I have a 26 coupe with a generator and a 6v voltage regulator that does not charge at any RPM. Following the very explicit warning against using a jumping wire across the regulator, I removed the regulator and connected the the battery wire (yellow/black from firewall block) to the generator post. The ammeter showed a large discharge as expected until engine was started. As RPM increased, ammeter showed proper charge. I thought problem was solved - bad regulator. However, when I installed a brand new diode type cutout, there was no charge again. Assuming the regulator was OK all along, I reinstalled it and checked voltages at various engine RPM. At cruise RPM, the voltage at the battery wire connector was 12 volts and at the generator post was a few millivolts! I'm sure many of you will know the answer, but I am very puzzled. For what it is worth, the armature is clean and shiny, the brushes are not even half worn, and the third brush holder is about halfway in the adjustment slot. Any help will be appreciated, John
26 generator doesn't charge
- Thread starter 26 Coupe
- Start date
Doug Money
Senior Member
You were getting 12 volts from a 6 volt regulator?
redmodelt
Well-known member
Stop!
If you are connecting the battery to the output post you are feeding 6V to the generator and it will want to motor till engine speed is enough to overcome the 6volts being fed into it. You can or will burn it out. The cutout or diode is a one way switch that allows the current to travel out from the generator through the amp meter to the battery and blocks the battery voltage traveling into the generator. If the cutout is not working you want to ground the generator output post to the generator body or engine.
You are looking for 5-7 amps output approx (not volts) at the equivalent motor speed of 20mph. Check your generator output using the AMP scale.
When the output from the generator is more then the battery then the cutout allows the current to flow to the battery and you will see a + reading on the amp meter.
I will suggest you should get the electrical book that is sold by the venders or the Ford Model T Service Manual.
The only time the hot wire from the battery should come in contact with the output post is to polarize the generator and then only to flash it. You may have an internal ground in the field coils or armature or even the brush plate. Shiny doesn't mean much, you may need to get it checked by someone that knows 3 brush generators and knows how to set the brush plate at neutral then adjust the 3ed brush for the proper output depending on how you drive the car. I drive with my lights on along with turn signals and extra brake lights so I have mine set a little higher then someone that takes longer trips in the day light with the headlight off.
If you are connecting the battery to the output post you are feeding 6V to the generator and it will want to motor till engine speed is enough to overcome the 6volts being fed into it. You can or will burn it out. The cutout or diode is a one way switch that allows the current to travel out from the generator through the amp meter to the battery and blocks the battery voltage traveling into the generator. If the cutout is not working you want to ground the generator output post to the generator body or engine.
You are looking for 5-7 amps output approx (not volts) at the equivalent motor speed of 20mph. Check your generator output using the AMP scale.
When the output from the generator is more then the battery then the cutout allows the current to flow to the battery and you will see a + reading on the amp meter.
I will suggest you should get the electrical book that is sold by the venders or the Ford Model T Service Manual.
The only time the hot wire from the battery should come in contact with the output post is to polarize the generator and then only to flash it. You may have an internal ground in the field coils or armature or even the brush plate. Shiny doesn't mean much, you may need to get it checked by someone that knows 3 brush generators and knows how to set the brush plate at neutral then adjust the 3ed brush for the proper output depending on how you drive the car. I drive with my lights on along with turn signals and extra brake lights so I have mine set a little higher then someone that takes longer trips in the day light with the headlight off.
Last edited:
Steve Jelf
Well-known member
I agree with getting the book. When all else fails, read the directions.
http://dauntlessgeezer.com/DG80.html
http://dauntlessgeezer.com/DG80.html
Thanks to all who responded. I appreciate your comments and concerns.
In attempting to keep my original posting short, I may have overdone it. The first thing I did was check the books, including the Ford Model T Service Manual, two other aftermarket books, and several well regarded websites. Most started at the same place. With the engine running, place the ends of a pair of pliers across the terminals of the cutout. If that restores the charging, the cutout is bad. If still no charge, test the generator out of the car. As the manufacturer specifically warns against shorting across the terminals of a voltage regulator, I removed it and connected the battery wire to the generator post. It seems to me that is the equivalent of a jumped cutout. This was a troubleshooting attempt. The total time it was connected was maybe one minute. The fact that the circuit reacted as expected (discharge until engine was started and charging up to 8-10 amps with increasing RPM) told me that wires and connections external to the generator and the ammeter were OK. Incidentally, as I understand it, one of the benefits of a voltage regulator is that, if it fails, it shorts to ground and thus saves the generator from ruining itself.
