - I just reread the original post, our ZB is gas. I will look anyway. Ted ------------- 190XTD seriesIII, 190XTD seriesI, maroon belly 7000, 7045, 190XTD series??? project(or maybe parts) |
Posted By: grinder220
Date Posted: 12 Apr 2026 at 11:04am
It is a factory 12v system. Here is a picture of the new switch and the original for comparison. The charging system was not functioning when i bought it. The regulator was shot,not sure on generator condition yet. So the lights should be connected to the resistor terminal then? What wire goes to the fuse on the switch then? Original has a fuse on the dash like a hundred series allis uses. Does the regulator break connection on its own then the generator stops spinning?  
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Posted By: Les Kerf
Date Posted: 12 Apr 2026 at 1:01pm
Ok, I don't believe that anything Steve and I stated above is applicable to your system. We were both referring to the 6 Volt Allis system that uses a simple cutout relay and has no discrete Voltage Regulator as such.
I truly don't know for certain but I doubt it. If I had it in my hand I would use an ohmmeter to try to determine how the resistor is connected in the switch.
I would expect one end of the fuse to connect to the ammeter and the other end serve the lights
Most "A" circuit regulators apply ground at the regulator, they typically use a built-in resistor and automatically switch back-and-forth between full ground and resistive ground. I have no idea why your system has a separate resistor if it has an actual Voltage regulator
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Posted By: steve(ill)
Date Posted: 12 Apr 2026 at 1:18pm
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it still makes no sense to have the resistor if you have a Voltage Regulator.... Are you looking at a CUTOUT BOX, or a real REGULATOR ? How many terminals does it have going to it ? If the ORIGINAL switch had a resistor... then its possible they did a DELETE and installed a voltage regulator instead... Dont need BOTH.. ------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 12 Apr 2026 at 1:21pm
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unless the resistor is a head light DIMMER.... but i see no need for that.. GOOGLE-----On older Minneapolis Moline tractors with 3-position (Off-Dim-Bright) light switches, the resistor serves two primary functions depending on the switch position: it either dims the lights (usually in the 'D' position) or acts as a generator field resistor to control charge rates in cut-out relay systems.
------------- Like them all, but love the "B"s. |
Posted By: grinder220
Date Posted: 12 Apr 2026 at 1:36pm
It's a regulator not a cut-out,the broken wire shown is for the front right headlight 
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Posted By: grinder220
Date Posted: 12 Apr 2026 at 1:43pm
Here's a picture from the parts book, doesn't state regulator or cutout
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Posted By: Les Kerf
Date Posted: 12 Apr 2026 at 3:42pm
It has multiple wires going to it so it is must be a regulator rather than a cutout. With an actual regulator you definitely do NOT want that resistor connected to anything involving the charging system. As far as dimming your lights, I would leave that alone until you can get it charging properly.
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Posted By: steve(ill)
Date Posted: 12 Apr 2026 at 4:05pm
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Agree... with a voltage regulator, the ONLY THING a resistor on the light switch could be used for would be to Dim the Lights..
if your regulator has 3 terminals ( none on the bottom) then it wires like this.. If the regulator is 20 years old or more, it probably is causing problems with charge.. If you have a 4 terminal regulator ( one on the bottom)... then the "L" terminal on the side can be used to feed the LIGHTS..  ------------- Like them all, but love the "B"s. |
Posted By: grinder220
Date Posted: 12 Apr 2026 at 4:11pm
| Ok, I want to make sure I hook up the switch correctly. The terminal with the fuse would go to the amp gauge,the resistor to the lights and the other to the regulator then, is that correct? |
Posted By: steve(ill)
Date Posted: 12 Apr 2026 at 4:17pm
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i would guess that the OUTLET from the amp meter is the HOT feeding the resistor.... and other OUTLET of the resistor goes to the lights... somehow when you pull the switch to BRIGHT, it bypasses the resistor and puts the amp / power straight to the lights.
You want to make sure that the NEW SWITCH does not GROUND the RESISTOR outlet side to the SWITCH CASE.... thats what MOST of them do when used with the 6V generator. ------------- Like them all, but love the "B"s. |
Posted By: Les Kerf
Date Posted: 12 Apr 2026 at 4:55pm
Yup. If that new switch is indeed identical to an Allis-Chalmers style light switch then the resistor will apply ground and you will let the smoke out of something that you would rather retain un-smoked. I would NOT connect that resistor to ANYTHING for now.
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Posted By: steve(ill)
Date Posted: 12 Apr 2026 at 6:04pm
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Agree... the resistor is Useless.. Forget it... You can use the switch to turn the lights ON and OFF... thats all you need on that end.. For the CHARGE system, follow the drawing above for the regulator / generator.. ------------- Like them all, but love the "B"s. |