OLDMAN Posted October 1, 2018 Share Posted October 1, 2018 I need the procedure for adjusting the 3 brush Auto-Lite generator on my 1922/23 Oldsmobile model 43A. I know how to move the 3rd brush, but I need to know where to attach the leads of an ammeter. Also, do I need an ammeter of a certain capacity. Any help would be appreciated. OLDMAN Link to comment Share on other sites More sharing options...
TerryB Posted October 1, 2018 Share Posted October 1, 2018 Is there a cut out relay on top of the generator? They can be adjusted by setting the voltage to about 7 volts at the battery. A third brush unit is a kind of fixed output device that just gives a constant output regardless of load. Link to comment Share on other sites More sharing options...
OLDMAN Posted October 1, 2018 Author Share Posted October 1, 2018 TerryB, Thank you for your quick reply. There is no cut out relay on the generator, but there is one on the firewall. There is no way of adjusting it. The person that rebuilt the generator emailed me and said that I would probably have to move the 3rd brush to get the right setting for charge/discharge for the battery. When I asked how to connect the ammeter, I got no reply. OLDMAN Link to comment Share on other sites More sharing options...
OLDMAN Posted October 1, 2018 Author Share Posted October 1, 2018 TerryB, I forgot to add in my previous response to you that when the car is running and I turn on the lights, the ammeter on the dashboard reads Discharges. Link to comment Share on other sites More sharing options...
OLDMAN Posted October 1, 2018 Author Share Posted October 1, 2018 Hi again TerryB, I just read in my original manual that adjusting the 3rd brush in the direction of the armature rotation increases the charging rate and movement in the opposite direction decreases the charging rate. But I still don't know how to measure for the correct setting. Does this information help? Link to comment Share on other sites More sharing options...
Bloo Posted October 1, 2018 Share Posted October 1, 2018 (edited) Ammeters measure current flow, and always go in series with the circuit you are trying to measure current in. They never connect from a measurement point to ground like a voltmeter. For a test, To measure output of a generator I would just disconnect the main charging wire from the generator, and connect the ammeter in-between the post and the wire you disconnected. Turn your lights on high, other accessories if you have them, rev it up. If you see higher current than the maximum in the book, shut right down and readjust. There are two factors to consider when adjusting a third brush. The first is protecting the generator, because it will happily run over it's own limit and melt if you let it. The second is keeping it from boiling the battery. For what it's worth, many of them wont really do the maximum in the book for long without damage. This was and is ok, because your actual setting to keep from destroying batteries will be less than the maximum. One more thing, since an ammeter only measures flow, it does not know the difference between charge and discharge. If your test ammeter reads backwards, reverse the leads. Many old cars with third brush systems discharge with the lights on. It depends on where the maker connected the ammeter, and how high the generator is set. That ammeter on the dash isn't necessarily wrong, and I wouldn't worry about that for now. Edited October 1, 2018 by Bloo (see edit history) Link to comment Share on other sites More sharing options...
TerryB Posted October 1, 2018 Share Posted October 1, 2018 Sorry, I was thinking out loud asking about the cut out relay. It has no adjustment as you mentioned. As stated above, you may want to operate it with full lights on and accessories on then adjust for a positive ammeter reading. My only issue with that method is you can get the generator output quite high and boil out the battery. I liked setting mine by voltage, around 7.5v at the battery as not to over voltage it. Also, most times I did not drive at night so setting it to run with high beam lights and accessories was overkill for me. It is not a precise science as there is no load sensitive voltage regulator as on later autos. You kind of pick a value with the third brush setting ang go. Hope this helps! Link to comment Share on other sites More sharing options...
OLDMAN Posted October 1, 2018 Author Share Posted October 1, 2018 Thank you Bloo and TerrB for this information. I greatly appreciate the help. OLDMAN Link to comment Share on other sites More sharing options...
chistech Posted October 3, 2018 Share Posted October 3, 2018 I would set it to 7-8 amp reading during daylight driving which should give you a 0 to slightly discharge during nighttime driving. I would contact James Peterson and have him make you up an electronic regulator for your generator and you won’t have to worry about overcharging or undercharging again. Link to comment Share on other sites More sharing options...
OLDMAN Posted October 3, 2018 Author Share Posted October 3, 2018 chistech, Thank you for this information! I appreciate it. OLDMAN Link to comment Share on other sites More sharing options...
Friartuck Posted October 3, 2018 Share Posted October 3, 2018 Chistech is essentially correct here. The adjustment is a compromise. The desire is to always have the generator put enough current to overcome all the loads (usually headlights) while not discharging. The compromise is while driving during the day, you don't want to put to much current into the battery that will result in your over charging battery and "cook" it. The value of 7-8 amps cited by Christech would be combined load of lights and ignition. If you drive mainly during the day, you could reduce the current to say 5 amps. This is essentially the fallacy of a 3rd brush type generator. Link to comment Share on other sites More sharing options...
