voltage regulater

Problem started when I noticed the amp gauge was reading on the negative side . I took out the generator and found that the brush holder needed replacing , I had an extra generator and switched the brush holder , after putting it in the truck the gauge read better but sometimes negative , sometimes I'd tap it and it would read above the middle ,or just in the middle . I thought the battery might need a charge so I charged it in the truck without disconnecting the cables , couldn't get a change in the amp meter so I replaced the battery it is a large 6 volt , for some reason I thought I had an 8 volt but not , anyway no change in the amp meter so I checked the generator by taking a hot lead to the A terminal on the generator and it motored , the gages were redone by Larry and should be good and I'm looking at the voltage regulator , cleaned the contact points and still no change in the meter, just stays in the middle . when I was looking for a replacement regulator, I came across this note at the Brillman site

Note: Due to modern battery design, voltage regulators can’t be used to charge low or dead batteries. Doing so will destroy the voltage regulator and void the warranty.

Wondering if I damaged the regulator by not disconnecting the battery when charging , also when testing the generator the you tube clip I watched ,after getting the generator to motor they also connected a ground to the field terminal and it slowed the motoring ,mine had no change when I did that

Yes, it should slow the motoring when the field is energized by grounding it. It would seam you may have a field problem in the generator. Motoring without the field show the armature is working and there is residual magnetism in the pole shoes. Connecting the field will then decrease the speed of the armature but should increase the torque, as the magnetic field in poles is increased.
I don't know why Brillman says what the do. a generator should be able to put out rated current 100% of the time. No battery should be allowed to discharge fully but a generator system should be able to handle that. I guess they are using cheap regulators!

Is there a way to test the field coils to see which are bad ? I have 2 generators , maybe I can make 1 out of 2.

Yes, there are many ways, but 1st make sure it is wired internally correct.
Unlike starters that have 4 pole and brushes, the generator used on most vehicles has only two brushes and poles.
One brush should be connected to the generator case, either by the bush holder not insulated from the case or by a wire.
The other brush must be insulated from the case and will call this the hot brush (because generators can be either polarity, I will not use the terms + and ground)
The hot brush should be connected to the output or A(rmature) stud AND one side of the field (this is for a Delco type generator, which is what came on a IHC). I don't remember off hand where the hot connection is for the field, It could be at the brush or the output stud. It will be the lighter gauge of the two wires making the hot connection. The other end of the field goes to the field stud. You want to look for continuity between the hot connection and the field stud, and make sure there is a hot connection to the field.
If one coil has a break and the other is whole it doesn't matter as they are a set and get replace as a unit. You can next check for a short to ground on the field (when there is no wire to the regulator on the field stud) it shouldn't have a short to ground.
If this doesn't find the problem, or your not sure about how or what your readings are, I can go break open a generator and see if I can be more specific about my directions.
There are two types of automotive generator wireing. One is the one I described and the one IHC uses. the other differs by grounding one lead of the field and feeding hot to the field stud from the regulator, so the field is not connected to hot inside the generator. So call A and B circuit for the field. Both work equally well but the regulator is different and how you "full field" them for testing is different. The Delco (IHC) makes the ground at the regulator to full field (connected to hot inside and ground at the regulator) the other circuit used grounds the field internal to the generator and connects hot at the regulator to full field.
I only mention in case you come across another generator either on this truck or another to know there are two types of wiring for a generator. If that is confusing you, you can ignore the last paragraph for working on the truck.
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two simple tests for generator regulator, connect a bench set generator to a battery, it will "motor" like an electric motor if it is good,

to test in the truck, remove field wire from the regulator while truck is running, and ground it, this eliminates the regulator and gauge should show increasing charge with increasing RPM,

if no charge generator is bad, if gauge reads charge that increases with rpm, regulator is bad.

Update I checked my generator ,best I could , it motors when neg to the A termaial and pos to the frame and F terminal ,(positive ground ) also the field coils when checked and not connected were not grounded out to the gen casing .New voltage regulater and when I started the truck , after polarizing the generator , the amp gauge toook a bit to register above the middle , and after a warm up , when reved actually read up to 30 amps . the generator I chose ,(actuall heve 3 , they all motor ),but this one appears to have been redone , I think is a higher output model , do you need a higher output voltage regulater ? By the way I do have a large 6 volt battery in the system , at one point I may have or thought I had an 8 volt , but not now .

Six volt will have 3 cells and 8 volt will have four.
Generator amp size:
They were made in a range of sizes, the smallest had a brush band cover, one pole screw for each pole shoe and were about 30 amp cap
The next size up didn't have a brush band cover, and got smaller in diameter toward the brush end of the generator. these were 35-40 units.
The large and rare high amp are much bigger, they do have a brush band cover and have two screws for each pole shoe. these are 48-50 amp units.
To use the full capacity but not go over, you need the regulator set for the generators rating. Nothing will be harmed by using a smaller amp reg on a larger unit. The same is not true the other way around (high amp reg on a small generator)

Roger that on the 3 cells , thanks for all the info .
I was looking at the amp gauge and noticed that the needle was kind of rubbing on the face of the gauge , I adjusted it and its working much better , before it was slow to register and I had to tap it but now I can see the movement as the regulater cuts in