Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks


Previous Thread
Next Thread
Print Thread
Rate Thread
#482029 05/25/23 06:05 PM
Joined: Sep 2019
Posts: 73
Likes: 4
Shade Tree Mechanic
OP Offline
Shade Tree Mechanic
Joined: Sep 2019
Posts: 73
Likes: 4
What screw is on the back of the generator to adjust the third brush. I am confused by the directions and not familiar with this type of generator. Do you move the brush in to the motor to increase amperage or away from the motor? Thanks Paul

Joined: Jul 2005
Posts: 3,192
Likes: 8
ChatMaster - 3,000
Offline
ChatMaster - 3,000
Joined: Jul 2005
Posts: 3,192
Likes: 8
The screw on the back plate is to loosen the clamp on the third brush. To access the
third brush , the metal cover band has to be removed, and then the third brush is pushed around the commutator by hand, anti clockwise to increase current and voltage and clockwise to reduce current and voltage, ( looking from the back of the generator).


JACK
Joined: Sep 2019
Posts: 73
Likes: 4
Shade Tree Mechanic
OP Offline
Shade Tree Mechanic
Joined: Sep 2019
Posts: 73
Likes: 4
Hi jack39rdst,
Thank you for your help on the 3rd brush adjustment.
I have a problem that I do not understand.
When I move the third brush away from the engine block, the amperage decreases.
When I move the third brush to the engine block, the amperage increase to just about 0 on the amp gauge.
I am working with a friend to help me as I have a learning disability.
We found that the amperage to my 28 truck was almost pegged on the charge side. We removed the voltage cut out and found out from another friend that the cut out was modified to be a diode (?), so that the electrical current would only flow one way and not back feed into the generator. I have never seen this before as the cutout was modified to remove the points?
We installed a new, old stock, cut out that came with the car. We made sure that the cut out was installed correctly. We looked at my friend car and made sure that my cut out was installed the same way as his generator cutout.
Now, the this is what happened once we started my truck.
First, we found the third brush and made sure it would move forward and backwards before starting the truck.
Once starting the truck, the third brush was moved away from the block and the amperage gauge indicated a negative decrease.
Next, we moved the third brush in the direction of the engine block. It went so far and stopped. The amperage was at zero. We used an analog meter and it read about 6 volts.
We ran the truck and the cut began to show a negative discharge.
Ok, I am not anyways a genius with electricity as I consider it to be “FM”-“ friggin’ magic”.
Is the generator cut out bad? How come I cannot get the third brush to regulate?
Thanks
Paul

Joined: Jul 2005
Posts: 3,192
Likes: 8
ChatMaster - 3,000
Offline
ChatMaster - 3,000
Joined: Jul 2005
Posts: 3,192
Likes: 8
Ok , there is directions for adjusting the 3rd brush generator at www.1931chevrolet.com. It for for a 943-J. Third brush generator , but is basically just a slightly later version..

Ok , I think firstly, The diode modification will not cause any issues
The ampere meter in the truck, did it/ does it read discharge when you pull the lights on without the engine running, or does it read charge. This will check if the ampere meter is wired back to front. Lights on = Discharge = Ok.

Have you fitted a new battery recently. When I first put a new battery in my 1939 sedan, the ampere meter read zero for quite a bit of time, until the battery lost some of its full charge, and then the contacts closed up to allow the generator to recharge the battery, a full battery should mean the contact points are open and no charge needed or flowing from the generator,

With the voltage readings, check the battery at the terminals, without the engine started, and find the voltage of the battery, should be around 6.6 volts to 6.8 volts .

Start the truck and recheck what voltage you have again at the battery, and also at the generator side of the cut out, the generator should be about reading about 7.2 to 7.4 volts, which is needed to charge a 6 volt battery,
Try these things and see what you can work out from there,


JACK
Joined: Sep 2019
Posts: 73
Likes: 4
Shade Tree Mechanic
OP Offline
Shade Tree Mechanic
Joined: Sep 2019
Posts: 73
Likes: 4
I installed a new battery about a year ago. I did put the battery on my 6 volt charger and made sure it was fully charged. I checked the wiring to the ammeter and it appears to be wired correctly as it shows a discharge when the lights are turned on. The ammeter needle moves significantly to discharge.
I use an analog meter to check voltage readings. I have a Simpson meter and another meter I use because I can zero ohms
I get about 7 amps on the non Simpson meter. I will check it today with the Simpson because I can read the meter easier.
You brought up a good point that I forgot and that the ammeter will read zero if the battery is full charged. The points are open. I also understand that the engine rpm's need to be high enough to turn the generator to work. Idle on an engine will show no discharge.
I have been working on model t fords for years where the ammeter is set with the third brush to read a constant 2-3 amps to charge the battery.
Again, what bothers me is the third brush needs to be pushed to the engine to get a positive amperage. Any movement of the third brush away from the engine shows a discharge.
I will let you know later today how I make out with the Simpson meter ammeter reading.
Thanks Paul

Joined: Jul 2008
Posts: 1,896
Likes: 28
ChatMaster - 1,500
Online Content
ChatMaster - 1,500
Joined: Jul 2008
Posts: 1,896
Likes: 28
I am not sure if it will help but I would polarize the generator.

Dave

Joined: Jul 2005
Posts: 3,192
Likes: 8
ChatMaster - 3,000
Offline
ChatMaster - 3,000
Joined: Jul 2005
Posts: 3,192
Likes: 8
One other thought, as you’ve changed the battery , has the new battery been installed correctly, all Chevrolets are negative ground, and has you have a history with early fords, may have overlooked this fact. ( model A fords are positive ground, even though model T fords were negative ground!!)

