The Stovebolt Site Forums The Shop Area The Electrical Bay Voltage Regulator Cutout Relay

All,

I am having an issue with the voltage regulator on my '58 3200 with a 235. I have tried two good quality made in the USA replacement regulators from two different manufacturers and they both have the same issue.

The Cutout relay is not working properly. I cannot seem to get it to work reliably. Either I have it fail to activate and so I don't get any charging of the battery or it won't open and the battery drains through the generator after stopping the truck.

My diagnosis steps are the following.

First I disconnected the generator and grounded the field to the frame. I ran the truck and measured the voltage at the armature post on the generator. The voltage was about 12v at idle and increased linearly with the RPM of the engine up to about 65 volts. When I rebuilt the generator I bench tested it by running it as a motor and measuring the current draw. I don't recall the number, but it was within tolerance (I think 7 amps).

Next, I checked all of the wiring. I checked for shorts in the wires as well as touching wires. I checked the engine ground, field wire from generator to regulator, armature wire from generator to regulator, charge wire from regulator to ammeter and charge wire from ammeter to positive post on the starter. All wires are good. No shorts to ground and no wires shorting to each other. I connected and triple checked the connections.

Then, I checked that the regulator is properly grounded. I checked continuity between the regulator base, the generator frame, the engine and the negative battery post. All grounding checked out and I double checked all the connections.

I verified that the generator and regulator are working to regulate the voltage by measuring the voltage at the armature post on the regulator while the truck is running. At idle I have around 13 volts and it rises to 14.2 volts at high rpm.

I consistently have battery voltage at the BATT terminal of the voltage regulator. I pulled the cover off the regulator and manually engaged the cutout relay and the BATT terminal went up to the armature voltage and the battery began to charge. After restarting the truck the cutout relay again failed to engage and the truck wouldn't charge.

Neither of the regulators are adjustable. So, I bent the tab for the spring on the cutout relay to decrease spring tension. I moved it only a tiny bit and the relay began to engage. But, when I stopped the truck the cutout failed to disengage and allowed current to flow through to the generator and discharge the battery.

No matter how small of an adjustment I made I could not get the cutout relay to work reliably. It either failed to engage or failed to disengage. I followed the service manual instructions for heating up the regulator by running it for a while and then cycling the points.

At this point I am stumped. I don't think two different regulators from two different manufactures would fail in exactly the same way. It makes me think that something external is causing the failure, but I don't know what that could be.

My next step just to get the truck running is to install a large diode in the line to prevent discharging through the generator when the truck is stopped. But, I would like to find the culprit here and fix the problem.

Thank,
Chad

Most cutout relays have two adjustments, and yes, they're usually made by bending spring stops. The first adjustment is "closing voltage" and it's made by either observing the voltage produced at the Arm. terminal of the generator as the idle speed is raised, or by using a variable resistor between the FLD. terminal and ground with the F wire disconnected at the regulator. I use a 0-100 ohm 200 watt variable resistor to control field current while making this adjustment. It's much more accurate than tinkering with the idle speed. Slowly decrease the field resistance while watching the armature voltage. When the armature voltage gets approximately 1/2 volt above battery terminal voltage the cutout relay points should close and remain closed as the generator charges the battery. Start dropping the armature voltage by increasing the field resistance and as the voltage drops low enough to allow the battery to try to discharge through the generator the cutout should open. A "reverse current" of about 1-2 amps should be sufficient to cause the relay to spring open.

Here's where it gets tricky- - - -if the movable point is pulled down tightly against the cutout relay coil, sometimes the points won't open quickly enough. There's an "air gap" adjustment that must be made that allows the points to open and close properly, and I'll bet yours is too wide with the points open. You're having to weaken the spring tension too much to get the points to close, and there's not enough spring to pop the points open before the reverse current takes over and re-magnetizes the coil in the opposite direction. Reduce the air gap slightly between the movable point and the coil, and you'll be able to increase the spring tension enough to make the opening reliable with the right amount of reverse current.

