312-8 1991 model Confusing Key Switch Wiring, Please Help!

[Lefty 57 54]

Hello, I am a new Wheel Horse 312-8 owner. I am also still a newbie here in the forums, although I have read many posts and learnt a great deal from fellow Wheel Horse owners.  I am over the big pond as I live in Oxfordshire in the UK.

I am having a puzzling time whilst replacing the Ignition key switch on my 1991 model 312-8. I am replacing the original very corroded key switch part number #111215 with a Toro replacement part number #103991, both switches have a 5 pin black plastic connector block and a single white plastic ground lead attachment to the six pins on the back of these key switches. On looking at the wiring diagram in the "Demistify" PDF download, page number 378 for my 312-8 1991 model it shows the following connections at the key switch terminals:

 

S-Tan wire to Solenoid/Starter

B- Red wire to Battery

A- White wire to Accessories? ( I thought the white wire goes to the Regulator, so should the white wire not go to the key switch terminal marked R ?)

M- Dark Blue wire to Magneto

R- Pink wire to regulator? ( I thought the pink wire goes to the accessories, so should the pink wire not go to the key switch terminal marked A?)

G-Black wire to ground/earth. ( This is the separate white socket that has the black earth wire.)

 

I have looked at the wiring diagram and also lots of posts here in the Electrical issues section. I found a post entitled "Where is the mistake" which describes a wiring diagram error on the Magnum 300 series engines just like mine. Please can somebody clarify exactly where the pink and white wires go to on the key switch on a 1991 model 312-8 model number R112K803. My aching brain is just telling me to switch the two wires over. White to terminal R and pink to terminal A. Is the wiring diagram correct? Or am I correct, please can somebody here help?

 

Edited August 30, 2020 by Lefty 57
grammar correction

[gwest_ca-(File Mod) 10,478]

I'm with you on this one. I think the diagrams are wrong.

The G, M and A are shorted to Ground when turned off.

If the white (Rectifier) went to the A and when turned off if the A (Rectifier output now) happened to make with the M terminal before being grounded the ignition coil is toast.

 

Garry

[953 nut 51,511]

1 hour ago, gwest_ca said:

If the white (Rectifier) went to the A and when turned off if the A (Rectifier output now) happened to make with the M terminal before being grounded the ignition coil is toast.

Garry, I have not tested this but it is my understanding that these switches are a "Break Before Make" switch where there is a null zone where nothing is connected momentarily while the switch positions are changed. 

[Lefty 57 54]

Okay here is an update on my progress so far. When I bought the 312-8 the only way to start it was by shorting across the two top pins of the Solenoid. When I removed the battery to put it on charge I noticed the rear pin/connectors from the original #111215 key switch were very corroded and decided a new replacement Toro #103991 (33-394) key switch would maybe solve the starting issues. I have also put a new solenoid onto the Wheel horse. 

When I removed the original 5 pin black plastic lead plug from the rear of the key switch, I popped each female spade terminal out of the plastic plug to clean them. I also cleaned the corrosion of the original key switch male spade terminals so that I could identify each terminal. The original wiring in the 5 pin connector was indeed wired up follows:

 

S-Tan wire to Solenoid/Starter

B- Red wire to Battery

A- White wire to Accessories!!!!

M- Dark Blue wire to Magneto

R- Pink wire to regulator!!!!

G-Black wire to ground/earth. 

I re-positioned the white wire and the pink wire female terminals in the 5 pin block, so that the white wire would attach at the R (Regulator) male spade post of the new key switch and the pink wire would now attach at the A (Accessories) male spade post. 

I replaced the battery and tried starting the 312-8 with the new key switch. With the key in the "on" position the idiot warning lights would all come on when the test button was pressed. I sat in the seat with left foot down on the clutch, right foot down on the brake pedal. PTO lever was in the disengage position, gear stick in the neutral position and I tried turning the key to start.......Nothing, except that when I let go of the key and it returned to the "on" position I heard the solenoid click. I tried a few times and only got the solenoid clicking as the key moved back to "on". I decided to start the engine by shorting across the two top pins of the solenoid as I had given the Carburetor and the fuel pump a thorough cleaning. The engine fired up almost instantly with very little choke and ran beautifully, no smoke or knocks. It obviously was happy that I had changed the engine oil and cleaned the breather mesh whilst the carburetor was off the engine.

I let the engine run for about 5 minutes just so that it warmed up a little and then I turned the key to "off"......Nothing the engine kept running!. I got of the seat thinking the seat switch would shut down the engine, No it continued to run! I turned the fuel tap to off at the tank but it still kept running, there must be quite a bit of fuel in the Carburetor fuel bowl. In the end I got a pair of pliers and unplugged the Spark plug lead. Result, engine off. 

So I am puzzled, do I switch the pink and white wires back to their original positions, pink to R terminal and white to A terminal?

