With credit to Cloyd VanHook:
Could running the engine with the wires reversed on the field and battery terminals of voltage regulator damage either the regulator or generator? Also, I tried to re-polarize the generator, following the directions that came with my new Zeftronics regulator. It said to disconnect the regulator wires, then connect the Bat lead to the Field lead several times, for three or four seconds each time. I saw brief sparks the first time, then nothing else. My Generator breaker tripped. I tested the generator by running the engine, but it still doesn’t work. Any ideas?
Since you have the Delco generator (externally grounded Field), you can check the generator by leaving the Batt connection on the regulator and the Gen (Armature) connection on the regulator, but disconnect the FLD connection from the regulator. With the engine running at 1,000-1,200 RPM high idle, take a voltage reading between the FLD wire and ground. I’m not sure what the number might be, but there should be some small voltage. Then momentarily ground the FLD wire. You may see some mild sparks and the generator should “load down”, putting out maximum power (for idle speed) quite rapidly. Don’t hold the wire to ground; just touch it long enough to detect an output change in the generator. Make sure all your radios and lights are off during this test, as there could be a voltage spike if the generator works. It won’t hurt the battery.
Basically, the generator should produce a very small output as soon as it starts turning (due to the residual magnetism). This appears on the Gen/Arm terminal inside the generator, and at the Gen/Arm terminal on the regulator. The regulator’s relay will internally keep that terminal separated from the Bat terminal, because the generator has not reached the cut-in voltage. If it wasn’t kept separated, the battery would try to turn the generator like a starter motor (backwards).
The Delco generator’s field circuit is internally connected to the generator’s Gen/Arm post inside the generator. With nowhere else to go at the regulator, the small voltage goes through the field instead, then out on the Fld wire to the regulator. When the generator first starts, the regulator shorts the field to ground, for maximum current flow through the field. This instantly cranks up the generator output, until the voltage gets high enough to close the regulator’s cut-in relay, at which time the generator output makes it to the main buss through the generator output breaker. As the internal voltage rises in the generator, more voltage goes to the field. The regulator then begins introducing resistance into its internal field-to-ground connection, to control the output. Otherwise the generator would “run away”.
If you connect power to the field lead at the regulator, you are putting a positive connection where there should be a negative connection (the regulator internally grounds the lead at that point). Since there is a path to ground inside a stationary generator armature, through the brushes, current flows backwards through the field and armature windings. This causes “reversed polarity”. To correct it, you have to “flash” the generator with the correct polarity. It is called “flashing”, because it only takes a fraction of a second. I cannot imagine why Zeftronics is telling you to do it multiple times for multiple seconds. That is guaranteed to trip the Gen output breaker, as you are creating a direct short circuit on the lead from the breaker. The windings in the generator are essentially a short circuit to ground when it isn’t turning. That’s why you saw no more sparks; the breaker tripped due to the short. I’m just hoping that no windings got burned out in the generator before the breaker tripped, since it undoubtedly had close to 35 amps go through it. The output side (armature winding) is made for that, but the field windings normally only handle a few amps.
If I understand the events correctly, all three wires were disconnected from the regulator during your polarization effort. You grounded the field wire, then touched the Bat wire to the Gen/Arm wire and held it there, several times. That scenario could not have hurt the regulator; only the generator. However, initially hooking up the battery and field wires backwards may have damaged the regulator, unless it has internal protective circuitry that somehow prevents it. Basically, the reversed connection meant hooking up a 35 amp, 12 volt wire to a circuit that is accustomed to five or six volts and five or six amps. The internal field relay is intended to ground that wire through a variable resistance, and (in an effort to get current through the field) may have tried to do so, since there was no alternator output. Hooking it up backwards may not have put voltage backwards through the generator. Since the field wire was connected to the regulator where the Bat wire would normally go, but the Bat wire was on the other side of the regulator, there may not have been any positive voltage applied to the field wire, unless the regulator’s internal design permitted it. If it fact it did, and you had reversed polarity, then it had to be properly flashed.
Seems to me that there are three possibilities here; possibly other less probable ones:
1. You aren’t getting battery voltage at the BAT terminal (wire on the regulator). Check it with a meter. I’m pretty sure that this isn’t the problem, but it is easy to rule it out first. The engine does not need to be running, but the Master has to be on, and the breaker in.
2. Putting all that amperage through the generator’s field windings has burned one out. Put an ohmmeter on the FLD terminal of the generator itself (with the field wire removed at the generator), and check resistance to ground on the generator case. If you get a low resistance reading (like a few ohms), the field circuit is probably OK. If you get an open circuit (or a very high resistance), the field is probably shot. Whether it is repairable depends on where it got fried inside. If it was right at the post connection, it might be fixable; otherwise the field windings will be toast.
3. The initially reversed connections on the regulator toasted the field control side of the regulator, or damaged some internal diodes. You should be able to call Zef, and ask them that question (what happens if…). While you’re at it, tell them that they sure need to revise that advice on how long to flash the field to correct polarity. It only takes an instant, and any longer can do a lot of damage. If it turns out that the generator is OK but the regulator is toast, Zef ought to make it good due to the unmarked terminals (since that’s why the got hooked up backwards, and they told you they should have been marked).