IT IS ABSOLUTELY ESSENTIAL TO HAVE AN ACCURATE AMMETER IN THE CHARGING CIRCUIT IN SERIES WITH THE "BAT" WIRE WHILE MAKING THESE ADJUSTMENTS! Trying to do it with a voltmeter alone is impossible. So is trying to use the dash ammeter- - - -not accurate enough. It's also a very good idea to have analog volt and amp meters (with a sweep needle, not digital) while adjusting a voltage regulator, as the vibrating points create enough "noise" to make a digital readout go bonkers.

The above procedures are ones I learned well over 50 years ago. They worked then, and they still do now!
Jerry

Jerry,

Thanks for the great info. I will try to adjust the cutout with your procedure this weekend and report back with the results.

Thanks,
Chad

Go Jerry. Best instructions I have ever seen. Thanks to Hotrod Lincoln for this one.

has anyone ever made a solid-state drop-in replacement for the old relay type voltage regulators? they could easily be set for whatever voltage and current cut-off desired and do away with all of the gap-setting and tab-bending, etc.

i suppose there isn't much demand for such a thing, anymore.

Yes, it's been tried- - - -no, it didn't work well. The surges of current from the DC generator armature and the resultant voltage spikes give solid state electronics all sorts of problems. There's nothing wrong with old school technology, as long as people understand how to deal with it. Ballet dancers don't make good lumberjacks, either!
Jerry

I spent a little time looking into solid state regulators. There is one available from Zeftronics. It is for use in airplanes that use Delco generators. It is FAA certified and priced accordingly.

There used to be a gentleman in New Hampshire that would put a solid state board inside a regulator case to maintain original appearance, but he passed away a few years ago and nobody has picked his work up.

Since the replacements from airplanes are fancy anodized aluminum and don't look stock I figured I would just go with an alternator for a lot less money and better performance and reliability. Plus, if something goes wrong you can get a 10SI from any auto part store in the country.

I am going to do my best to get the regulator working because I want to keep it stock. But, at the end of the day I am going to drive this truck and it needs to charge.

Chad

Don't give up- - - -untold millions of 3-unit mechanical regulators worked well and lasted a long time from the 1930's to the late 1960's- - - -it's not like all of them suddenly got obsolete and non-functional! Find an original-equipment Delco regulator, adjust it right one time, and forget about it! Aftermarket new regulators are mostly foreign-made junk.
Jerry

Jerry,

I am definitely going to get the mechanical regulator working. I did the research I mentioned and provided it for informational purposes. The regulator I bought is made in the USA. It is substantially heavier than the cheap one in the truck when I bought it. It regulates the voltage great. I just need to get the cut out dialed in. I am waiting on a big rheostat that I ordered to get started. I can't wait to get it working. Thanks again for all the great info. I could never finish my truck without help from all the great people here.

Chad

In my opinion, there are two types of regulators for GM vehicles- - - -Delco, and "wrong". I've had very bad luck with aftermarket regulators, even the supposedly good ones like Blue Streak. There are about 20 suitable Delco regulators on ebay right now, some of them "new old stock". Any 12V negative ground regulator in the 30-40 amp range should work, even if it happens to be listed for a non-Chevy application like Buick, Cadillac, Olds, or even International Harvester or Hudson. The only precaution I can think of is if you're using a "heavy duty" double-contact regulator, disconnect the field wire at the regulator before grounding it to check the generator output.
Jerry

Chad,

Getting the settings right can be a little frustrating, but once dialed in the Delco VR's work great. It sounds as though you are on the right track towards figuring it out. Jerry gave me great advice when setting up my 1941 NOS Delco VR/Gen system, and it works as flawlessly as an alternator system.

Paul

I believe I have this same difficulty with a '57 261 school bus engine (12V) in my '54 2-ton dump truck. It has had two new regulators installed and adjusted by the only well-reputed shop in the area, to ever-worsening effect. I would like to try your adjustment technique even though I fear I may not have the skills to do it properly.

I have only the service manual for the ’54 trucks, which are 6V. I don’t know if I could follow their directions for adjusting the air gap (for opening reverse-current purposes) and for setting the spring tension for closing voltage. Do you know if the 12V regulators are essentially the same as the 6V ones?

