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    Hello everyone. I went to a car show today and as I was parking I saw the generator light come on slightly. I reved the motor and it went out. When I was ready to leave I started the car and drove home(68 miles) when I got home I stopped the car and the generator light came on bright. I tightened the belt and it went out again. I charged the battery up for a while then took a reading on my multi tester. It read 12.80 then 12.59 I let it run for a while and it never went up or down however the light would come on and stay on, if I reved the motor the light would dim and almost go out. My question to the forum is how can I tell if the voltage regulator is going bad or the generator it self? Is there a test I can perform? Thanks in advance. Rodney

  • #2
    Usually V/reg is on or off. It sounds as if the gen is just putting out @ low voltage. Do you have a local Starter Generator shop? Sometimes they can just throw a set of brushes in em and they're good for another 10 years.
    John Byers
    1960 Convertible (Orig owner)
    sigpic

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    • #3
      They would also clean up the brush holder area which gets crapped up with carbon over time. The brushes need to be free to move against the commutator. You might try just doing some cleaning first. I am not sure if you can do this with the generator still in the car or not. It only involves taking the cover off the end. I can provide a photo as I have a spare generator.

      If you do take it to a shop, take the Regulator with you and they can test them as a pair for you.

      john
      1958 Hardtop
      #8452 TBird Registry
      http://www.tbirdregistry.com/viewdat...tryNumber=8452


      photo: http://www.squarebirds.org/users/joh...d_June2009.jpg
      history:
      http://www.squarebirds.org/users/johng/OCC.htm

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      • #4
        Hi Rodney,

        There's a chance that one of the brush wires are broken & not making a good contact. Or it could be one or both brushes are pretty well worn down. I don't know how long since the Genny was last repaired, but if it hasn't for a few years I would take it out. (1) Give it a good clean. (2) Get new brushes. (3) If the Commutator is out of round or slightly concave get it turned. (4) Get the Commutator grooves (Mica) cleaned 1/32" below the copper & then with #00 or #000 sandpaper remove any rough edges. (5) Check the bearings for slop & change them if required. (6) If the rest of it is O.K. it should last you for the next ten years or around 20,000 miles. Or if you're not a Purist now is the time to change over to an Alternator.

        Chris....From the Land of OZ.

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        • #5
          Previous posts are correct about brushes. They're cheap (~$8/set of 4) but the idea is to change them before they fail. Do not run your generator if you are not sure the brushes are ok. If they stick or are worn out, they arc and burn the copper commutator segments.





          You can test the generator by forcing it to produce full voltage (around 15-volts). Take the field wire off your regulator and connect it to BATT. The ARM voltage will increase to full volts. You can run this for up to two minutes, which should be plenty of time to troubleshoot. Either keep your lights off, during this test, or don't rev the engine real fast. Your meter should show when you approach 13.5-volts (nominal charging voltage).

          Turn the headlights on for a while to drain the battery. If the regulator isn't sending armature current to a battery that is partially drained, you will know.

          Your GEN light only comes on when the battery voltage is higher than your generator is putting out (like when you first turn the key on before starting your engine, or if you throw a belt).

          All the current to charge your battery goes through the generator brushes. They should last for about 50,000 miles.
          By contrast, an alternator has two brushes, but they only pass about one amp (to excite the field). Those brushes are much smaller and should last 100,000 miles. The whole brush holder w/brushes cost about $15. On Ford alternators, they are accessible from the back without removing the end-plate.

          Hope this helps. - Dave
          My latest project:
          CLICK HERE to see my custom hydraulic roller 390 FE build.

          "We've got to pause and ask ourselves: How much clean air do we need?"
          --Lee Iacocca

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          • #6
            simplyconnected - I have a question about the procedure you discussed. My generator is putting out about 1 volt. I pulled it and found that a brush spring was broken and the arm that pushed down on the brush was loose inside the generator. I saw no damage to anything so I replaced the spring and put it together after cleaning up the commutator. I decided to try polarizing the generator by removing the field wire at theregulator and touching it to the battery connection at the regulator. It instantly became too hot to hold.....a lot of current flowing. In your answer below you talk about the same connection being made for up to two minutes. Does this indicate I have a shorted filed winding?