OLDMAN Posted October 3, 2018 Author Share Posted October 3, 2018 Friartuck, Thank you for your information. I really appreciate it. The question that I have is how do I set the amps to 7-8 or 5 amps. Do I use an amp meter? If so, where do I attach the leads? OLDMAN Link to comment Share on other sites More sharing options...
TerryB Posted October 3, 2018 Share Posted October 3, 2018 Is your ammeter in the car accurate? Look at it and measure the voltage at the battery when the engine is running. It seems the unknown here is the accuracy of the car’s ammeter and if it’s hooked up correctly. A lot of handheld digital multimeters have a 10 amp range. You could measure amps by putting the external ammeter in series with the output side of the cut out relay. If you accidentally exceed 10 amps to the external meter, it should have an internal fuse that will protect the meter. You could also go to an auto supply or tractor supply store and see what they sell in add on ammeters. A lot of old tractors run on 6v so they should have an ammeter that has a range that works for your car. You could use that new meter in place of the existing meter in your car. Lots of options here. I still think you need to monitor the dc volts at the battery. Have you measured that yet with the engine running? It will establish a reference point before you start any adjustments. I set my Dodge to 7v with no lights on and that worked fine. Link to comment Share on other sites More sharing options...
OLDMAN Posted October 3, 2018 Author Share Posted October 3, 2018 TerryB, Thank you for your help. I will monitor the dc volts at the battery. Link to comment Share on other sites More sharing options...
TerryB Posted October 3, 2018 Share Posted October 3, 2018 If you go the auto supply ammeter route for measuring current, that meter could be hooked up in a temporary mode at the output from the cut out relay or temporarily in place of the cars ammeter. What concerns me is if the meter in the car is connected correctly? If not correct you can be mislead to believe the battery is not charging properly. A voltage check at the battery will quickly tell you if the battery is seeing any charge. Measure the battery without the engine running to see it’s at rest value. Then start the car and measure the volts at a fast idle speed. Volts at fast idle should be higher than volts at rest. That will tell us current state of charging. From there changes if needed can be made to the third brush. Link to comment Share on other sites More sharing options...
Friartuck Posted October 3, 2018 Share Posted October 3, 2018 Use the dash gauge amp meter and set to near zero with the lights on. With the lights off should rise to about.6. Lights are a predicable load of about 3 amps each. No need to use an external gauge, just the use the one already have. if you wanted to lessen the rate, then adjust to negative 1 or so. It depends on what type of driving you plan on doing with your Olds. Link to comment Share on other sites More sharing options...
Grimy Posted October 3, 2018 Share Posted October 3, 2018 As yet, no one has mentioned the temperature compensator built into most 3rd brush generators. For example, an early 1920s car probably has a 20A generator, but the temperature compensator will reduce the (maximum) output to 15-16A (3rd brush turned all the way up) after 10 minutes or so. This is designed to permit rapid replacement of the starting electricity used, then drop back the charge level to prevent cooking the battery during a longer run. Because I do not drive my cars much at night (primarily due to headlight performance), on my 3rd brush cars I keep the HOT charge rate (no lights) to ~8 amps but use a pair of Optima batteries (200AH reserve capacity for the pair) wired in parallel to support the charging deficit with lights on for an hour or so. If I'm on an all-day tour, I'll frequently turn on the parking lights to reduce the charging rate. Link to comment Share on other sites More sharing options...
OLDMAN Posted October 3, 2018 Author Share Posted October 3, 2018 Thank you very much. Link to comment Share on other sites More sharing options...
TerryB Posted October 3, 2018 Share Posted October 3, 2018 Lots of good information from many sources here. Hopefully not too confusing. Sometimes an easy job sounds more complicated than it really is. Link to comment Share on other sites More sharing options...
John348 Posted October 3, 2018 Share Posted October 3, 2018 This is from the 1931 Chevrolet Shop Manual, might be of some help Link to comment Share on other sites More sharing options...
OLDMAN Posted October 3, 2018 Author Share Posted October 3, 2018 Great, Thank you. Link to comment Share on other sites More sharing options...
Stude Light Posted October 3, 2018 Share Posted October 3, 2018 13 hours ago, chistech said: I would set it to 7-8 amp reading during daylight driving which should give you a 0 to slightly discharge during nighttime driving. I would contact James Peterson and have him make you up an electronic regulator for your generator and you won’t have to worry about overcharging or undercharging again. This is an excellent solution that works great. Some details in the link below. http://www.fordgarage.com/pages/generator.htm On 10/1/2018 at 4:19 PM, TerryB said: Sorry, I was thinking out loud asking about the cut out relay. It has no adjustment as you mentioned. My Remy Cutout is fully adjustable but requires a regulated voltage supply to set it up properly. Adjustment is detailed in the Dykes manual. Important so it doesn't cutout inappropriately. Scott Link to comment Share on other sites More sharing options...
TerryB Posted October 3, 2018 Share Posted October 3, 2018 My Dodge was not adjustable, so yes it is not accurate to say all are not adjustable. Live and learn! Link to comment Share on other sites More sharing options...
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