Also, you put in all capitals about an accurate ammeter. Where in the procedure does this enter? — in the 1-2 amps of reverse current? Actually, I don’t understand why the coil holds these points closed when the battery voltage equals that from the regulated generator, much less exceeding it to give a reverse current. Should the coil not just stop pulling when these are equal, letting whatever spring force pull them apart?

I constantly hear that these matters are “not rocket science”, but to me they’re not far from it. I actually am a rocket scientist and this technology is at my limits. Thanks for any help.

Clarke

6 volt regulators have different-resistance magnetic coils to operate the points, so they're not interchangeable. The resistors that do the field current control when the points open are also different. The mechanics of making the adjustments are pretty much identical, regardless of voltage.

The cutout relay is the only thing that prevents the battery from discharging through the generator armature when it's not producing voltage higher than the battery terminal voltage. There is no diode or other reverse current prevention built into the generator. It's a simple on/off switch that connects and disconnects the generator from the battery, but it's controlled by armature voltage, not a mechanical switch handle. Early Dodge cars and trucks used a chain-driven motor/generator system that turned with the crankshaft all the time, and provided starting and charging functions with the same unit. It functioned as a starter when battery voltage was higher, and reversed current to charge the battery when the armature voltage rose higher than the battery. The system had a BIG knife switch on the dash to connect/disconnect the circuit, along with the ignition system. The drawback was size and weight- - - -the motor/generator was almost as big as the engine.

There is a small winding on the cutout relay armature that's wound in the opposite direction than the "pull-in" winding that not only stops the magnetism during reverse current operation, but it actually creates an opposite-polarity electromagnet that pushes the points apart. That, along with the spring tension, is supposed to snap the points open quickly and avoid sticking. The air gap adjustment is vitally important to that system operating correctly.

The ammeter is essential for monitoring charging current while making the adjustments, including the current and voltage regulation, not just the cutout relay. People are so accustomed to solid state devices and computers doing all their thinking for them that a simple mechanical relay voltage and current control system becomes mind-boggling. Some people only know how to turn the thermostat on the wall to control the temperature in their homes- - - -they would freeze to death if they had to cut and split firewood and run a wood stove to keep warm! DC generator/regulator systems are like wood stoves- - - -they work, but you have to be smarter than a 3rd. grader to make them do their job!
Jerry

Thanks so much Jerry. I had hoped the 6V instructions in the manual would apply to the 12V one. I now hope the regulator the local shop provided me is structurally similar to the original. If not I will try to get one of those Delco’s you advised are the only right ones and start over. I do have good analog voltmeters and ammeters and a variable resistor. Now all I need is more intelligence and some time.

If none of this works: A) What do you think the parameters would be on the diode you suggested, Chad, and where would you shop for it? B) If I have to abandon ship completely and get and install an alternator, are there instructions here on Stovebolt as to how one does this? I dislike this option, but I need to use my truck.

By the way, I agree with your assessments of today’s dependence on technology, Jerry. I avoid it as much as possible. I heat only with wood, move fluids around by convection only, gravity provides the water, and it’s clear I’m having difficulty even with this forum. Thanks again,

Clarke

Clarke,

I was looking at using a low voltage drop diode. Something like STPS60SM200CW. That one can handle 200V reverse voltage and 60A forward current with only ~.6V drop.

Chad

Chad, that diode looks like an excellent choice if you decide to add it as a fail safe. You would need to bump the voltage regulator setting up a little to compensate for the drop across the diode. A fully-charged 12V battery (specific gravity of 1.265) needs 14.5-14.7 volts at the battery + terminal to maintain a good charge, but the charging current needs to be <5A when that adjustment is made. Be sure to mount it on some kind of finned aluminum heat sink in a location where it will get plenty of airflow. Even low-drop diodes develop some heat as current flows through them, and flowing tens of amps instead of the milliamp or microamp current flows that most solid state circuits use needs some serious cooling! Good luck!
Jerry

Jerry,

Thanks, I was pretty sure it would work. I am not going to use it except as a last resort. People got these darn regulators to work for over a century so I know I can too.


