My '36 is equipped with the P1 style single cutout relay and 3 brush generator. From the time I started driving it I was happy to see max charging at about 20A by the dash gauge. I've blown several bulbs lately which has led me to start learning about this system and checking the "current" condition of mine. I was surprised to see system voltage approaching 9.9V with engine RPM near 2500 or so which has led me to try and unlearn 25 years of automotive experience so I can understand and adjust this very primitive system. I think I've got it but I'd like to run this by the guys with a little more hands on experience.
1) As a current regulated system, voltage will be forced very high if the battery and / or connecting cables exhibit high resistance
2) Field connections are internal to the alternator and not easily altered.
3) The cutout relay's primary purpose is to prevent battery discharge through the field when the engine is not running.
4) Current output is ultimately a function of the position of the "third brush" in relation to the main brushes.
If these basic rules are correct, then I have some questions:
What maximum resistance and / or voltage drop is acceptable across the battery cables? I'm measuring .2 ohms with a digital meter and maybe .3V between cutout relay and battery with engine idling.
A fully charged battery will naturally present a higher resistance than a partially charged battery. Why would the generator even be designed with constant current? Isn't high system voltage with a good battery just a natural result of this system working well?
The lights didn't seem like small solar flares when I first started driving the car. Is there a mechanical issue which may have brought on overcharging? Brushes wearing? Carbon buildup inside the generator?
Does anyone have a link or instructions on actually adjusting the third brush position? My service manual seems to believe I've done this procedure enough times to know where and how to make this adjustment. Since I'm planning a drive of several hours during daylight on Friday, is it a bad idea to set current output using a maximum desired voltage and an expected maximum engine rpm? Is the generator mounted in such a way as to prevent adjustment on the vehicle?
I've seen Tod Fitch's page on installing a small regulator and if it turns out that the generator / cutout relay on this car are original I might do the same. In the meantime I only have 6 spare bulbs to bring on this trip so I need to come up with a short term fix.
Finally, I've seen some diagrams from tractor charging systems which appear to shunt current to ground using different resistances connected to a light switch. How much current typically flows through the field coil? If the field circuit is fairly low current it can be shunted rather than interrupted and a fairly simple regulator could be made from a 6V relay and a few resistors.
I can work out most of this given enough time but I typically only have about 2 - 3 hrs available on workdays and I'm hoping to have this resolved by Thursday night. Any help is truly appreciated.
Shannen
Wow! Lots to cover here!
Quote from: 1project2many on July 18, 2012, 12:57:24 AM
My '36 is equipped with the P1 style single cutout relay and 3 brush generator. From the time I started driving it I was happy to see max charging at about 20A by the dash gauge. I've blown several bulbs lately which has led me to start learning about this system and checking the "current" condition of mine. I was surprised to see system voltage approaching 9.9V with engine RPM near 2500 or so which has led me to try and unlearn 25 years of automotive experience so I can understand and adjust this very primitive system. I think I've got it but I'd like to run this by the guys with a little more hands on experience.
1) As a current regulated system, voltage will be forced very high if the battery and / or connecting cables exhibit high resistance
True. The battery is what keeps the voltage from going too high and a bad connection to the battery can result in lamps burning out and other damage to the electrical system.
Quote from: 1project2many on July 18, 2012, 12:57:24 AM2) Field connections are internal to the alternator and not easily altered.
For a P1, yes. I think for a P2 they brought out the field ground wire and had a voltage regulation stage in a primitive two coil regulator (one coil for the cut out, one coil for voltage regulation and current regulation via the third brush). At least that is what they had on the PE ('34 DeLuxe) while the PF ('34 Standard) had just third brush regulation.
Quote from: 1project2many on July 18, 2012, 12:57:24 AM3) The cutout relay's primary purpose is to prevent battery discharge through the field when the engine is not running.
Cut out's only purpose is to act as a mechanical diode and disconnect the generator when it is not putting out power. Without that the generator will try to act like a motor trying to turn the engine over via the fan belt.
Quote from: 1project2many on July 18, 2012, 12:57:24 AM4) Current output is ultimately a function of the position of the "third brush" in relation to the main brushes.
Yes. The third brush and the RPM of the engine.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMIf these basic rules are correct, then I have some questions:
What maximum resistance and / or voltage drop is acceptable across the battery cables? I'm measuring .2 ohms with a digital meter and maybe .3V between cutout relay and battery with engine idling.
.3 volts drop across those wires sounds high. If the wires are in good condition, check also the connections on the back of the ammeter.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMA fully charged battery will naturally present a higher resistance than a partially charged battery.