            Vern

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            • #7
              Gen

              On our cars moisture gets to the bottom brush and it gets stuck in the holder. I've cleaned the holder and spring up a couple times and I'm startin to lean to an alternator. We don't drive these like we used to. (well everyday for me back in the day) You will need snow tires and chains!! .............Bill

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              • #8
                Originally posted by vernz View Post
                simplyconnected - I have a question about the procedure you discussed. My generator is putting out about 1 volt. I pulled it and found that a brush spring was broken and the arm that pushed down on the brush was loose inside the generator. I saw no damage to anything so I replaced the spring and put it together after cleaning up the commutator. I decided to try polarizing the generator by removing the field wire at theregulator and touching it to the battery connection at the regulator. It instantly became too hot to hold.....a lot of current flowing. In your answer below you talk about the same connection being made for up to two minutes. Does this indicate I have a shorted filed winding?

                Vern
                It sure looks like it, Vern. To make sure, you are talking about the FIELD wire getting too hot, not the armature wire, right?

                A shorted field winding will play **** with a regulator. Use a resistance check for your Field windings. Under full load, the FIELD should pull about an amp or two. The field and armature are both internally grounded at the end of the coil. That's why you should have a separate ground wire going to your regulator (just to be sure).

                Here's another check that most people are unaware of: The field is an inductive coil. With all wires disconnected from your generator, (bench-testing) connect a continuity light (with two AA batteries) to ground. If you 'scrape' the other continuity light lead to the Field terminal, you should see a pretty blue spark. If it's shorted, no spark, but the continuity light will shine bright.

                Just a thought; make sure you didn't ground your field wires inside the case, when you put it together. It's easy to pinch a wire, there isn't a lot of room.

                The ARMATURE current will be around 35-45-amps. Replace that wire with at least a #10-AWG.

                Sounds like your field wire may have got cooked. No biggie, it goes from your regulator to your generator and nowhere else, and it hangs in free air. That wire is skinny because only one or two amps go through it. Remember, the voltage regulator turns your field on and off. Then the field magnetism controls the armature output.

                You should be able to tie the armature and field wires together, run that wire to Battery, and watch the generator put out like gangbusters. Remember, it's un-regulated. Be careful you don't put out too much voltage by reving too high. I like to use an old headlight for the load. You can see it go from dim to bright with rpm changes.

                Field wires are connected in series. You can buy field windings. Use a crimp connector (not solder) when connecting inside.

                Hope this helps, Vern. If I'm foggy on a point, please re-ask. - Dave
                My latest project:
                CLICK HERE to see my custom hydraulic roller 390 FE build.

                "We've got to pause and ask ourselves: How much clean air do we need?"
                --Lee Iacocca

                Comment


                • #9
                  charging woe's

                  Thanks for the info, I have copied it and will study it. I dropped the generator and the VR off a the repair shop. They asked me about converting to a solid state VR have any of you used one of these? With all the talk about the "bushes" it seems that they are the only thing I would want to change to last longer. The generator is kind of difficult to remove unlike the other generator cars I have, How difficult is a alternator conversion?
                  Last edited by birdbrain; September 21st, 2009, 07:25 PM. Reason: spelling

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                  • #10
                    Originally posted by birdbrain View Post
                    ...How difficult is a alternator conversion?
                    Serious talk? There's a host of reasons why EVERY OEM dropped generators and voltage regulators, in favor of alternators. Where do I begin?

                    The numbers: The smallest of alternators (70-amp) outputs twice the power of your generator (35-amp), and they charge your battery at idle speeds. Now, you can safely run all your accessories (including electric fan) without any worry about an under-charged battery.

                    They are all self-regulating, and last far longer. Parts are available everywhere, cheaper. Boneyards throw them out daily. Shaft sizes are the same as the old days, and pulleys are normally piled high at alternator shops.

                    Years ago, I converted my '55 Y-Block to a Mustang alternator. It uses the original belt/brackets and fits with room to spare. I did fabricate a "Z" bracket in my garage, to complete the installation. I made everything I needed for the conversion.

                    For me, the conversion was from 6-volt POS ground to 12-volt NEG ground. It was the best move I ever did. Don't waste your money on a solid state regulator, it's already included in modern alternators.

                    Check out the electrical schematic on my site. It shows two plugs that go into the side of the Ford alternator. All the large wires go to the battery, and one skinny wire goes to your GEN light. It's that easy. It also works the way you would expect, with no surprises. That little GEN wire senses when your ignition is on, AND it shines if you threw a belt. It also shines when you first turn the key on, and goes out when the engine rotates. - Dave
                    My latest project:
                    CLICK HERE to see my custom hydraulic roller 390 FE build.

