And of course we assume you checked charging system circuit breakers that may have popped out.
--- In [email protected], iflysmo...@... wrote: > > Hey DTaylor: I am no expert, but here are some of the things to check/try: > It is very easy to test the generator on the plane. The test is > definitive. > > Disconnect the ground from the battery. Remove all the wires from the > generator. Connect a volt meter between the armature of the generator and > the generator case (ground). Connect a jumper wire from the field terminal > to the generator case. Start the engine. Voltage should track RPM's and > reach 13-14 volts by the time you get to about 1500 RPM (probably sooner). > If this test fails connect the volt meter from the field terminal to ground > and repeat. If you get a volt or two, the generator is bad. If you get > nothing flash the field then repeat the first test. > > Troubleshooting Alternator and Generator Issues: > > > DC Charging systems can be identified as "A" or "B" circuit. It is > necessary for the technician to determine > which system he has in order to properly troubleshoot. The "A" system > controls the output by regulating the > field circuit to ground. The "B" circuit controls the output by > regulating > the battery to field. > > All Delco Remy Generator charging systems are "A" circuit, therefore their > regulator controlled how much > ground was placed on the generator field circuit. This was originally > accomplished by a vibrating point system > in the voltage regulator. The more the points were vibrating toward the > closed position the more the output. > The further apart the points were during the vibrating function, the less > the output. > > The solid state generator controls work by controlling the generator field > to ground through a system of > electronic components rather than the vibrating points. The theory > remains > the same, the more ground on > the generator field, the more output and vice versa. > > Most general aviation alternators are "B" circuit. In order for them to > output current from the alternator, > battery must be applied to the field. The more battery to field, the > higher > the output. The regulator is then > assigned the task of controlling the amount of battery to field. There > are > some general aviation charging > systems that are of the "A" circuit type. These are normally found in > Prestolite alternator systems with two > field terminals on the alternator. If neither of the fields is grounded > to > the frame of the alternator, then > the system is "A" circuit. This simply means that the voltage regulator > is > controlling the alternator field > to ground to control output. > > The reason it is important for the technician to determine whether the > system is of the "A" or "B" style is so > that they can proceed to diagnose the system. A common method of > diagnosing > charging system problems begins > with the full field test. This test is used as a method of determining > whether the generator or alternator is > functioning. Since the regulator controls how much battery or ground is > being applied to the generator or > alternator, the full field test requires bypassing the regulator and > jumping full ground or battery to the > field circuit. This causes the generator or alternator to charge at full > output when rotated at cruise RPM. > > If you are testing a Delco Remy Generator system, remove both the armature > and field wires from the generator. > To prevent damage, cover the wire ends with tape. Next, jump the field > post > on the generator to a good airframe > ground. Connect a DC voltmeter to the generator armature terminal. > Connect > the plus side to the post and the negative > side of the meter to ground. With the field grounded the generator, if > good, will generate a voltage on the armature > terminal. The voltmeter should follow the throttle. The more engine > speed > the more output. Using a digital meter in > this application is sometimes not effective. An analog (needle movement) > meter is much more reliable. > > Should you have a Generator that is not Delco, it could possibly be of > the > "B" circuit, Field to Battery, type > application. If so, follow the instructions in the previous paragraph, > except connect the jumper from the Armature to > the Field post. Then connect the meter from the armature post to ground > and measure the output voltage. Normally, > the generators manufactured by Bendix, General Electric and Leece Neville, > > adopted the "B" circuit method. > > When testing general aviation alternators, the brands encountered will be > Ford, usually found on Cessna and Chrysler > on most older Pipers. You might also run across Delco Alternators on > various models of Piper and Beech aircraft. > Motorola units, in the form of STC approvals by Alcor or InterAv, must > also > be taken into consideration. All of these > unit are "B" circuit requiring a jumper from the Battery post to the > field > post in order to "full field". This means > you must remove the field wire, tape the terminal for protection, and > connect a jumper from the large output terminal > over to the field post. Connect your DC voltmeter from the output > terminal > to ground and the voltage should then follow > the RPM if the alternator is good. > > In the instances where you have a Prestolite charging system, you must > first determine whether the system is "A" or > "B" circuit. If the alternator has only one field post it is "B" circuit > and requires jumping battery to field. If > the unit has two field post, normally f1 and f2, disconnect both field > wires and protect. Now connect one jumper from > the Battery output post to one field post and a second jumper from the > remaining field post to ground. This will full > field the dual field models. The voltmeter is connected from the Output > post to ground as in the previous example. > > If the generator or alternator passes the full field test the next most > likely culprit is the voltage regulator. A > fairly reliable quick test is to connect your voltmeter to the wire > delivering battery to the regulator from the bus. > This should read battery voltage, either 12 or 24 volts depending on the > system. If you are getting good input voltage > to the regulator, connect your voltmeter to the field circuit exiting the > regulator. You should read some amount of > voltage. If the reading is zero the voltage regulator is probably > defective. > > Before replacing the regulator it is always a good idea to measure the > resistance of the field circuit. This can be > done at the regulator field wire or on the field post of the generator or > alternator. The normal reading from the > field post on 12 volt systems is 4 to 6 ohms. On 24 volt systems this > doubles to 8 to 12 ohms. This can vary slightly > and still be considered normal. > > > > In a message dated 7/12/2010 4:32:22 P.M. Eastern Daylight Time, > dtaylor9...@... writes: > > > > > Went to fly Saturday morning and found a sharp discharge on the Amp Meter > when electronic circuits were turned on. Ran up to 2100RPM with nothing on > but the radio and got no positive indication. Where do you start to sort out > what the source of the problem is. Cigarette lighter plug in voltmeter > shows 11.2 volts. 1966 Alon Aircoupe with a C90 16F. Has generator not > alternator system. >
