TR2/3/3A 3A Generator Light Again?

[karls59tr]

While searching for the reason the Gen light was on I discovered that the bottom hold down bracket
"ear" on the generator was broken off probably causing the generator to shift enough that the fanbelt was no longer tight.
I had a spare generator so I took it to a shop and they cleaned the carboned up armature and said the rest of the unit was good.
I took off the gauge cluster and tightened all the wire hold own screws and made sure the wiring from the ignition switch to the push button and Ign light were good. I polarized the generator.The car starts and runs fine but the Generator light stays on. I checked the wiring from Field to field from the voltage regulator to the Gen and tested good.
When I did the Moss Voltage Reg test from Youtube I got a spark when I touched the power from the Bat to the Field....apparently the generator is supposed to run when you do this ...correct?
Also with the engine running should I get 13.5 to 14 volts across the Battery Pos and Neg posts if the generator is charging? Any ideas why that darn light won't go out? Electrical is not my strongpoint.

 

[karls59tr]

Solved the problem. I couldn't see the forest for the trees. the generator hold down bolts weren't quite tight enough so when I started the car the belt was too loose. Tightened the bolts and system is charging again.:eagerness:
Still curious about the Batt volts when charging though.

 

[CJD]

The voltage reg controls the voltage for charge, and it varies with temperature, but 13.5 to 14v would be a good range. Under 13 is not enough, and over 14.4v would be overcharging. And, under 12.6v is no charge at all.

 

[mgedit]

Check out this post too. I did not know about lock tab Geo mentions.

https://www.britishcarforum.com/bcf/showthread.php?97937-Which-way-Does-the-Generator-Bracket-Go

One thing I need to look at on my 3, believe I just used split lock washers.

Cheers, Mike

 

[TRTEL]

Hi, You might want to check the spacing between the bracket 'ears' of the generator and the mounting points of the block bracket at the rear and the front bolt on extension at the front. If there is any space at all, find a suitable thickness washer to use as a shim to take up the slack. As little as .025" will cause a crack on those cast aluminum brackets, but usually its the front one that goes as that's the point where the greatest stresses and vibration are.

 

[karls59tr]

Good advise about that space.... never thought of that. And thanks to all for their input. Let's keep these LBC's on the road.

 

[TR3driver]

The voltage reg controls the voltage for charge, and it varies with temperature, but 13.5 to 14v would be a good range. Under 13 is not enough, and over 14.4v would be overcharging. And, under 12.6v is no charge at all.

Somewhat after the fact here, but I want to point out that is not correct for the control box used on TR2-4. The problem is that it doesn't regulate voltage directly, but rather regulates the sum of voltage and current.

So the book method for adjusting the regulator is to block the current entirely (by disconnecting wires or putting a piece of paper in the cutout contacts). With no current at all, the correct voltage setting is much higher. Nominal is 16.3 volts at 70F (20C), allowable range is 16.0 to 16.6.

In case you are wondering, yes, that means it overcharges a bit when running with no load except the ignition. And it undercharges when the load is heavy, like the headlights are on. That is the way it is designed.

One way to avoid that would be to fit a Lucas RB340 regulator, which does regulate voltage and current separately. GT6 and Vitesse/Sports 6 used them, don't recall offhand about Spits. But of course it looks different (the box is wider to accommodate the extra relay), so it probably makes more sense to just install a more modern alternator and be done with it.

 

[CJD]

That's semantics! Yes it controls current...and yes it controls voltage...

 

[TexasKnucklehead]

I think it's more than semantics. Current and voltage regulation are different, as is the sum of them. Power regulation is also different. Our regulators were intended to keep the battery charged, and avoid over current as well as over voltage conditions, but we call it a "voltage regulator".

Here's a good article I found: https://matchlessclueless.com/electrical/how-it-works/lucas-voltage-regulator/

But after all that, it still seems like magic to me. Lucas got a lot of functionality out of a little wire, a few switches and some metal.

 

[TR3driver]

Definitely not just semantics. A "normal" regulator for a generator (eg Lucas RB340) has two regulation relays; one for current and one for voltage. The voltage regulator helps avoid overcharging the battery, the current regulation is required to keep the generator from burning up. Yes, they both act by reducing the output, which reduces both current and voltage; the difference is in what they measure in order to decide when to turn down the output.

I don't believe Lucas invented this stuff; Edison was already describing the principles back before 1900 and Delco was building them for cars before WWII. Third brush systems were more popular, but the vibrating relays did get used.

 

[CJD]

I see a lot of confusion.

Current is the result of a voltage. If voltage is zero, then there will be no current.

If you need to reduce current, then you do so by reducing the voltage. Our regulators are, indeed, voltage regulators. It is also correct that they limit the current to the maximum the generators can provide. When it needs to limit the current, it does so by reducing the voltage. Using bi-metalic strips, our regulators are also temperature compensated. In cold weather they will set a higher voltage than in hot weather. Again, it adjusts the voltage produced, thereby controlling the current.