I was surprised that installing the new cutout did not cure the problem. I checked the voltage only to try to learn what was going on. It only further confused me and thus I thought of this forum to see if anyone had seen these symptoms before. Apparently not.
My next step is to check the generator on the bench. I suspect it will motor over nicely when I apply 6 volts to it, but that remains to be seen.
I am familiar with adjusting the third brush. I am at a loss as to how to do that with a non-charging generator. John
In attempting to keep my original posting short, I may have overdone it. The first thing I did was check the books, including the Ford Model T Service Manual, two other aftermarket books, and several well regarded websites. Most started at the same place. With the engine running, place the ends of a pair of pliers across the terminals of the cutout. If that restores the charging, the cutout is bad. If still no charge, test the generator out of the car. As the manufacturer specifically warns against shorting across the terminals of a voltage regulator, I removed it and connected the battery wire to the generator post. It seems to me that is the equivalent of a jumped cutout. This was a troubleshooting attempt. The total time it was connected was maybe one minute. The fact that the circuit reacted as expected (discharge until engine was started and charging up to 8-10 amps with increasing RPM) told me that wires and connections external to the generator and the ammeter were OK. Incidentally, as I understand it, one of the benefits of a voltage regulator is that, if it fails, it shorts to ground and thus saves the generator from ruining itself.
I was surprised that installing the new cutout did not cure the problem. I checked the voltage only to try to learn what was going on. It only further confused me and thus I thought of this forum to see if anyone had seen these symptoms before. Apparently not.
My next step is to check the generator on the bench. I suspect it will motor over nicely when I apply 6 volts to it, but that remains to be seen.
I am familiar with adjusting the third brush. I am at a loss as to how to do that with a non-charging generator. John
Farmallcub49
Senior Member
Is the null point set? Are the brush holder insulators shot? A bare field coil wire lead intermittently grounding? Generators are not too difficult, but there are some things that need to be checked out so all is well. If you want to do this yourself, get the book, trust me it will help, if not there are many people who can check them and rebuild them if needed. Where are you located, maybe someone is local and they can come over and help.
J Franklin
Well-known member
In your post you said the generator was charging 8-10 amps. if so your generator is not the problem. A diode cutout made for an A will be reversed on a T, I suspect.
Problem solved! If there were a prize for the correct suggestion, it would go to Farmallcub49. His advice that it might be an intermittent grounding of the field was right on.
When taking the voltage regulator off to try a friend's known good cutout, I noticed the generator post was a little loose. I tightened the lower nut, put the VR back on and the generator worked as advertised. After taking the dust band off, I noticed a 12 ga wire connected to the post was very close to the armature. Apparently, the loose post allowed the wire to rub on the armature until it shorted out. When I put the jump wire on I must have put a sideload on (or took it off). This allowed the wire to move enough to unground itself. When I reinstalled the cutout or VR, it went back to being grounded. I pulled the dust band off an old crusty spare generator and , sure enough, that big wire was routed well away from the armature. I'm sure many of you experienced Model T guys would have spotted it right away. Next time, so will I.
I have reinstalled the VR, rerouted the wire and all is well. I'm going to declare success and go home. Thanks to all - especially Farmallcub49. John
When taking the voltage regulator off to try a friend's known good cutout, I noticed the generator post was a little loose. I tightened the lower nut, put the VR back on and the generator worked as advertised. After taking the dust band off, I noticed a 12 ga wire connected to the post was very close to the armature. Apparently, the loose post allowed the wire to rub on the armature until it shorted out. When I put the jump wire on I must have put a sideload on (or took it off). This allowed the wire to move enough to unground itself. When I reinstalled the cutout or VR, it went back to being grounded. I pulled the dust band off an old crusty spare generator and , sure enough, that big wire was routed well away from the armature. I'm sure many of you experienced Model T guys would have spotted it right away. Next time, so will I.
I have reinstalled the VR, rerouted the wire and all is well. I'm going to declare success and go home. Thanks to all - especially Farmallcub49. John