Chad

I just found a printout of a Delco "A" circuit generator/regulator system. It's from a set of Delco tech bulletins I have that dates back to the early 1950's. The dashed red line in the cutout relay winding is the magnetism-reversing shunt circuit I mentioned that assists the point-opening spring during periods of momentary reverse current as the generator voltage drops during shutdown. 6V and 12V circuits are very similar, except for the 12V "heavy duty" regulators that use two sets of contacts at the voltage regulator. The cutout relay circuit is just about identical on all of them.

http://www.hunt101.com/data/500/D-R_Regulator_001.jpg

Jerry

I hesitate to add anything to what Hotrod has written, but I can write that I had the same problem that Chad is experiencing when I first got my truck. I had been persuaded to replace the original VR with a new one, and struggled with it for about a year. I did my best to make the adjustments by the book, but like many of us weekend wrenchers I do not have an ammeter that is needed to do the job right.
Particularly when the headlights had been on the contacts on the cutout relay would fuse themselves. I got used to watching the dashboard ammeter every time I shut the truck down, prepared to race to open up the VR and break the contacts.
Eventually I noticed that the old VR had two sets of contacts on the cutout relay while the new VR had only one set. Here is a picture of the new VR:
New voltage regulator
The original style can be seen in the shop manual.
Finally I took out the new VR, sat the old one back in, and used the shop manual and the advice from the Stovebolters to get the old one working right again.
I for one am convinced that if you are using a newer VR with the single set of contacts on the cutout relay you will have a greater challenge getting it to work well.
Karl

Jerry and All,

Success! I finally got the cutout relay dialed in just right.

I started the weekend by building a test setup for adjusting it. I mounted one panel mounted ammeter and two voltage meters in a piece of sheet metal. I added one 100 ohm 200 watt rheostat and a 100 watt 1 ohm current limiting resistor. I wired the rheostat with alligator clips and ran it inline between the voltage regulator field terminal and the field terminal on the generator. I ran the volt meters to the armature and battery terminals on the regulator. I ran the ammeter inline between the battery terminal on the regulator and the physical battery along with the current limiting resistor.

The current limiting resistor keeps the current below about 5 amps. That let me buy a much cheaper ammeter that is accurate to about .25 amps.

I started by using the rheostat to lower the voltage at the armature terminal below battery voltage. I slowly increased the voltage until it was .25-.5 volts above battery voltage (which was easy because of having two volt meters) and then loosened the spring on the cutout until it closed.

I then used the rheostat to lower the voltage at the armature below battery voltage. I kept lowering until it was pulling about 1 amp through the ammeter. It was not releasing the contact so I bent the arm holding the contacts to be closer to the relay coil. I kept repeating this until the contacts reliably opened at about 1 amp.

The second adjustment caused the first to change, so I repeated the entire sequence several times until I could perform both tests without needing any more adjustments.

The relay now works perfectly every time. I get 13.5 volts to the battery at about 1000rpm. I get 14 volts at 1500rpm. It cuts out at idle of 500rpm and starts up at the tiniest amount of throttle. The contacts also close if I put a load on by turning on the lights causing the battery voltage to drop.

Total spend on my test setup was about 30 bucks for the gauges, resistor and rheostat. I used wire, sheet metal and hardware that was laying around.

I can't thank everyone here enough. Especially Jerry for the great directions that couldn't be any easier to follow.

Chad

"I love it when a plan comes together!"

I learned that technique as a high school student, while attending the GM training center in Memphis with some of Dad's mechanics during a summer break. That was in 1962. I taught charging systems to high school and state trade school students for 30-something years. Now some of them are running their own shops. Just like an old retired teacher- - - -we walk off and leave our mouth running sometimes!

Now, go show the "professional" shop the right way to do it! LOL!

BTW, the current and voltage control points are also adjustable, if you choose to do so. The voltage control points can be adjusted with the 1 ohm resistor still in series with the battery and the engine running about 1500 RPM. Set the max voltage to about 14.5V with the resistor in place. The resistor simulates a fully charged battery, something we usually did with a 1/4 ohm resistor in series with the BAT wire. The current regulator (behind the ARM terminal on the regulator) needs to adjust to about 35 amps. Do this by putting all the load on the system you can- - -high beam headlights, high speed heater fan, brake lights and any other stressors you can think of. Since the two regulators are wired in series, it's an either/or situation, if the current regulator is working, the voltage regulator won't be, and vice versa. Have fun!
Jerry