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TOMT

AL EDEN S/G-VR INFO

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TOMT
I JUST PUT ANOTHER STARTER/GEN ON MY 3210V(ORIG WOULD NOT GENERATE). I FOLLOWED YOUR EXCELLENT WRITEUP TO TEST IT OUT.FOUND THE FOLLOWING; 1. RESISTANCE ACROSS TERM. A & F WAS 8.5. 2. VOLTAGE OUTPUT AT TERM. A & F VARIED ALL OVER THE PLACE. 3. AMMETER WAS INDICATING A POSITIVE READING( READING WAS NOT STEADY)EVEN WITH LESS THAN 12 VOLTS ACROSS TERM. A & F. 4. I USED DLC,S SUGGESTION ABOUT GROUNDING OUT TERM. F & THE GROUND WIRE DID SPARK. DIDNOT NOTICE MUCH CHANGE IN RPM. 5. WHEN DOING STEP 4 ABOVE THE AMMETER WOULD GO CRAZY & PEG OUT ON THE POSITIVE SIDE. I BELIEVE YOUR ARTICLE INDICATES THE AMMETER SHOULD INDICATE NO CHARGING. I'VE TRIED SEVERAL VOLTAGE REGULATORS(THINK THE ORIG CAUSED MY GENERATER FIELD TO FAIL) WITH THE SAME RESULTS. CAN THESE VOLTAGE REG GO OUT OF CALIBRATION? ANY WAY TO BENCH TEST? CAN THEY BE REPAIRED? HOW MUCH IS REPLACEMENT? ANY SUGGESTIONS WOULD BE APPRECIATED, THKS, TOMT

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Al
Hi, regarding: #2. 8.5 ohms is about normal when the F terminal is grounded and the A term has 12v on it the current through the field coil would be I=E/R or about 1.4 amps this is about normal field current for these units. It appears your generate field coil is good. #3 Ammeter erratic, not uncommon. The regulator probably has pitted contacts. As the requlator ages, the contacts get pitted and often the regulator behaves in an erratic manner. Add to this the fact that vibration is shaking the regulator and this affects the calibration. When you measure the voltage, if you are using a digital voltmeter, it samples and calculates the voltage and re-samples, kind of like a moving picture, If the regulator is grounded at the F terminal, the generator will be at full output. The voltage sampled will be high like 14+ volts. If the next time it samples the F contact is open, the resistor in the regulator will be between the F termninal and ground significantly limiting the output of the generator, while not opening the field circuit completely and causing extrmely high transient voltages from the colapsing magnetic field. If the regulator is working properly, the make and break will occur at a rate of up to 300 times per second, with the mass of the iron in the armature and the pole pieces the reluctance causes the output to stay pretty constant. If the regulator is getting bad or doesn't match the unit it is used with, then it switches slowly and eratically and at such a slow rate that you see this jumpy erratic behavior. As the contacts in the regulator get worn, the air gap changes, this changes the amount of pull the pole under the contact arm, so the voltage change at the generator output has to go much higher to open the contact, then when it opens the output drop is more significant. This longer Swing time makes the output more erratic. Then the spring tension on the arm that was set when the regulator was new becomes too high for the amount of air gap. When they get a lot of hours mechanical things kind of fall apart. Think of how many millions of make and breaks these contacts make at 300 times a second for the life of these tractors. #4 If your regulator is working the F terminal will have a ground on it when the unit is starting. Normally the difference is not significant, but it does affect the torque. #5 When the tractor is running and you ground the F terminal, The generator puts out all that it can. This is why when a regulator quits switiching and the generator is running continous full output and it is common for the generator field coil to burn out. The term for doing this is called: "Full fielding the generator". Regulators do go out of calibration, they can be recalibrated, It is done on a test bench, and can be done on a tractor if you have a 1/4 ohm 50 watt resistor and a carbon Pile load. When you re-calibrate one you have to recheck it after you put the cover back on because when you tighten the cover screws it changes the calibration. We recalibrate some, but most that have a lot of miles on can't be recalibrated and have them stay. If they are worn they will be erratic no matter how many times you set them. We stock parts for the strter generator units and rebuild quite a few of them. We also stock the regualtors for these and also parts and regulators for farm, automitive and industrial equipment. I am at the house and I don't know for sure without checking I think the regulators are in the 50.00 range depending on the which number. We rebuild starters, generators and alternators of all kinds, from very small ones to the largest diesel units. Hope I have addressed all of your questions. I am very busy now, but if things slow down a bit, I wil try to get the practical, "hands on" electrical troubleshooting articles written. I have some started and probably won't do a lot more in the theory areas. Good luck, Al

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