Once you have checked battery polarity is correct, the generator can be polarised by a short length of wire , momentarily touching both sides of the cutout mounted on the top of the generator.


JACK
1 member likes this: Dave39MD
Joined: Sep 2019
Posts: 73
Likes: 4
Shade Tree Mechanic
OP Offline
Shade Tree Mechanic
Joined: Sep 2019
Posts: 73
Likes: 4
Yes, I knew the battery was negative ground on the Chevy.
I took the truck out for a test drive and watched the ammeter. The ammeter hovered around the 0 mark, or a slightly negative reading.
I kept the truck running and used my Simpson meter to take a reading across the battery. It read about 7 amps. The third brush was pushed all the way to the engine block.

I have never had to polarize a cut out. I will try it and see what happens and get back to later today.
Paul

Joined: Sep 2006
Posts: 1,255
Likes: 10
ChatMaster - 1,000
Offline
ChatMaster - 1,000
Joined: Sep 2006
Posts: 1,255
Likes: 10
Remember the cut out won't energize (close) until the rpms are say maybe around 700, depending on how strong the spring on the cut out is and the air gap distance. After adjusting the 3rd brush a little bit you will have to rev up the engine to see where you are at.

Joined: Jul 2005
Posts: 3,192
Likes: 8
ChatMaster - 3,000
Offline
ChatMaster - 3,000
Joined: Jul 2005
Posts: 3,192
Likes: 8
Paul, you are not polarising the cutout, , you are polarising the pole pieces inside the generator , which have the field coils wrapped around them, the field coils are electromagnets, and the pole pieces retain magnetism, and increase the effectiveness of the field coils.


JACK
Joined: Sep 2019
Posts: 73
Likes: 4
Shade Tree Mechanic
OP Offline
Shade Tree Mechanic
Joined: Sep 2019
Posts: 73
Likes: 4
Ok, we tried the polarization trick and nothing happened to improve the amperage.
We had revved up the engine to see if the generator would kick in and it did not show any significant increase in charging. Still hovering around “0”. Simpson meter read 6.1 amps at the battery. Just under 6 amps at the cut-out switch.
Revved engine and turned-on lights and the needle went to a positive charge. Rechecked the wiring diagram and it was not clear as to how to wire the ammeter.
Reversed leads and turned on the lights. The reading went into the negative.
Turned of lights and the needle went back to “0” about 6.1 amps with Simpson meter at the battery and less than 6 amps at the cut-out switch.
Facing the back of the ammeter switch, we reversed the wires. The battery wire went on the right-hand post, and the lead to the ignition switch went on the left-hand post. I have not come across this ammeter wiring of having to reverse posts, unless this is unique to Chevy.
Note, I did work on cleaning up the commutator by using a very fine sandpaper and an all to clean carbon out of commutator grooves. This was done last winter.
The third brush needs to be moved to the engine block to get any positive reading.
Could the cut out be bad?

Joined: Nov 2001
Posts: 19,757
Likes: 62
ChatMaster - 15,000
Offline
ChatMaster - 15,000
Joined: Nov 2001
Posts: 19,757
Likes: 62
The battery positive wire goes on the ammeter post the furthest from the battery. Don't know why it is that way as most think it is logical to be on the closest to the battery.


How Sweet the roar of a Chevy four!
Joined: Sep 2019
Posts: 73
Likes: 4
Shade Tree Mechanic
OP Offline
Shade Tree Mechanic
Joined: Sep 2019
Posts: 73
Likes: 4
I have worked on a lot of model t fords that are wired reversed to a chevy cut out.

Joined: Sep 2019
Posts: 73
Likes: 4
Shade Tree Mechanic
OP Offline
Shade Tree Mechanic
Joined: Sep 2019
Posts: 73
Likes: 4
What an adventure with the land of electricity. I always referred to electricity as “FM”-friggin’ magic.
I found the third brush was frozen in its ability to move forward to the fender. I got it freed up and moving easier.
I placed the power source on the left-hand lead of the ammeter. This is facing the ammeter on the engine firewall. Power to the ignition switch and power lead from generator on the right-hand lead.
Engine off. Turn on lights. Discharge is in positive reading of ammeter gauge.
Reversed the two leads. Engine off. Turned on lights and discharge reading in the negative reading of the ammeter gauge.
Ok, this is the first time I have come across this ammeter wiring where the power source for the ammeter goes on the right-hand post.
I started up the truck, and moved the third brush to get about 7.0 positive charging amps.
Who am I to challenge the laws of nature? If it works, do not fix it unless the audience can come up with an answer of why I had to reverse the “normal” wiring of an ammeter?
Thanks for the support- Paul


Link Copied to Clipboard
Support The VCCA!

Enjoy the forum? Become a VCCA member! The World's Best Chevrolet and GMC Club!


Member Photos
1964 Chevrolet Impala SS
1964 Chevrolet Impala SS
by DreamChevy, February 17
My 1933 Chevy 2 Dr. Sedan
My 1933 Chevy 2 Dr. Sedan
by 1939Chevy1, November 24
Back on the road 79 years later
2 1927 Chevrolet Trucks
2 1927 Chevrolet Trucks
by 1927TRUCKS, June 7
Who's Online Now
1 members (Tiny), 82 guests, and 19 robots.
Key: Admin, Global Mod, Mod
Newest Members
NeilA, Jayhicks, Tomvanhouten, Dads29Chevy, Tractorman
18,308 Registered Users
Today's Birthdays
SabrinaKarras, Speedy1
Forum Statistics
Forums58
Topics59,072
Posts429,077
Members18,308
Most Online1,133
Jan 22nd, 2020
 

Notice: Any comments posted herein do not necessarily reflect the official position of the VCCA.

Powered by UBB.threads™ PHP Forum Software 7.7.5