Yes.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMWhy would the generator even be designed with constant current?
It was cheap and durable. And as long as your daily usage was constant you could average things out fairly well. System was inadequate for higher and/or more variable loads so when radios and heaters became standard they had to spend a little more money and put in better regulation.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMIsn't high system voltage with a good battery just a natural result of this system working well?
No. It is a symptom of over charging. You should check your battery electrolyte periodically and if it is low (over charging boiling out the water) decrease your charging rate. If the electrolyte is low density (under charging) increase your charging rate.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMThe lights didn't seem like small solar flares when I first started driving the car. Is there a mechanical issue which may have brought on overcharging? Brushes wearing? Carbon buildup inside the generator?
The two mechanical issues that bring on over voltage are bad connections between the generator and the battery and having the third brush set to too high a charging rate. Other things would decrease the voltage not increase it.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMDoes anyone have a link or instructions on actually adjusting the third brush position? My service manual seems to believe I've done this procedure enough times to know where and how to make this adjustment. Since I'm planning a drive of several hours during daylight on Friday, is it a bad idea to set current output using a maximum desired voltage and an expected maximum engine rpm? Is the generator mounted in such a way as to prevent adjustment on the vehicle?
I just looked at the '36-'42 factory service manual and was surprised that I don't see a procedure for setting the charging. On my '33 PD's Delco-Remy generator there is a lock screw on the back of the generator. You loosen that a trifle and remove the brush cover. Then you can rotate the third brush toward the output brush to increase the output or away from it to decease the output. I think, but don't know, that the later Auto-Lite generators simply had the third brush location locked by spring pressure and all you had to do was remove the brush cover and rotate the third brush.
For what it is worth, here is what the '33 PD says:
QuoteWhenever possible, the owner should have the generator charge rate set at a Plymouth Service Station, rather than attempt to do it himself. However the charging rate may be regulated by rotating the "third" brush holder ring. This is made accessible by removing the commutator end cover band. By loosening the clamp screw (13, Fig 13) the "third" brush rocker ring may be rotated in the direction of armature rotation to increase the rate, or against the armature rotation to decrease the charging rate.
Due to the additional electrical current required, resulting from the various electrical appliances which might be added to the modern automobile, instructions for setting of the generator charging rate are given for average driving.
The setting of the charging rate is accomplished in the following manner: Make sure the ammeter pointer returns to zero when all switches are turned off. The battery gravity should be tested, adjustment of charging rate being made only if the gravity of the batter is 1.270 or higher. Do not set the charging rate with a partly discharged battery. All connections in the electrical circuit should be tight. Make sure the generator is cool, approximately normal summer temperature. All lights should be turned on (head lights on bright). With ignition switch turned on, and the engine running at a speed equivalent to 20 miles per hour (32 km. per hour) on the road, or at maximum generator charging rate, the charging rate should be adjusted so that a reading of 8 amperes is registered on the ammeter. If a radio or other device is being used on the electrical system, the reading should be 10 amperes.
As stated above, these settings are for average driving. If the car is driven almost entirely in the daytime, the rates can be safely reduced 2 to 4 amperes. If driven at night, and if numerous starts are made, or if parked frequently at night with parking lights on, a higher rate may be required.
As the generator warms up, the charge rate will automatically drop and at normal operating temperature will read two or more amperes less than when cold at driving speeds of 20 to 22 miles per hour (32 to 35 km. per hour).
Low charge rate is indicated by poor starting and dim lights. High charging is indicated by frequent lamp burnouts and frequent replacement of water in the battery.
Correct charging rate will result in easy starting, good lights and normal battery warer replacement. Before the charging rate is altered, the generator belt shuld be adjusted as described uner "Cooling System, Adjustments," Page 37.
CAUTION: In no event should the charging rate be set higher than 10 amperes, as outlined above. The generator is not designed to operate safely at a higher rate.
Back in my youth when I used the '33 as a "daily driver" I sat down and calculated out how much current was needed for warm and cold starts, how much I drove at day and at night, etc. and attempted to come up with the proper charging rate. A fools errand. Just watch your battery water and adjust accordingly. Also if you normally putt around town with short trips and have things adjusted accordingly and then go on a road trip you'll find your charging rate too high. On my cross country trip decades ago I fitted a volt meter under the dash. When the voltage got too high I'd turn on the headlights until it dropped too low.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMI've seen Tod Fitch's page on installing a small regulator and if it turns out that the generator / cutout relay on this car are original I might do the same. In the meantime I only have 6 spare bulbs to bring on this trip so I need to come up with a short term fix.