I am confused because some of the wiring diagrams I have down loaded here for the 1991 312-8 classic with a Magnum engine, do show that the pink wire goes to A (Accessories) and the white wire goes to R (Regulator) on the key switch and yet when I looked in the " Demistify " PDF download, page number 378 for my 312-8 it shows them wired up just as I found them in the original Key switch?.

Sorry for such a long post. Garry if you read this please can you offer some advice as I have read many of your forum posts and you seem to be the man for all things electrical.

I love working on my wheel Horse and one day hopefully I will get it to start again with the Key. Today I cleaned as many of the earth points as I could find and also added an additional earth lead to the back of the Hours/Volts gauges, key switch, metal panel.

 

[midpack 804]

Do you know if the "low oil" sending unit is working? I had to take that out of the equation for the Magnum 12 I put in a C series machine to start with the switch. 

 

I forget exactly what I did to test it, but if I remember right, I pulled the connecting wire from the plug and taped it off. I check the oil level each time I run a machine, so I don't need a low oil switch

[Lefty 57 54]

Hi there Midpack,Thank you for your message. I am waiting for a new test light to arrive so that I can work my way around the various circuits. I do not know if the "low oil" sender unit is working for sure. When I press the idiot lights test switch the red "low oil" LED lights up as it should along with all the others and when the engine is running the light stays off. I will test it though.  I have just given the engine an oil change so I know the oil level is good. Just need to work out the correct wiring on my key switch as two wires have got me puzzled. I will have to work my way through each safety switch, the relay and fuse box to track down my starting issue. I like a challenge and this old 312-8 is definitely that! The engine sounds great and it has some serious power. Electrics are not my favorite but I am trying to get everything working as it should before I start restoring the paint work. It's definitely keeping me busy! I did buy it as a project as I think these old Wheel Horse garden tractors are really well made and worth saving.

[gwest_ca-(File Mod) 10,478]

There are special instructions for removing the low oil switch without damaging it. They are no longer available. Not suggesting you remove it - just making you aware of it.

Sounds like your wiring was originally just as some diagrams suggest. When I originally asked the question I had found both versions plus some were drawn one way and labelled the other way.

Looked at a 1990 model today and a white wire goes to the Accessory terminal so matches what you have. The R terminal has an orange wire which does not match the diagrams and I did not want to dismantle the gentleman's tractor to find out where it went.

Looks like I have some diagrams to correct.

 

When you try to start does one or more of the idiot lights come on?

 

Garry

[953 nut 51,511]

I couldn't find a 1991 drawing so used the '92-93. I know that you have looked at all of these before, but lets give it another shot.

First lets take a look at your solenoid. Is one of the small posts on your new solenoid grounded?  With the transmission in neutral, have you run a small jumper wire from the battery (+) to the terminal with the light blue wire going to it? If the solenoid works with the jumper we will back-track from there. 

If this ignition switch were in the OFF position the Dark Blue wire which is on the "M" terminal would be grounded by the switch. With the PTO engaged and the seat relay de-energized (no one in the seat) the dark blue wire would go to ground. If the relay isn't working or the seat switch isn't opening the PTO switck won't kil the engine.

[Lefty 57 54]

Many thanks for replying to my posts. Garry I will double check the idiot lights and get back to you. I know they all light up when you press test. I never noticed any lights coming on whilst engine running but I will check again. Especially when I try to start the engine. 

Thank you 953 nut for taking the time to help me with my starting issue. I managed to find a wiring diagram for my 1991 model 312-8 looking at the starter motor circuit I have different wires running to the solenoid. On the two large top posts I have a thick black lead running to the Starter motor and on the other top post I have a thick red + lead running from the battery there is also a thin red wire that comes from the 25v fuse box housing connected to the same post. On the two lower spade connectors on the solenoid, yes one is grounded as it has two black wires running to one of the spades, the other wire is not light blue its a purple wire. I will do as you suggest 953 nut and try a jumper lead to the purple wire to see if the solenoid works. It should do as its brand new but I will test it. 

953 nut you posted:

"If this ignition switch were in the OFF position the Dark Blue wire which is on the "M" terminal would be grounded by the switch. With the PTO engaged and the seat relay de-energized (no one in the seat) the dark blue wire would go to ground. If the relay isn't working or the seat switch isn't opening the PTO switch won't kil the engine."

 

 I remember when the engine was last running and I turned the key to off it kept running, I did try lowering the engine speed and then engaging the PTO lever as I thought the load at low revs may stall the engine but it did not it just kept running. When I got off the seat to pull the plug lead the PTO lever was in the disengage position so the seat switch would have had no effect is my understanding. I understand that the dark blue wire M (Magneto) should be grounded when key is in off position.  I will have to check the seat switch when my new test light arrives along with the PTO switches.  Thanks again so much for your help and advice. 

 

 

[Lefty 57 54]

Well today the weather has stopped work on my 312-8 and its starting issue. It has been a very grey, dull, wet day here in the UK. 

