“Generator not charging” question

[KMBeers]

I know this topic has been covered in a bunch of other posts but I am new to this and I am looking for confirmation I am at least “barking up the right tree” with my troubleshooting. My generator is not charging the battery. This is something new, it always shows 10 amps at 30+ mph driving but on a ride over the weekend I discovered that it went to zero. When you turn on the ignition the ammeter shows a slight discharge, normal for my car. When you turn on the headlights or push on the brake pedal there is from 3 to 8 amp discharge with non-LED bulbs. All of these things make me believe it is not the ammeter and the issue is between the generator and the cutout. Here are the other things I have discovered:
1) there is no voltage between the generator output terminal and ground with the engine running at 1500 rpm or so.
2) I removed the cover on the cutout and the contacts don’t ever close. The voltage between the cut out battery post and ground with the engine running at 1500 rpm or so is 6.2 volts i.e.the engine is running on the battery.
3) If I push contacts closed with a wood shim while the engine is running, the voltage drops to 5.4 volts. Adjusting the 3rd brush has no impact on the generator voltage.
4) I removed the generator from the car and on the bench I applied full battery voltage to the generator, positive lead to the case, negative lead to the output terminal and the generator runs as a motor.

My read on all of this is the cutout is bad and needs to be replaced (and the generator is ok). Am I missing something or looking at things wrong? Any thoughts will be appreciated.

[katy]

There's something wrong with the generator, it's not putting out, that's why the cutout is not closing.
Did the generator work previously?
What condition are the brushes in? Possible that they're worn out.

[ndnchf]

Original Ford cutout covers are spot welded in place. If you removed the cover without cutting the spot welds, it is either a cheap aftermarket replacement or an original that someone else has been into before. Your cutout could be bad. A generator motoring test is a good check, but there are cases where it will motor, but not charge.

I rebuild generators and cutouts on the side I rebuilt a '29-'30 model A generator a couple weeks ago that had this problem. Turned out the windings were grounded. It is rRe, but does happen. If I can be of help, let me know.

[KMBeers]

Katy and ndnchf thanks for the help. The generator has worked perfectly until a few days ago. The one thing that is bothering me and no one commented on was the 5.3 volts when the cut out was forced closed manually. Any thoughts on what is causing that?
First thing I will do is pull things apart and check out the brushes. The cut out is an aftermarket one. I recently found a NOS Ford part which I will install once it is delivered. The points on the old one are a little pitted so it needs to be changed anyway

[ndnchf]

A number a different things could caus the 5.3v reading. But manually closing the cutout points if the generator is not putting out current will effectively ground the battery. It will discharge through the dead generator to ground. This will show a lower voltage.

It could be something simple like a wire in the generator rubbing on the armature. The insulation quickly wears through, causing a short. Any time the 3rd brush is moved, look closely at the wiring to be sure it is up out of the way.

[nkaminar]

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If the engine was idling while you manually closed the contacts, the voltage would be low. If that was the case then try it again at a fast idle, about 1,200 rpm.

Measure the voltage at the generator terminal at a fast idle with the cutout contacts open. It should be high, even as much as 20 volts. If this is not the case then the generator is bad and needs to be rebuilt. If you are handy with electrical stuff, you can take the generator apart and try to find the problem yourself. First take the band off and make sure the brushes are all in contact with the commutator. This is the most common cause of generator failure. The brushes can be worn to the point where they no longer reach the commutator or they can be stuck in their holders or the springs can be bottoming out. If the brushes are good, put paper under them and measure the conductivity through the field windings and from the ground brush to ground and from the power brush to the post on the generator. Check for shorts to ground. If the commutator is dirty and black, clean it up with some fine sandpaper. Last, check the armature by measuring resistance commutator segment to segment and to ground or use a growler.

If the generator puts out a high voltage at a fast idle, then the cutout is bad.

[KMBeers]

I checked for the 5.3 volts both at idle and about 1500 rpm and it was the same both speeds. Makes sense there’s an issue with the generator and not the cutout. I have a 12vdc power supply and used that to see if the cutout was working and found it snapped closed right away and opened at the removal of the voltage. Looks like it is working so I dressed the points and set them at 0.017”, the gap was almost at 0.025”. At this point as a few have suggested I am looking at the generator. It looks like one of the brushes is only hitting the armature with about 25% of the face so I will start there. Stay tuned….