Short term fix is to drop the charging rate to just enough to barely show charging on the gauge. Top up the battery with a charger if you need to at the end of the day. And avoid driving at night too much.
Quote from: 1project2many on July 18, 2012, 12:57:24 AMFinally, I've seen some diagrams from tractor charging systems which appear to shunt current to ground using different resistances connected to a light switch. How much current typically flows through the field coil? If the field circuit is fairly low current it can be shunted rather than interrupted and a fairly simple regulator could be made from a 6V relay and a few resistors.
I can work out most of this given enough time but I typically only have about 2 - 3 hrs available on workdays and I'm hoping to have this resolved by Thursday night. Any help is truly appreciated.
Shannen
Some cars had a circuit built into the headlight switch that cut out a resistor on the field circuit when you turned on the lights. Helped to compensate for the large load the lights present. But all that is predicated on getting a wire out from the field circuit inside the generator. And unless you are going to start drilling holes that is not feasible. At least is isn't on my old Delco-Remy setup.
Thanks for the reply.
I'm going to go over the connections tonight and clean everything. It's been my experience over the years that a DVOM uses such low voltage to check resistance that it won't always catch problems which occur when current flow is higher so I'll check drop at full charge and watch for a change.
I don't have a reliable ammeter capable of measuring 20A at the house so I'll probably borrow a tool from the shop. Both of my DVOM's and my old VOM measure up to 10A internally. For my own curiousity, when all connections are good and if no other problems are present I'm going to correlate voltage and current when making the adjustment which will give me a baseline for this car in this configuration and I'll carry a DVOM in the toolkit.
I have two manuals, 36-4? and 34-36. Neither details the actual steps for moving the brushes. Either it's painfully obvious when looking at the generator (and I missed it) or the instructions are in another book. No worries. I'll figure it out.
I really hope to use this car quite a bit and I can see the charging system becoming a constant maintenance / adjustment project without voltage regulation. I have no problems drilling holes in a generator case but I'll locate a spare to do it. I'm still trying to figure out what's going on with this car in terms of configuration. Some clues say P1 and others say P2. It's realistic to think the garage where that car was serviced years ago swapped out a generator w/ regulator for another used part because grandpa didn't want to spend money repairing the original. If that turns out to be true then the solution is as easy as installing a correct generator with regulator.
For reference, this page does a good job of detailing brush adjustment.
http://restorecarsclassifieds.com/wiki/show_pdf.pdf?n=7405
Thanks again.
Found something in the non-Chrysler issued 1933-36 Plymouth Mechanic's Repair Manual (I've seen them with different covers including NAPA). I've attached the scans.
You can easily settle the P1 versus P2 issue by looking at the serial number found on the passenger side front door hinge post.
Scans are slightly too large to attach both to one post, so here is the first.
Second scan
Thanks Tod, this helped more than just 1-2many, I appreciated the help also.
SD Glenn
1project2many, you might be over thinking this. But first a couple of thoughts...
The generator is spec'd for maximum charge rate at 2500 RPM. Not stated, but implied by the fact this must be a bench test, is that this should be generator RPM and not engine RPM. Without going to my car and measuring I can't be sure but I think the crank pulley is at least twice the diameter of the generator pulley, so we are talking something like 1200 RPM on the engine. Assuming you have 16" tires and a 4.11 rear end that would be about 25 MPH. So when you adjust the generator keep that in mind.
Next, you already have an ammeter with range sufficient for adjusting the generator. It came from the factory and is located in front of your steering wheel. :) Yes, it might be nice to do it the old time professional way by removing the wire from the generator and attaching a calibrated test high current capacity ammeter but it is not absolutely required.
So all you need now is a flat bladed screw driver to pry off the spring clip that holds the generator brush cover band in place. And to be complete, a battery hydrometer.
So shade tree mechanic's way of doing this:
1. With everything off, verify that your dash ammeter reads zero.
2. Remove brush band cover from generator (on the Delco-Remy you need a flat bladed screwdriver for this, I assume the same for Auto-Lite).
3. Start the engine and using the hand throttle adjust the RPM for maximum charging shown on dash gauge.
4. Move the third brush until the rate is what you want.
5. Shut off the engine, replace brush band cover.
6. Dig down to battery under driver seat and check the level of the electrolyte in the battery. Given that you were over charging you'll like need to add distilled water. In the future use the hydrometer to check state of charge to see if your overall rate is too low.
Probably 10 minutes total. For the moment forget about that 0.3v drop between the generator and battery. We are dealing with a current adjustment here and the battery will get charged. If you are in the range needed at the battery (6.4v) then your lights will be seeing about 6.7v which is well within their 6 to 8 volt rating.
