900 Series Electrical issue

btarl63

New User
I've got a 900 series with a serious electrical problem. I'm sure I have a ground somewhere, but I'm having trouble figuring out the wiring.

My tractor has an ammeter. It does NOT have a Voltage Regulator, but does have a resistor block.

I've tried to compare the wiring to the diagrams in the 900 series repair manual, and it looks like it's a combination of the 6 and 12 volt system. Perhaps a conversion?

At any rate, I thought I had fixed an original problem by replacing the key switch. Originally, with the key on, I got 12 V at the Starter motor relay, but only 4 volts at the starter switch. Cycling the key switch, eventually 12 volts would show up at the starter switch, and I could start the tractor.

Now, with the key switch off, I get 12 volts at the starter relay. Key switch on, 2 volts.

Starter motor relay has 4 terminals. Battery, starter, starter switch, and key switch.

Does anyone have a wiring diagram that this looks like? It's not the standard 12 volt (no lights) nor the standard 6 volt (no regulator). It does have a resistor block. Any help would be appreciated.
 

Welcome to the forum!

It has to have a voltage regulator somewhere. Original would have been on the steering column up under the instrument panel.

If it has an alternator conversion, the VR is likely internal to the alternator.

Check all battery connections. They could be dirty or loose. Check other wiring connections. If all connections are tight and clean, suspect an alternator or generator with a dead short. If this were the case, whichever you have should be smoking in short order with power applied.
 
Sounds like you have a bad ignition switch that works when ever it wants to and that can cause major problems. Tractor wiring is so simple that it is not at all hard to rewire one. Shoot I can rewire one in my sleep but I have also rewired many from the ground up. You have a simple ignition circuit a simple start circuit and a simple charging system which all work together to make your tractor run and charge and start
 
Are you sure about the model of the tractor?
900 series originally had a three terminal solenoid.
901 series had a four terminal if memory serves.
The wiring wasn't all that much different but not exactly the
same either. The idiot lights on the dash of the 901 for example.
900 didn't have any idiot lights.
Anyway, the wiring diagram for a 901 maybe the one you want.
 
Yeah, this is a 900. Serial number 960-127825.

Trust me, this tractor has some serious Redneck engineering.

I started lifting leads and checking voltages. As I lifted leads, the voltage at the start switch would go from 2 volts to 12 volts. I traced a 1 ohm to ground to the distributor. There are two leads going to the distributor. One from the coil, and one that runs back to the Keyed switch. This one has the ground. I took the distributor apart, and discovered that instead of points and a condenser, this thing has a solid state ignition. Red and black lead. Black lead goes to the coil, Red lead back up to the switch. Red lead has 1 ohm to metal plate it's attached to. I'll try and take a picture of it.
 
Too bad it couldn't be as simple as getting a different diagram.

The four terminal solenoid will work, key switch provides power
to one side of the actuating coil and the bush button neutral
safety switch provides ground to the other. The engine can't be
rolled over with the starter unless the key is on. Some see
this as a benefit.

EI is a pretty common swap too. Lots of posts on those here.
 
(quoted from post at 15:55:49 01/02/17) Yeah, this is a 900. Serial number 960-127825.

Trust me, this tractor has some serious Redneck engineering.

I started lifting leads and checking voltages. As I lifted leads, the voltage at the start switch would go from 2 volts to 12 volts. I traced a 1 ohm to ground to the distributor. There are two leads going to the distributor. One from the coil, and one that runs back to the Keyed switch. This one has the ground. I took the distributor apart, and discovered that instead of points and a condenser, this thing has a solid state ignition. Red and black lead. Black lead goes to the coil, Red lead back up to the switch. Red lead has 1 ohm to metal plate it's attached to. I'll try and take a picture of it.
ne Ohm sounds too low, but there will be something other than an open circuit, since the EI module will need some power.
 
Yeah, I've actually found the solid state upgrade here on this site's store. Same manufacturer. I looked up some of the specs on it, and 1.4 ohms seems right. So I'm gonna move on from there.

So I'm reverting to my Navy troubleshooting training.

I know the last thing I did was replace the key switch. I've checked it mounted, unmounted, and even put the old one back on. Same thing.

I KNOW the tractor works as wired. So now I'm going to Easter egg it.

I'm pulling the starter solenoid, and will replace it. But in doing so, I tried to disconnect the cable from the starter first, since it's hard as hell to get to it on the side of the solenoid. Should have sprayed some liquid wrench first. I've sheared the connector bolt. Luckily, it appears this is a common occurrence, as I have found a Starter Terminal Repair stud.

Anyway, I'll be ordering it and a new Starter Solenoid in a couple of days. I'll post my results.
 
Here is what I have traced out as a wiring diagram:

view
 
if the stud turned int he starter, you may be in for some more work, if just the external stud was damaged, the repair stud MAY
or may not work, depending on if it has something to thread on to.

Post back.
 

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