Clocks that have governor fans must have them balanced. Either replace the blade or adjust the balance by bending SLIGHTLY the wings of the fan. Also filing some of the edge off on the heavy side will work, In severe cases, it may be necessary to cut some of the brass off. Some fans are adjustable mainly to vary the speed of the gear train; however this adjustability can apply to balancing also. Set the desired speed and then with small adjustments set the balance. GOVERNORS MUST BE BALANCED OR THEY WILL NOT WORK dependably all the time. Just rebushing and polishing the pivots will not fix them. I cannot stress this enough. Here is the typical senerio. You repair a grandfather clock. The governor bushings are just fine and the pivots are ok. The main wheel bushings are bad on the strike and the time and the depthing of the gear teeth there is way off causing power loss. Enough to actually stop the clock. You see this and know it because you have seen it thousands of times before so you are sure. You spend 6 hours working on the mechanism and finally get it back together and in the case for the test run. You test the clock and everything is fine. You take the clock back to the customer and all goes well; or so you think. A few weeks later you get a call from the customer and they complain "the chimes don't sound right". You say ok , its just run down and gotten out of sequence. You do a service call and when you get there everything is fine. So you check the unit out and the customer is happy , and you think all is well ... you hope all is well. Three days later you get another call from the customer. Now they are quite upset and have the same complaint. Now if you did not know about the fact that governors MUST BE BALANCED you would loose a customer and , drive yourself nuts trying to figure out why the thing keeps getting out of sequence. ( Oh, and by the way when you loose one customer what do they tell other people , and who do they tell. Well you get my point , I am sure.)
In clocks you have only a very very small amount of power available to turn the governor or the escape wheel. If the "heavy" side is down when the governor stops ; there sometimes will not be enough power to get that heavy side to overcome the pull of gravity and the strike ( or chime ) will stall once. But not every time. Now why ? Well since we are not living in a perfect world there are always going to be some inconsistancies in gear trains and gear teeth in some clocks. (Some clocks, like french clocks, and many english clocks, are so well made that this problem will hardly ever be enountered in them.) When the gears get to the point when there is, lets say, a thousandth of an inch difference in the spacing of the gear teeth on one of the gears, because you loose power exponentially as you go up the gear train, the power lost by this difference is just enough to prevent that governor from starting with that heavy side down. There could be any number of factors that combine at different times to be just enough to prevent that governor from starting. If the temperature drops slightly, the oil will add slightly more friction. If the main spring is run down there will be less power available. The humidity and temperature determine, in part, how fast the oil evaporates and thickens up. Condensation on the blades of the fan can be an issue in cool humid climates. Now you may say that this is crazy. All I can say is that if you do clock repair long enough you will find out that this is true and you will always check the balance on governors before you put the clock back together. And you will have less headaches and more happy customers. This is mainly true in grandfather clock governors as they are sometimes quite large and heavy. Spring drive clocks are susceptable because when the mainspring runs down slightly the power decreases and balance becomes more critical. On smaller governors the likelyhood of balance problems decreases somewhat; but I would still recommend checking them. If you don't on the first repair and they come back , if you are smart you will check the balance. I have repaired at least 17,000 clocks in my career and have seen problems with far more than that in training other repair technicians and I can tell you for sure if you are not aware of this problem with governor balance there will be clocks that you will not be able to figure out. If you are in business, you may be seeing a lot more of some of your customers that you want to. The downside of being aware of fan balance is that you might not get as well acquainted with some of your customers!
Governors that work by spinning weights or by friction do not have the same balance issues as air operated types because they usually start with the weights in the center. They are also not as common. In my opinion, they are not a good design for use in clocks. They are not as dependable as air operated governors because the weights sometimes stick. This causes a severe balance problem; much more obvious than that with the air operated types. Most fans ( governors ) also have a clutch that allows them to slip on the shaft . It must be tight but not too tight. If the clutch is too loose, the fan will slip and the gear train will move too fast , usually WAY too fast. If the clutch is too tight , the fan will not slip at all and not enough of the shock of the shutoff action will be absorbed and the gear train will bounce back when it stops. The shutoff cam and shutoff cam pin and any other parts of the shutoff mechanism that absorb the shock of the gear train shutting off will be damaged by the added stress that is supposed to be absorbed by the fan clutch. If the gear train recoils like this when it shuts off sometimes it will bounce back far enough to jam the lock pin in the shutoff lever. There are some clocks that are designed without the fan clutch, however. If you do enough repair you will run into these types of clocks. The governors that work with weights rather than blades are a good example of this exception. The pins, and the shutoff mechanisms are designed to take the stress.
When you do a repair check the governors. There is usually a flat spring, or a wire, through the center of the fan that rides on a small groove in the fan shaft that provides the clutch action. Some grandfather clocks, like the Herschede, use a coil spring on the shaft to supply the clutch action. I have seen many fan clutches soldered. Why? My best guess is that the repair person did not understand the system, thought it was not supposed to move, and "fixed" it by soldering. I have also seen them glued.