Last week my generator light would come on and stay on after starting the car. A quick rev and it would go out and stay out. The next start it would do the same. Couple days later and it took a high rev to get the light out, sometimes even revving it really high several times. Then it started to come on when coming to a stop. Finally the other day it came on and stayed on after starting the car. I have little idea what Im doing when diagnosing a generator charging problem. First I checked the voltage and it was only putting out 1.4V. Pulled the gen and removed the back cover and found the two brushes worn so far that they wouldnt extend further due to the wire length. Put in some new brushes and cleaned the contacts in the regulator. Then it started putting out about 10V, but now its probabbly only around 5V and will go up to about 8V or so when reving the engine. I drove the car approx. 25 miles and the battery was spent. I have not checked the amp output. I am currently charging the battery back up to normal to start fresh and continue from there. Do I need to polarize after R&I of the gen and brush swap? If so, how? I searched here and there seems to be several opinions on how to go about this. With the cover of the regulator off, what position should the relays be in with key off, key on and running? Is there a way I can check the generator? Im just looking for any ideas I can use to diag this thing! Thanks Bryan
When you polarize the generator remember to stay out the field(F), just touching the (A)rm and (B)at terminals at the regulator with your jumper wire. Always repolarize any generator after servicing it or disconnecting the battery.
The reason your light went on intitially and then back off was because it takes a specified higher RpM before the generator starts charging. The is alot of posts regarding this subject if you search. If you decide the windings on the Generator are bad. You can buy your style rebuilt at Mac's. By buying the merc generator you get a higher amp range for the same money. Heres a very basic page on generator and regulator testing. http://www.nls.net/mp/volks/htm/gen.htm
Thanks for the link. Im gonna test my battery and then test the alt. as the like suggested. Last night I searched every post about generators, but didnt really nail anything down that is a step by step how to eliminate each component. Got some good ideas though.
Take the band off of the inspection slots and look for an excessive amount of arcing of the brushes. I have had just the problem you are having and it has been the brushes either hanging up in the brush holders from dirt, rust & gunk or warn brushes or bad brush springs. Good luck.
What kind of car is this on? I had an original generator in my '61 Falcon. Had it rebuilt once and it still gave me problems and left me with dead batteries. I installed and rewired for an alternator and would recommend it in a hearbeat. Only restorers care if there is a generator in a '60s car with a closed hood. You can then use the generator in your open hood hot rod!
I had to get mine rebuilt twice. After the first rebuild, I didn't get it polarized right, and blew it again! I owned up to my shortcomings, and took it to a shop. Look at this link too.. http://www.ranchwagon.com/tech/alt/alt.htm
if you have the original voltage reg. just replace it. 35$ at autozone. make sure you polarize the reg. With the terminals toward you and the reg facing up, it would be the middle to the right one. On my comet its middle to top the way it sits on the car. Do this every time you unhook the battery or gen. The prob you're describing is definitely the regulator though. Been there.
This is a Fairlane. 221 V8. Its the factory generator, regulator & wiring. The brushes are new and contact at the commutator seem to be ok. However it might be good to note that I did not do anything to the commutator during brush replacement. There is a lip on both ends. Possible poor contact? Only contacting at the edges? My gen is marked F and G on the small wires on the side, and on the back is the black/yellow wire running over to the regulator. How would I test it? Remove all wires, ground jumper from G to chassis, and voltmeter inline from the rear terminal and then start the car? The link refers to different labels... Maybe I should put an alternator on this thing!