At to the rate you want to set, I'd start out at about 8 to 10 amps at maximum charging RPM. This will drop to a few amps at 50 MPH. Not enough for night driving for long distances but enough that you'll probably keep a reasonable battery charge for typical hobbyist driving.
I probably am putting in extra effort to ensure I've crossed T's and dotted I's. The family is riding along and the last thing I want is a breakdown with a bored and angry toddler, a crying 1 yr old, and an unhappy wife. I dont want my next post to be a "how to" for converting a '36 into living quarters. :)
QuoteAt to the rate you want to set, I'd start out at about 8 to 10 amps at maximum charging RPM. This will drop to a few amps at 50 MPH. Not enough for night driving for long distances but enough that you'll probably keep a reasonable battery charge for typical hobbyist driving.
If the dash ammeter is right then I believe the rate of charge and charge voltage do not correlate properly. I'm seeing almost 10V at 20A and over 8V at 10A. Battery is about a year old but has only been in service for about a month. Battery measured about 6.8V after a small discharge period and electrolyte level was correct so I did not initially suspect the battery. I will be bringing home appropriate tools to check condition of 50+ year old cables, 70+ yr old ammeter, and 1 yr old battery. When I am satisfied those components are ok then I'll adjust the charging level.
Shannen
You mentioned that your battery is a year old, but has only been in service for about a month. Somewhere on the internet should be a way to tell when your battery was actually manufactured by looking at a code (probably numbers & letters) that is on your battery. I don't think that the battery is affecting your high voltage, but it would be good to know exactly how old the battery is (when it was actually manufactured vs. when you bought it).
Pat O'Connor
Quote from: 1project2many on July 18, 2012, 02:09:28 PMI dont want my next post to be a "how to" for converting a '36 into living quarters. :)
On the '33 two door sedan you can pull the rod that the front passenger seat pivots on and turn the seat around. Then put enough of your luggage, etc. on the floor between the reversed front seat and the rear seat cushion to level out the area. Makes a reasonably comfortable sleeping area. I did that on my cross country trip decades ago (too frugal to spend every night in a motel/hotel room).
Thanks for the chuckle. Good to know that I'll always have a bed as long as I have the car.
I'm done for the night. I cannot reduce charging current below about 10A at 1500 rpm via the third brush. At that point system voltage is 8.9V. I turned on the headlights to see how much current they would draw and one of the bulbs blew. This is not acceptable. Electrolyte level is fine, hydrometer check shows fully charged, top of the scale readings. Multiple voltage drop tests show a maximum combined drop across both battery cables is about 1/2 volt. After doing a bit more reading I wondered if maybe there was a thermostatic regulator inside the generator which wasn't switching so I disassembled the generator but no luck. While I was in there I disconnected the ground side of the field and connected it to a wire running outside the case. If I had a 6V relay I would have made a crude voltage regulator but I believe I'll just connect it to a ceramic resistor to lower field current.
I just don't understand all I know about this but my day starts in about 5 hours so I can't chase it anymore tonight.
Built a solid state regulator today at work based on a 12V version I found on the web. So far system voltage doesn't exceed 8V and generally stays around 7.4-7.5V. We're going for it tomorrow.
Quote from: 1project2many on July 20, 2012, 01:06:44 AM
Built a solid state regulator today at work based on a 12V version I found on the web. So far system voltage doesn't exceed 8V and generally stays around 7.4-7.5V. We're going for it tomorrow.
I'm very impressed. It would take me much longer than that just to decide to make a regulator much less get and implement a design.
Thanks Tod, but it's maybe not so impressive all things considered. I wouldn't abandon the plan to take the car and I just wasn't able to solve the initial problem. Finding a workaround was the only way and it just made sense to limit voltage by controlling generator output. But I'm no engineer so I had to rely on someone else's design. I started with a Delco alternator circuit but during the process of working out component values I stumbled on a regulator for a 12V motorcycle generator which was more appropriate. Changed a few resistances and on paper it worked. It was really nice to see it behave on the car.
As a final followup, it turns out the original problem was internal to the battery. The drive down Friday was trouble free but Saturday AM the car wouldn't crank over. Testing showed high resistance within the battery (6.2V at battery with no load, 0V during crank, hydrometer indicated correct state of charge) so I bought one at a local store. After that I was able to follow your original suggestion and adjust current output to just under 10A peak. Worked very well and I was able to put the regulator into the box of spare parts. Someday I might try to install the correct generator and hide my solid state regulator inside an old case.