Charge Generator

[Ken Hoover]

I have an Autolite GMB 4804B generator that I could not find a replacement or rebuild kit for when I discovered it was not charging the battery. I found a hit that a Prestolite GHD 6001 would fit my tractor, but did not say it would work on my 49 Massey Harris 22. My current gen is positive ground. The replacement I am not sure about, but spins counterclockwise when my original goes clockwise. I was led to believe my old gen was toast because the field and armature showed continuity when fully assembled but so does the brand new gen.
I put the old Autolite back on, and when I connect field to case ground, and armature to gen connection on my relay, I get about 7+ volts which seems right, but the generator gets hot to the touch. Is that normal? I do not recall connecting F to case before, but ammeter is showing 15 Amps at mod RPMs. Trying to preserve the generator since i cannot find a suitable replacement or alternator conversion kit. Any help or confirmation is appreciated. I have a shop book, but the electrical drawing does not clearly show where F is connected since it includes lights, which my tractor never had.

 

[John T]

Ken,

1) To stat with some Masseys used and some Autolite Generators WERE CLASS B CHARGING SYSTEMS..

2) I found this in a previous thread if you need parts

GBM 4804B apparently was originally used on Massey Ponies and VA Cases.
Generator Kit... Wilson # 36-06-9111
Brush Set... Standard Ignition # EX-39
Rear Bushing... Standard Ignition rear bushing # X-4278
Front Bearing... Generic 203 generator/alternator bearing
Lots of auto supply stores sell Standard Ignition, and could order the parts for you, or cross the Standard Ignition #'s over to the brand they handle.
Check out the Wilson site and contact them to find a reseller in your area, if you want to order a kit.

3) With a genny assembled and good brushes intact an ohm meter from any post to case/frame will CORRECTLY register low resistance as the armature is copper wire with one grounded brush, the fields are low resistance, and besides a cheap meter isnt very accurate at low ohm readings.....

4) Ifffffffff its indeed a Class B genny, the fields if good and intact are ALREADY internally grounded...If its a Class B and you ground the external FLD post, you short the field windings out so they cant produce an electromagnetic field as intended !!!!! If its a Class A you do ground the external FLD to full field for max charging BUT NOT CLASS B

5) Unlike a Class A genny, you full field it (yields max charge) by applying battery voltage to the FLD post. On a Class A you full field by grounding the FLD post

6) While sure other methods can work, my method of preference and how I was taught and read over the years and successfully to POLARIZE a Class B Genny was to momentarily flash jump from BAT over to FLD which passes current direct through the fields to their internal ground WITHOUT HAVING TO FLOW THROUGH THE VOLTAGE REGULATOR. NOTE again other methods can work and Im NOT arguing their use, Im ONLY stating my preference and how I was taught and polarized a Class B over the years DO AS ANYONE PLEASES is fine with me...to each their own I say

NOTES

POLARIZE BEFORE start up and try it??????

INSURE the Genny and VR have good grounds !!!!!!!!!

A genny can charge at EITHER pos or neg ground if properly polarized

If started (without correct polarization) and the genny is at opposite then battery polarity you can damage the VR

IT MATTERS IF ITS CLASS B OR A

IT MATTERS IF YOU ARE AT OPPOSITE POLARITY AND DIDNT CORRECTLY POLARIZE BEFORE STARTING

Enough for now not knowing what you have A or B and if its polarized to match battery etc etc etc.......

John T

 

[BarnyardEngineering]

Does the engine on the tractor turn opposite of normal? I am curious how the Autolite generator turns one way and the Prestolite turns the other.

 

[Ken Hoover]

Me too. The fan is definitely turning clockwise when viewed from the front and when the
generator is off the belt, it also turns clockwise.
Is this an indication the Prestolite generator is negative ground? My tractor has had the
Autolite my entire ownership and positive ground.

 

[Ken Hoover]

Wow, that's a lot of good information. Using your info, I would think the ending B in GMB4804B, means its a B class, but I assure you it has 2 wires coming out of the case and, when I could not find a replacement or parts, I opened it up and checked continuity from one brush post to one external and had continuity as I would expect, then verified the second wire had none. From your response, I interpret I should not have 2 wires, OR its a A class which adds to confusion of Part Number but its an assumption and nothing more.
I did see many posts saying to polarize before starting and I certainly did that.
regarding the proper ground. You nailed one of my deficiencies that started this tail chasing. Initially, I could not get the motor to spin when installed but no fan belt. The gen mounting bolts were poorly grounded and I had no ground to engine block. Once I cleaned all that, the motor would spin and found it spins clockwise from front view.
I have owned this tractor for about 25 years of its 72 years. I know I never changed it, but did have it rebuilt probably 20 years ago. Back when I had a guy that could that. No one in western washington seems to know what you know.
I appreciate all the part info. I exhausted all my tricks, and when it would not spin, I figured it was a winding issue until the grounding issue came up.
thanks so much