[rotorwrench]

The first thing I usually do is jumper around the cut out to see if it comes to life. If it does the the cut out is at fault for one reason of another. If it still doesn't generate or the output is weak then it's time to check all the internals of that generator and also check all the main wiring terminal connections and especially the battery terminals. Things always work perfectly till they don't.

[KMBeers]

Here’s an update…. I disassembled the generator and found two issues. First the bearing on the back end came out in 3 pieces so the armature was bouncing around. Second, the wire from the fixed brush to the windings had compromised insulation and was grounding against the case. Looks like I will have a rebuild to do solve my issue. Thanks again to all for the help.

[Bob C]

I think you'll find the original rear bearing is three pieces. The new one may be one piece sealed.

[ndnchf]

It may be wired wrong. The wire from the fixed brush goes to the terminal post. The wire from the winding (field coil) goes to the adjustable brush. The other field coil wire is grounded to the case.

[KMBeers]

I have installed the rebuilt generator and everything appears to be working as it should. I rarely drive my car after dark and have the standard non-LED bulbs in my lights. When running at 1500rpm the ammeter shows about 8 amps and there is 9.2 volts at the post on the generator with no lights on. At idle the voltage reads 8.2 volts. From what I have read in other post here that seems about right. Am I missing anything?

[nkaminar]

For a 6 volt system the charging voltage should be about 7 volts. This is after the car has been driven for at least 15 minutes and the battery has regained full charge after starting the car. You should adjust the third brush.

When your car was new, the mechanics in the shop were told to check the hydrometer reading of the battery when the car came in for service. They would adjust the third brush according to the reading obtained. The third brush was changed depending on how the owner drove the car and whether it was winter or summer. But this was all based on the hydrometer reading.

If the charging rate is too high the battery will boil dry. Check the acid level on a regular basis.

[rotorwrench]

On a 3-brush, the battery voltage sets the overall voltage range so I don't worry as much about voltage as I do about output amperage. 8-amps is a bit high for mostly daytime driving. You will overcharge the battery if the amperage is set too high. It's best to read output with a calibrated ammeter in series with the output line so that it will only read output. The dash meter reads the ignition load while its running so if the dash gauge reads 8-amps then the ignition coil load has to be added to that reading to give total output.

[KMBeers]

Rotorwrench, the series connection you are referring to is I should put an ammeter in the wire between the cut out and the terminal box or can I measure the current between the two terminals in the terminal box? I just want to make sure I understand and cut the proper reading.

[Big hammer]

Originally Posted by KMBeers

I have installed the rebuilt generator and everything appears to be working as it should. I rarely drive my car after dark and have the standard non-LED bulbs in my lights. When running at 1500rpm the ammeter shows about 8 amps and there is 9.2 volts at the post on the generator with no lights on. At idle the voltage reads 8.2 volts. From what I have read in other post here that seems about right. Am I missing anything?

8.2 volts at idle, 9.2 volts at 1500 rpm sound like you have an 8 volt battery. 8 amps run at 1500 rpm sounds high for a fully charged battery if the battery is good. I would suggest pulling the floor, remove the battery, have it tested, and while the battery is out clean the ground terminal at the frame. A 8 volt battery has 4 cells, original my car came with an 8 volt battery and was low on a charge that it wouldn’t crank start. I removed the battery charged it and cleaned the ground on the frame, after that it mostly stared with the starter.

[KMBeers]

This is a 6 volt battery. The battery voltage, measured across the terminals without the engine running is 6.3 to 6.4 volts after sitting overnight (without a the battery tender running) The battery has 3 cells. The battery terminals were cleaned as I stated in an earlier post. I will look to clean the frame and starter connections which seems to be a good preventive measure. On page 209 of the service bulletins it states for owners who take long daylight trips the current can be cut down to 8 amps from 10 that should be used in summer. My old generator ran at 10 amps and the car never boiled the battery dry. I am just trying to see what others have run into since I am newer to the Model A.

[ndnchf]

I run mine at 4-5 amps. I have LED head and tail lights. So that setting works fine for day and night driving. I never have to change it.