Voltage regulators - - why do they die, and how?

Guys -

My son is getting ready to embark on some work on his grampa's Farmall C. I am a steam guy, and an F-series guy. Have little background in these electric start jobbies.

A few years ago, we replaced the 6 volt voltage regulator, and it worked fine. Now, after only a few dozen hours of use, it quit charging. Removing the cover and pressing the contacts together (on a nearly dead battery & a running tractor), it will make a charge, but quit when my finger is removed.

Inside of the regulator is very clean. Tractor was stored under a car-port.

Looking inside, it looks like some electromagnets and contacts. What fails on a regulator? Dirty contacts would think to be easy to clean.

Is there anything that should be checked before we junk it an buy a new one ? It appears to be a pretty simple device.

Thanx !

Pete

Several things can and do go wrong.
The two sections of this regulator (not all)are very much seperated from one another. The component you are probably pushing to make it charge is the cutout relay. It has two windings on it, a pull in winding of thin wire, and a hold in winding of fat wire.
The pull in winding assesses generator output, and when it is higher than battery voltage, it pulls on the flipper closing the contacts and connecting the gen to battery.
All current flows through the fat winding, causing additional closing power on the contacts. (hold in winding)
If the gen slows down, its output is lower than the battery. The current reverses through the hold in winding and the magnetic force is in opposition to the pull in winding, and the points open, preventing discharging when going slow, or shut off.
The other unit is field control. It is always "on" when the tractor is shut off, the contacts are closed grounding the field. The field gets its volts on these units from the armature brush connected to the Armature terminal, and thus are dead when the cutout is open) As the gen turns, the field poles supply enough magnetism to pull in the cutout. This also makes enough voltage to ad to the field current, through the contacts to ground. As good charging voltage is reached, the field control contacts begin to chatter clipping the field voltage to limit the charging. When the field contacts are momentarily open, a resistor is then connected to ground allowing enough charging to keep the battery up. Though almost always chattering to controll charge rate, they can open all the way and let the resistor take care of the charge rate.
Comon issues are poor contact VR ground, poor generator ground, point cleanliness, moisture, broken wires, or bad external wires. Many Vrs are now made off shore, and are not reliable. I hope this helps. Jim

The original delco or autolite regulator worked very well for decades. the new imports are very poor. try to get an oem.

Cool, great explanation Jimbo, I enjoyed reading it. What you call the "pull in winding" (a good term to help one understand) I sometime refer to as (Im sure you know) the "shunt winding" as its across the cutout (GEN/ARM terminal) to ground, and as you say small wire as its relatively low curent as compared to the "hold in" I sometime refer to as the "series winding" and as you say big wire as its in series with the gennys output and may carry 20 amps. Its my understanding the reverse cutout current and the resulting opposite magnetic field is what helps drive open and unlatch the cutout relay.

I was thinking perhaps when the cutout closes and the series hold in winding is latching the relay, the shunt pull in winding drops out of the circuit??? you know for sure???? It would take a single pole double throw relay action to accomplish that but thats not rocket science, I need to take one apart or look at a diagram I reckon?????????????????????????

I agree the quality of Chinese made VR's isnt too great.

We need to meet up at a tractor show and swap a few big ones, maybe consume an adult beverage such as a barley soda, bring Bob M with you, we will gang up on him lol I outweigh him but bet he can outrun me !!!!

John T

For all the rest of us, it means "keep your receipt when you buy a VR", cause it ain't gonna last long.

Gordo

(quoted from post at 17:18:41 05/10/10) Cool, great explanation Jimbo, I enjoyed reading it. What you call the "pull in winding" (a good term to help one understand) I sometime refer to as (Im sure you know) the "shunt winding" as its across the cutout (GEN/ARM terminal) to ground, and as you say small wire as its relatively low curent as compared to the "hold in" I sometime refer to as the "series winding" and as you say big wire as its in series with the gennys output and may carry 20 amps. Its my understanding the reverse cutout current and the resulting opposite magnetic field is what helps drive open and unlatch the cutout relay.

I was thinking perhaps when the cutout closes and the series hold in winding is latching the relay, the shunt pull in winding drops out of the circuit??? you know for sure???? It would take a single pole double throw relay action to accomplish that but thats not rocket science, I need to take one apart or look at a diagram I reckon?????????????????????????

I agree the quality of Chinese made VR's isnt too great.

We need to meet up at a tractor show and swap a few big ones, maybe consume an adult beverage such as a barley soda, bring Bob M with you, we will gang up on him lol I outweigh him but bet he can outrun me !!!!

John T

Click to expand...

o, john, both remain active....I have "unwound" a few.

"I was thinking perhaps when the cutout closes and the series hold in winding is latching the relay, the shunt pull in winding drops out of the circuit??? you know for sure???? It would take a single pole double throw relay action to accomplish that but thats not rocket science, I need to take one apart or look at a diagram I reckon????????????????????????? "

The reverse series current & associated field has to overcome the shunt field before drop out.

The pull in winding is to ground and supplied from the Arm post. This keeps on keeping on for the duration. (other wise it would not pull in at the beginning) The arm voltage increases with RPM as the magnetism increases (due to the field windings tapping into the near open armature voltage, the field force almost is equal to full running current) the only thing "attached" to the arm is the pull in winding. Gotta Love it. Oldtyme Electrical compromise. Jim

I will add the other aspect to short life of a voltage regulator. Now days, one generator fits all or nearly all of the old farmall tractors when in reality the ones that came from factory with a high low charge switch had an entierly different current flow through the field coils than the models that came with voltage regulator. I have been cussing rebuilt generators since their inception as they don't match the original equipment. I used to always use genuine delco remy parts to repair generators is at all possible. If a generator came into the shop that was a rebuilt unit, then I normally just sold another rebuilt one as you could not match parts to fit a good share of the time. Wrong field coils, armature turned down to nothing, shafts cut for undersize bushing, wrong brushs etc. Way too much current flowing through most of the voltage regulator vibrating contacts to sustain clean contact surfaces for long. Once I had a new 706 that was eating up voltage regulators, and this was back when they made good 3 unit regulator, the voltage out put was eratic which of course could not be detected very well by the owner as it had an idiot lamp, no ammeter. I took generator apart and found that the current flow through field coils matched a 6 volt generator , all other parts were correct. Replaced field coils, problem solved.

Here is a simple but excellent wiring diagram of the voltage regulator circuit. Shows just exactly what"s in there.

They fail because generators have not replaced with alternators. Since mine were replaced I've not had to change a single one.