Now, another point. The manual tests the regulator voltage output to be 15.6 to 16.2 volts. You must remember that this is at open circuit. No battery and no ignition load. Since our voltage regulators are mechanical, they are time limited in their operation, unlike solid state regs that function in milliseconds. A mechanical voltage regulator will read higher with no load...thus the 16v spec. When you place the battery and ignition in the circuit, you absolutely should not ever see voltage that high. In a normal circuit, you should not see more than 14.4v, or you are overcharging the battery.

Now, there are reasons to set a regulator over 14.4 volts. Say your driving habits are to start and only drive a couple miles and stop. Under that situation, the battery does not have time to fully charge...so you can get by running the regulator setting above 15v. You are not running the generator long enough to overheat the battery. But, if you then took that over regulated car on a long trip, you will find the battery water level seems to go down...very fast! Likewise, if you normally drive long distances and find yourself constantly adding water to the battery, you can set a lower voltage to prevent boiling the water out.

In the end...semantics. If you prefer to look at the control box as a current controller, then you are right. If you prefer to call it a voltage regulator, still right. Voltage produces a current in a circuit, so they are forever interrelated.

 

[karls59tr]

At any rate I got the generator back from the shop again and they discovered that the "D" or large terminal on the back of the generator was loose causing the no charging problem and making the ignition light stay on. They soldered the terminal and did not charge me for the repair.
Interesting to note that on the generator I initially removed because of the broken "ear" on the aluminum generator hold down plate bracket(not the bracket that holds the generator to the block) but the one on the generator.....one of the nubs on the bracket had been filed down so the generator would not butt up against header down pipe. I now remember filing it down years ago. Guess I'll have to do the same to the new generator and rig up a heat shield as well.

 

[TR3driver]

You are still missing my point, John. Yes, I know quite well that voltage and current are related, much like torque and horsepower are related. Can't have one without the other. But you can measure them separately, and in fact they indicate quite different things because they are quite different things.

The RB106 control box does not regulate output current and voltage separately. Instead, it has a single relay that reacts to an addition of current and voltage.

One way of looking at this is that the voltage set point gets reduced by whatever current the generator is producing, even if it is only producing enough current to run the ignition. The relationship is approximately 0.13 volt reduction in set point for every amp that is flowing out of the A1 terminal (to power headlights and so on).

So if, to follow your example, you set the open circuit voltage to 14.4 volts, then run with a load of 15 amps (eg headlights and heater on), the set point is reduced to 14.4 - (15 * 0.13) = 12.45 volts. This is not only not enough to charge the battery at all, it will actually let it run down while you are driving!

But, if the voltage and current were regulated separately (for example, by a Lucas RB340 regulator), then the voltage set point is not affected by the output current.

Also worth noting, perhaps, that the current is not regulated to protect the battery at all. The current is regulated to protect the generator! Unlike alternators, DC generators will happily generate enough current to burn themselves up. (And one of the big advantages of alternators is that they are self-limiting and hence do not need current regulation.)

 

[CJD]

I am glad the repair was an easy one, Karl!

Randall, I never said to set the open voltage to 14.4. Set OPEN voltage to 16v, as the manual says. What i said is that when you bring in the loads it will reduce to about 14 to 14.4v. We are saying the same thing there.

Why do you think there is no attempt to protect the battery? Everything electric in the car is chosen to be optimized at a 6 cell lead acid battery voltage. The battery charge/discharge is a major design parameter. The voltage chosen is absolutely chosen to optimize battery charging without under or overcharging.

Now, start your car and check the voltage at the battery. It should be 12.6 to 14.4v. Rev the motor and voltage will reach about 14v and then stay the same, no matter how much you rev it. Still revving, Hit the park lights and volts will stay the same. Brake lights, ditto. Now, hit the C39 generator with all lights, radiator fan, radio, heater fan...the voltage goes down to limit the current. Summary...the controller regulates to a voltage, and it will reduce voltage only when the load exceeds the generator rating. That is why you should use the correct regulator for the rating of the generator you have.

To be descriptively correct, a generator has a rating that is the product of volts and amps, not the sum. So, our C39 with 14 volts times 19 amps gives a 266va rating...or .266kva. my RV generator has an 8 kva capacity.

 

[TR3driver]

Why do you think there is no attempt to protect the battery?

Read it again, I didn't say that. First take off your "voltage is the same as current" filter.

The voltage chosen is absolutely chosen to optimize battery charging without under or overcharging.

Well, "optimize" might be too strong a word, but the key point is that the battery needs voltage regulation, not current. While the generator primarily needs current regulation to avoid overheating the commutator and windings. Lucas tried to achieve both with a single relay, resulting in significant compromises in both areas.

Summary...the controller regulates to a voltage, and it will reduce voltage only when the load exceeds the generator rating.

Simply not true with the stock regulator. The voltage goes down as the current increases. That is exactly why the charge tapers off (ammeter goes to zero), long before the voltage rises to the "open circuit" setting.