My Wheel Horse has remained under its rain cover. Although I did manage to make up a couple of extra earthing leads, whilst out in my garden shed. I have put the battery on slow charge ready for my next "starting with the key attempt". I am going to switch the pink and white wires that go to the key switch back to their original positions in the black plastic 5 pin plug. Pink to R and white to A. I will also add an additional ground lead to the casing of the key switch. 

When the engine was last running the key in the off position failed to stop it running. Which makes me think the key switch was not grounded properly. I am going to loosen the mounting bolt that holds the key switch to the metal panel with the hours and volts gauges, and then attach the new ground lead at the rear of the key switch, locking it tight and attaching the ground to a bolt in the battery housing. That will give me two additional grounds on the metal panel holding the key switch. I have been studying the wiring diagrams here for my 1991 model 312-8 and as soon as the weather allows I will begin testing out the various connections and switches on the starting circuit. I will update you very helpful people here as soon as I track down where the fault is, if I can find it!. Or I may return for more advice once again. 

[Lefty 57 54]

STARTING WITH THE KEY ATTEMPT THREE:

Success it started first attempt at turning the key!

The extra ground lead onto the metal panel that holds the key switch and gauges seems to have sorted the fault. Whilst I was cleaning all the electrical connections I could find, I did notice the the bolt from the starter motor which has the lead from the solenoid attached to it was very loose when I took of the lead. Its the nut nearest to starter motor which was loose. I tightened the nut which made the bolt secure again and then re attached the thick cable from the solenoid.

Either the poor earth on the key switch panel or the loose securing nut on the starter motor caused my no start with key issue.

When I sat on my 312-8 and turned the key to run I noticed the voltmeter sprang into life, reading about 13 v and in the green zone. I also had a red LED warning light on the idiot panel. It was the "Parking Brake" warning light. I pressed test and all the LEDs lit up with the "low oil" light flashing which I believe is normal. When I let go of test I still had the "Parking Brake" LED on.

I tried the parking brake by pushing my foot down on the brake pedal, I could move the parking brake lever 3/4 of the way back and it engaged so that when I took my foot off the brake pedal the pedal remained down and the lever stayed put. I then pushed on the brake pedal again and the parking brake lever disengaged and moved forward. I think this is normal. Please correct me if I am wrong as this is my first Wheel Horse. Does anyone know why the Parking Brake light stays on when the ignition key is in the "Run" position? Is this normal? or is it indicating a fault somewhere?

 

[Lefty 57 54]

Well today I did some more work on my 312-8. On investigating why I have the "Parking Brake" LED lit up when I turn the key to run. I found a white and a pink wire running to a switch below the parking brake lever. I can see it through the transmission gear levers panel but cannot really get to it unless I remove the 4 screws holding the panel. I have tried a number of times to shift those screws but they are rusted solid. I have sprayed WD 40 under the panel at the screws and hopefully tomorrow they might budge. If all else fails I do have some drill attachments that chew into rusty screws and that usually works.

I am trying to save as many original parts as possible but sometimes new bolts and screws are a must.  

These Wheel Horse garden tractors are really well made and engineered to last.

Every day when I am working on my 312-8 I find things that show the quality of these little tractors. Whilst I was working my way through the wiring, cleaning connections and grounds. I noticed that the rear lights were not working. Not really important I know but I want everything to be working as it was intended to during my restoration of "Little Red". Anyway I removed the rear light covers and they were both full of old dead moss!

I removed the little push in light bulbs and examined them, neither was blown and both cleaned up okay. I cleaned and removed all the old moss and then tested the wiring running into each light with my test light. I found I had intermittent power coming into the bulb housing but each lead had a build up of moss and crud where the lead meets a tiny washer and the metal connector plate held on a white plastic post. I used one of my wives sewing needles to clean between the metalwork connections. I pushed both little bulbs into their white rubber housings and flicked the lights switch with ignition in on position and "Both"  the rear lights worked. 

Little by little each day my Wheel Horse is coming back to life. It maybe 29 years old but it really is a quality machine. I have wanted my own Wheel Horse for a very long time and was lucky to find and

win mine recently on  Please can someone advise me of the correct place to put my various posts.  As I repair and restore my 1991 312-8 and its 36" mowing deck back into hopefully full working order. There are bound to be more posts and enquiries from me as I resolve each issue or come across problems and figure out how to repair things.  Maybe some of my posts will help others here. I am new to this forum but I myself rely on the various posts and free downloads I find here to guide me in getting "Little Red" back into shape. In fact it was knowing this forum existed that finally made me go and find my own vintage Wheel Horse.

[midpack 804]

I've had good luck getting the screws you're having trouble with out with a hand held impact wrench. make sure you have the right size Phillips bit too

[953 nut 51,511]

On 9/6/2020 at 2:25 PM, Lefty 57 said:

 Please can someone advise me of the correct place to put my various posts.

At the upper right corner of the home page you will see the word CREATE, click on it and a drop down will appear, select TOPIC and another drop down will appear with several topics to choose from.

[Lefty 57 54]

Many thanks 953 nut, that is exactly what I needed to know. I'm still working my way around this great forum. 

Lefty 57 (Paul)