Ford 9N generator pegging positive after cleaning connections

[EddieS]

Hi everyone,

I have a 1942 Ford 9N that my grandfather bought new and was later restored by my dad and uncle. The tractor is still 6V positive ground, and when my dad restored it, he put a 3 terminal generator on it and an actual voltage regulator. I am now the third generation owner, and it still runs great.

A few weeks back I decided to clean the connections on the generator and regulator, so I removed each connection one at a time, used a brass brush to clean the terminal and crimp connectors and then reinstall and tighten. When I started the tractor up, immediately the ammeter pegged positive at 30 A. Thankfully I saw it within 10 seconds or so and shut the tractor off. I smelled a little electrical burning smell, but it wasn’t bad. I ran out of time, so I just disconnected the generator wires and put the tractor away. What did I do wrong, or what has gone wrong, and how can I fix it? Thank you for your help in advance!

Eddie

 

[Jim L WA]

Look for any of the connections touching one another or making contact with what looks like a grounded plate that runs under the other three connections at the regulator. You can look for any frayed wires that may be contacting ground.
What caused you to clean the terminals in the first place. Was it acting up? or they just looked like they needed it?

 

[EddieS]

Thanks Jim, will do! Yep, they just looked like they were dirty and hadn't been cleaned in many years. Now I'm wishing I wouldn't have... I don't think I overtightened the connections at the generator, but I definitely tightened them tighter than they were before. Do you think I would have shorted something inside the generator?

 

[Mad Farmer]

Any chance you switched/mixed up wires to voltage regulator? Quick check the wiring diagram.

I don't see the wires color coded in the posted picture.

 

[Ray,IN]

Retrace your actions-slowly. I suspect mad farmer is right. You did take pictures of the wiring before disconnecting anything, right? It can't be a direct short or you would know very soon. I know pictures have saved me several times..

 

[Ericp351]

Above, and do a re poliziation, mistake, fixed, in wires or not.

 

[Dave G9N]

I would agree with polarization. No direct experience, but I've seen the advice from the old forum gurus often enough.

That looks like an 8N10000B generator, which was apparently not unusual to find installed on 9N and 2N tractors. See figure 15 of Tim Daley's history of the 9N tractor generator. Assuming the pdf opens there are instructions for polarizing generators.

 

[EddieS]

Great, thanks everyone. I will start by re-tracing my steps and measuring continuity to see if there are any shorts. I can't believe I hooked up any of the wires wrong, because I took them off only one at a time, cleaned and re-installed. If I don't find any shorts, then I'll try the re-polarization of the generator.

Quick question - this is more of a theoretical question, but why did Ford put a third terminal on the generator if it's just connected to ground? Why couldn't they get just ground through the chassis and save a third connection?

 

[Jim.ME]

My thoughts. You say it pegs the needle positive which indicates it was charging in the correct direction, I don't see what polarizing it will accomplish. Polarizing gets the current flow in the correct direction, it is there already.

Going by your saying you did the wires one at a time it would be hard to mix them up. I expect in undoing the wires you disturbed something and have created a short or ground somewhere by a stud turning inside the generator or broke something loose in the regular from twist on the terminals.

Edited spelling

 

[EddieS]

I agree with all your thoughts, Jim - thanks. I hope to get started working on it again this weekend when the weather warms up. Will give you guys updates when I know more!

 

[EddieS]

Hi everyone,

Update is this - I had a little time yesterday, so I measured the DC resistance of all terminals on the generator and the regulator. All measured 0 ohms to ground (a short), except for the middle terminal on the regulator which measured 10 ohms. Despite that, I hooked up all the connections to the generator again, started the tractor, and it still pegs the ammeter positive at 30 amps. So then, I unhooked just the one connection to the FIELD terminal on the generator and started the tractor - it still pegs the ammeter positive at 30 amps. This makes me think that there must be a short on the FIELD terminal inside the generator, if it's disconnected from the regulator and still outputs the max amperage. What do you think?

 

[Btzj02]

When using an Ohm meter to test for resistance while the equipment, generator, is still attached to the tractor may give misleading results. Attached is a shop manual page indicating how to check for Resistance using a voltmeter. Please note the highlighted section on high charging rate.

 

[Jim L WA]

Hi everyone,

Update is this - I had a little time yesterday, so I measured the DC resistance of all terminals on the generator and the regulator. All measured 0 ohms to ground (a short), except for the middle terminal on the regulator which measured 10 ohms. Despite that, I hooked up all the connections to the generator again, started the tractor, and it still pegs the ammeter positive at 30 amps. So then, I unhooked just the one connection to the FIELD terminal on the generator and started the tractor - it still pegs the ammeter positive at 30 amps. This makes me think that there must be a short on the FIELD terminal inside the generator, if it's disconnected from the regulator and still outputs the max amperage. What do you think?

EddieS: Using your ohm meter, if you see that that Field terminal is grounded with the wire removed, then I think you are right. It must have gotten shorted to the housing while you were working on it.

 

[EddieS]

Great, thanks Jim! Yes, I will try what Btzj02 has above, but I think I will need to take the back cover off the generator and see what has happened. Anybody have any thoughts or tips or things I should be aware of when I do that? Thanks again for all the help.

Eddie

 

[Btzj02]

Be careful when you pull off the cover. When I rebuilt mine the wires were very short and easy to do some damage.

 

[showcrop]

Whenever I am tightening a screw or nut on a terminal I hold the terminal while turning to reduce the chance of turning a stud.

 

[EddieS]

Yep, I try to do that too - and my Dad always told me the same thing I guess I didn't do a good enough job on that this time... dang it. Will be a couple weeks before I can get out to the farm again and work on it, but I'll keep you guys updated when I do. I'm just a little worried about taking the back cover off the generator - don't think it's ever been off. Seems like some brushes or springs could snap out of place, and I'd have no idea how to get it back together. Any other tips or warnings on that would be greatly appreciated!

Eddie

 

[HCooke]

Yep, I try to do that too - and my Dad always told me the same thing I guess I didn't do a good enough job on that this time... dang it. Will be a couple weeks before I can get out to the farm again and work on it, but I'll keep you guys updated when I do. I'm just a little worried about taking the back cover off the generator - don't think it's ever been off. Seems like some brushes or springs could snap out of place, and I'd have no idea how to get it back together. Any other tips or warnings on that would be greatly appreciated!

Eddie

I would take the generator and the VR to a repair shop.

 

[Btzj02]

I would recommend doing one more test before removing the generator. I suggest this because normally if the field coil is grounded the magnetic field would collapse and you would expect the amperage output to go down not up or, be low and very erratic.

Test1: Lift both the field wire and the output wire at the generator but leave it grounded. Start the tractor and measure the voltage on the output terminal and the field terminal.

Test2: Reconnect the field coil wire and restart the tractor and again measure the voltage on the output terminal and the field coil connection.

If the field coil was grounded test 1 should read zero on the field coil terminal and possibly zero or very low on the output terminal. If the field coil is not grounded you will get a voltage reading on both the field coil and the output due to residual magnetism.
In test 2 if the field coil is grounded the voltage will be very low and the wire may start to warm and the voltage on the output terminal would be low and erratic.

Incidentally regarding your question about, why the ground? All alternators have a ground terminal also and it is usually not used but it is recommended to guarantee a good ground.

 

[Btzj02]