To be descriptively correct, a generator has a rating that is the product of volts and amps, not the sum. So, our C39 with 14 volts times 19 amps gives a 266va rating...or .266kva. my RV generator has an 8 kva capacity.

Also not true, of a DC generator. (Your 8kva RV generator is actually a low frequency alternator and they are different.) If, for example, you take that very same C39PV2 and connect a 6v battery and regulator to it then try to get anywhere near 266 watts (which is the same as volt-amps, when discussing constant DC), it will promptly overheat and burn up. It can only handle 19 amps, no matter what the output voltage is. Assuming the insulation can handle the extra voltage, you could get 24 volts out of it at (almost) 19 amps as well.

Basically, because the voltage is created by spinning the armature in a magnetic field, the heat generated inside the unit is not proportional to voltage times current as it is usually. It does go up some with increased voltage, but not a lot.

BTW, the same is true of automotive alternators. You can wind the voltage way up (if the diodes will take it) and still get about the same amount of current out of it. It used to be a popular conversion, before the advent of battery powered tools, to stick a 110v regulator and outlet onto the alternator, so you could run a Skilsaw or whatever where there was no land-based power. Of course, you had to be careful to only try to run "universal" motors on the DC, but most hand tools have either universal or DC motors inside. Almost anything with brushes will run on DC as well as AC.

PS, I couldn't find a write-up, but that is what is inside this:
https://www.ebay.com/itm/ANES-E-Z-P...-Generator-12VDC-110VDC-Vintage-/221243293265

 

[CJD]

On the off chance you were right, and voltage does go down with load, I went out last night and drove the car. The turn signals use 2 amps when the bulbs flash on. So, if the voltage does go down as load goes up, then the headlights would dim slightly when the turn signal flashed on. They do not dim. I confirmed by reading the voltage, and it fluctuated with the change in load (both above and below 14.4 as the bulbs went out and relit), but smartly came right back to 14.4 volts. Last month I had the pleasure of cleaning and tuning 3 regulators form a TR2, TR3, and TR4. They all behaved this way. The voltage only goes down significantly as you approach the limit of the generator current. The only other possibility is that all 3 regulators I worked on were newer models.

None of my statements are incorrect...but you are trying to disprove them with unrelated examples. For example:

If you put a 6v battery in our cars it will not fry the generator, as the regulator will limit the output to 19amps, by reducing the voltage. Now, if you drive a long time with the generator producing 19 amps, you will eventually fry the generator from the continuous high load. You WILL fry the battery. IF you could fry the generator in that scenario, like say you have a 30 amp regulator, then the amps would go up. If the volts times amps exceeded the 266va, then you would fry the gen. In your example, let's say 30 amps times 10 volts equals 300va...that exceeds the generator capacity and will result in a meltdown.

I could do a line by line on your other exampes, but I do not need to. I am sorry, but we are just going ot have to agree to disagree on this.

 

[TR3driver]

Watch the ammeter with the turn signals on; you'll see that it swings wildly from side to side. The battery is supplying the extra power for the turn signals, not the generator. So your test is meaningless in regards to the regulator set point.

Perhaps your definition of "goes down significantly" is different than mine. My claim is that it goes down in direct proportion to output current. That certainly means it goes down more as you get close to 19 amps, but it starts going down with any current at all. As I pointed out before (and you apparently ignored), that is why you set the open circuit voltage to 16 volts, but the generator does not try to charge the battery to 16 volts. You will never measure that high with the generator powering the ignition.

For the 6v example, I was careful to specify "and regulator". You're quite right that the 6v regulator will still limit the current to 19 amps because the generator can only produce 19 amps regardless of voltage. If the volt-amp rating were constant, as you said, then it could produce twice as much current at 6 volts. Lucas did sell the C39 in a 6 volt configuration (the field coils are different, so they work on the reduced voltage). It was still sold as a 19 amp generator. If they could have sold it as a 38 amp generator, as you have implied, don't you think they would have? Doesn't work that way.


Let's try a different tack here. Within the RB106, there is only a single relay that controls the field winding. Do you agree with that?
That relay has only one armature, correct? Two windings, correct? One heavy wire (and just a few turns), wired in series with the generator output; the other fine wire wired in parallel with the generator output. With me so far? The armature responds to the magnetic pull applied to it by both of the two coils acting in tandem. If there is, say, 10 amps flowing through the series winding, then it will take less voltage across the parallel winding to move the armature, open the contacts and reduce the current to the generator field.

Or, since you seem to think my EE degree is worthless, read what someone else has written on the topic:
https://www.worldphaco.net/uploads/SAVING_THE_LUCAS_RB1061.pdf

I don't agree to disagree, but I do agree that I'm tired of flogging this particular horse.

 

[CJD]

Still apples to oranges

I don't agree to disagree, but I do agree that I'm tired of flogging this particular horse.

But we finally agree on something