Here are some good directions on testing both units. [FONT=Times New Roman, Times, serif]Both the generator and the regulator are really easy to diagnose and fix, and parts are available. To sort out which is giving problems, you are going to need some test clip leads, and a cheap VOM. Thus armed, and before you do anything else, polarize the generator. Do this by momentarily touching the battery hot lead to the armature terminal on the generator. [/FONT] [FONT=Times New Roman, Times, serif]By the way, are you sure you have the polarity right? I think these cars are positive ground. [/FONT] [FONT=Times New Roman, Times, serif]When you touch the battery to the armature, there will be a health spark. Don't worry, 6 volts will never hurt you, you can't even feel it, it just looks impressive. You only need a fraction of a second to polarize the generator, so just tap the wire to the terminal. [/FONT] [FONT=Times New Roman, Times, serif]Now, start the engine and have a helper observe the ammeter. With the engine at fast idle, momentarily ground the field terminal on the generator. The generator should produce voltage at the armature terminal, at least 7 volts or so. If it does, your generator is working. See if the ammeter shows charge under this condition. If it does, the problem is either with your regulator or with the wiring. More about this later. [/FONT] [FONT=Times New Roman, Times, serif]If the generator is NOT working in this test, turn everything off and remove the generator from the car, take it to the bench and inspect the brushes and the armature for cleanliness. [/FONT] [FONT=Times New Roman, Times, serif]Clamp the front housing end in a vise, remove the two long bolts from the rear of the case, and pull the rear end off, then remove the outer case/field assembly. [/FONT] [FONT=Times New Roman, Times, serif]If it needs new brushes, or the commutator is oily, take care of that first, it may be all you need to do. [/FONT] [FONT=Times New Roman, Times, serif]Clean the commutator with "Brake Cleaner", and spin it manually while you hold a strip of find sandpaper against the contact surface. If the mica is up level with the copper, groove it with a hacksaw blade so the brushes can make solid contact. If you need to replace the brushes, take the old ones to NAPA and let them match them up for you. While you have it apart, verify that there is no continuity from the commutator surface to the shaft. If there is continuity there, the armature will have to be rewound or replaced. (This is not usually the case.) Also verify that there IS continuity from any one segment of the commutator to all others. Again, if it fails this test, you need a new armature. This will be hard to find, but it is available. If your local generator shop doesn't know where, we'll help you find one. [/FONT] [FONT=Times New Roman, Times, serif]Also, check that there is continuity from the field brush terminal to the brush itself, and from the field terminal through the field windings in the outer case. If this fails, you need a new field, also not a common problem. [/FONT] [FONT=Times New Roman, Times, serif]Now you are ready to reassemble it. Do not over grease the rear bearing or over-oil the front bearing. A little dab'l do ya, here. [/FONT] [FONT=Times New Roman, Times, serif]Then retest it. You can just spin it by hand, CW from the front, and note any voltage generated at the armature terminal when the field terminal is grounded, using your VOM. This time we'll settle for any voltage at all, since you cannot spin it fast enough to get a real output. If you see the meter react at all to spinning the armature, put the generator back on the car and repeat the first test. If it still isn't putting out at least 7 volts at fast idle, it will have to be further investigated, and I recommend you take it to a professional. Pick someone who has been at it for years, so they know what a generator is. [/FONT] [FONT=Times New Roman, Times, serif]Now back to the wiring of the regulator. If the generator is now working, but still not charging the battery, try grounding the field wire at the regulator. This is the same wire we just grounded at the generator, and you should see the same result. If you don't, investigate the wire. [/FONT] [FONT=Times New Roman, Times, serif]If grounding the field wire made the generator put out, but it is still not getting to the battery as shown by the ammeter, probably you have a bad regulator. Possibly there is a problem with the armature wiring from the generator to the regulator, so check this. If you don't see anything wrong, and you measure continuity from the armature terminal on the generator to the "A" terminal on the regulator, I would take a chance and get a replacement regulator. Again, these are in stock at NAPA, just make sure they give you a positive ground 6 volt regulator. It may not look exactly like the original, but maybe after we know the new one is fixing your problem, you can decide whether or not to seek a NOS regulator, or change the case cover so it at least looks right. Often this is easy to do, and undetectable. It is important that the cover fit exactly the same, however, since it is part of the magnetic circuit of the regulator, and a wrong fit will affect the settings. [/FONT]
I appreciate all the help. I 'think' I tested the generator the right way. But the results might show a bad generator. Voltage goes from 6-7V down to 2.5ish when testing. I also checked all the wiring from the generator to the regulator, appears ok and resistance check is fine. I also watched the regulator with the engine running. On A & F of the regulator the contacts are always closed. On the B contact it is always open, slight movement to close a times, but no contact made. Idle, fast idle, high rev, same result. I did order a regulator, mainly because it was only $18 from NAPA. I should have it tommorow. I dont want to install it until I have a better idea of how to test everything better. I pulled up the diagram for my car and it looks like the oil light and generator light are on the circuit as well. http://www.tocmp.com/tOCMP/wiring/5765wiring diagrams/Ford/MWire5765-208.jpg The oil light and gen light come on with key on and the oil light goes off when the engine is running, and the gen light is not fully lit. Im assuming since this is working correctly then the ignition switch should be ok as well. I should probabbly check the engine ground as well.
i think you should turn the comutator. or at least scuff it up with some emory paper, and then clean out the grooves. good luck cadillac dave
No, the belt isnt slipping or squealing. With the car running, if I ground out the field on the gen the voltage output drops. to about 1.5v. If I close the contact to the cutout relay voltage jumps up instantly over 10v at idle. When I ground out the field, the cutout contact does not close.
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