                    "We've got to pause and ask ourselves: How much clean air do we need?"
                    --Lee Iacocca

                    Comment


                    • #11
                      generator apart

                      The shop was to busy to look at my charging system so I went and got it. I removed the two long screws and pulled the back off the generator. The brushes were very dirty lots of what appeared to be carbon, I took emery cloth and cleaned the thing that the brushes ride on, then I cleaned the large cylinder with the cloth. The "field " that is the thing inside of the generator case was dirty also with black soot or something, I cleaned that as well. I scrapped all the black paint like stuff off that. I hope I did not hurt anything as this is the first time I have been inside of a generator. The brushes and springs were ok as they moved freely and I cleaned the contact area with the emery cloth as well. My question is did I mess up anything or miss anything? When it comes to the two studs "field" and "Arm" the plastic at the base of these studs was a bit brittle should I be concerned about that? I'm I ready to put this generator back on my car now? any thoughts ?

                      Comment


                      • #12
                        Hi Rodney,

                        It's pretty hard to tell without seeing it. You say the brushes looked O.K. I haven't done a Genny for a long, long time but the Brushes should be about 3/4" from memory.
                        Even though they might look O.K. but are down quite a lot it would be best to change them. For peace of mind get a Buddy of yours who's Machenically / Electrically inclined to have a look. When Dave gets on he'll be able to go one further.

                        Chris....From the Land of OZ.

                        Comment


                        • #13
                          Originally posted by bird 60 View Post
                          ...When Dave gets on he'll be able to go one further...
                          Thanks, Chris.

                          Originally posted by birdbrain View Post
                          I'm I ready to put this generator back on my car now? any thoughts ?
                          Rod, you probably did as well as the shop would. Just a few thoughts, if I may give a little background:
                          Generators are nearly bulletproof. There isn't much you can do to damage one. Cleaning the inside is a VERY good thing as carbon dust loves to conduct electricity to the grounded case, causing a short.

                          There are a few cautions. The copper commutator should not be sanded (at all) unless the shape is distorted (egg-shaped, tapered, oval, severly scratched, etc). Those brushes you removed conform perfectly to the commutator, and if they still have good length left, they should be put back in (**more on this in a moment).

                          Bearings need grease, but as you witnessed, too much grease will spread all over the inside of the case and all the carbon dust will stick to it. So, grease the bearings before re-assembly but don't go overboard.

                          Carbon (graphite) is a natural lubricant and it conducts with resistance. It also withstands lots of heat because we pump ~40-amps through it. Your brushes need to freely slide in their holders so proper spring tension can push each brush against the commutator. A buildup of heated dirty grease will cause the brush to hang. That's when trouble starts. Current wants to pass, but an air gap between the brush and copper segments will cause burning.

                          Two things need to happen before you button it up: Grab the brush by that braided wire, and pull straight up. Feel it slide in the holder without obstruction, all the way down. If your spring is pushing the brush way down the hole, replace the brush. When finished, leave the braided wire such that it can freely extend to take up brush wear, but it won't touch any metal parts around it.

                          **I have changed many brushes on huge DC motors. We never change them all at once. They need to wear-in to conform to the commutator with decent surface area. Your generator only has two brushes. If you get new FLAT-ended brushes, find a cylinder about the same diameter as your commutator, put fine sandpaper on the surface, and arc the new brush's contact surface to conform to the commutator. Being carbon, they sand easy. A flat-ended brush will only conduct at a line of contact passing too much current over a small surface until it wears-in.

                          INSULATORS: One of your brush holders is insulated on the back plate, and the other is GROUNDED to the back plate. So, power is produced in the armature; Positive goes out the insulated brush to the stud, and Negative goes through the grounded brush to the case. You can see how important that back plate is to your system's ground. The two studs you mentioned should be well-insulated and tight. Plastic can be brittle as long as it is not broken (and shorting the stud to ground). Fiber washers and sleeves work well if you need more insulation.

                          You can check each component with a meter during the whole rebuild process. While the generator is still on your bench, check for shorted field or shorted armature windings using the technique I described below. You can do this as well as anyone else, for a whole lot less money.

                          Hope this helps. - Dave
                          My latest project:
                          CLICK HERE to see my custom hydraulic roller 390 FE build.

                          "We've got to pause and ask ourselves: How much clean air do we need?"
                          --Lee Iacocca

                          Comment


                          • #14
                            Hi Rodney,

                            I've problems at this very moment wit my GEN also, and far from being a mechenic.
                            I've never had a generator apart. However I took the shot and removed it to look (and clean) and it's just the way Dave describes.............

                            Here are some pics.......(and please experts, are these brushes OK?)
                            Attached Files

                            Comment


                            • #15
                              Hey Guys,
                              I got rid of my generator and went with a alternator. Never had generator apart but if it were me and the trouble it is to take off and put back on, would it not be best to replace brushes
                              Richard D. Hord
                              sigpic'60 Thunderbird "Christine"
                              Registry #33436

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