Farm Equipment - IB generator diagnosis update

I disassembled and replaced the brushes, bushing bearing, & end cap because 3^rd brush post was bent. I coated the wire from the field coil where it had been rubbing on the commutator.

Reassembled the generator and fired up the tractor. At half-throttle the amp meter went all the way over to full charge of 20 amps. Moving the 3^rd brush didn’t make any difference. Thought perhaps it was the amp gauge so I opened the switch box. I removed the old gauge but discovered that the new gauge I had would not fit in the switch box cover so I reassembled with the old gauge. While attempting to close the switch box the box rubbed through a wire in the harness and shorted out resulting in sparks and smoke. I disconnected the battery, taped up the wire, and reassembled the box. I restarted the tractor and the amp gauge showed 20 amps discharge and the cutout didn’t close.

I removed the generator and disassembled. Tested the system with a multimeter set at 200 ohms. I then reassembled and tested again. Results:

3^rd brush and F terminal – Disassembled 2.2-2.3 ohms Assembled – Same

F terminal to ground (case) – Disassembled – Open Loop (OL) Assembled 3.3 ohms

3^rd brush to ground (case) – Assembled - 0 .3 ohms

Main brush (not the grnd) to ground (case) – 0.3 ohms

“A” terminal to ground (case) – 0.3 ohms

There is no evidence of any damage or deterioration in the circuitry within the generator or the wiring harness other than at the entry to the switch box where I taped it up. There is continuity in the wire from the 3-way “S” terminal to the headlights and taillight. There is also continuity in the wire from the generator Field terminal to the 3-way and in the wire from the “B” terminal on the cutout to the (-) side of the amp gauge. The fuse is good. The resistor reads 3.3 ohms. The switch box has a clean, bright connection to the steering post. Battery reads 6.3 volts.

I opened the switch box and removed the tape from the wiring harness. The shorted wire is the one that connects the cutout battery terminal to the amp gauge (-). This might explain why both the cutout quit working and the gauge shows discharge after the short. ???

Finally, with the switch box still open I ran a jumper from the base of the 3-way switch to the bolt that attaches the box to the steering post. With 3-way switch all the way in and one probe on the end of the “F” terminal wire and the other on the battery + post I got 3.8 ohms. With the switch both halfway and all the way out I got 0.1 ohms.

If anyone sees something that could cause the problem please let me know.

I’m on my way to a electrical repair shop to get a new cutout and have the generator bench tested.

I have converted a few over the years and I like the voltage regulators much better. No more overcharging battery.

steve(ill) wrote:

the short story is there is not a good way to get the generator to put out 20 amps, without GROUNDING the "F" terminal.... that can be internal, the wire to the switch, or the switch itself............. I dont see any other way to do it... but have no explaination of the resistance numbers you measure.

Yup, I'm with you on this Steve, which is why on his previous thread I had suggested that he test the generator by bypassing the stock wiring; he is now going to pay someone to do this for him in their shop. Probably a good plan.

Since everything else seems to be OK and the only thing I didn't check was the armature, I'm thinking that's the cause of the malfunction.

As for the cutout, I know a regulator is a better option and use them on my work tractors but I want to restore the IB to as original as possible. She's going to be a trailer queen. Smile

It probably needs an Arm. It's a common thing. That's why I automatically change them out anytime I rebuild a unit for a customer. I don't get involved with messin' around with a 60+ year old Arm even if it shows good. It's like using a old pair of laces on a new pair of shoes......

For my rebuilds I have my rewinder whittle me a fresh arm so it's like new when done. I have him wind them a little "tighter" as well when he does them, especially the arms for the Starter motors. Gives em' a little more torque especially on the 6V units. Thumbs Up

By the way, I did find an original Duetz-Allis 20 amp ammeter made in the USA.

I'd expect 15 amps when 'fully grounded', 5-8ish when resistor is in series,depending on resistor value.

Old skool idea was gennys don't put a lot out, BUT run all day long, so batteries get fully recharged. If you only do 'short run' operations better to swap over to alternator or put battery charger on tractor every day.

The shop changed the bearing which I had provided, cleaned up the commutator, reset the 3rd brush, and tested another armature I had. Charged me $50. Very willing to answer any questions. Fondy Auto Electric in Fond du Lac, Wis.