Hey Guys,
Does anybody have any info on how an old school mechanical voltage regulator works? And how to go about testing it to confirm that it's working properly? I don't have a specific application, I'm just curious. You never can have too much information, even on old outmoded stuff.
Thanx,
TR

I'm not sure how they work, I guess through resistance. Doc would have known.
Here's to you Doc We miss you.
Shane

i'm an old fart, but i worked on a lot of those in the 60s-70s. DISCLIMER: i'm digging this out of my distant memory in a foggy part of my brain.

if you take the cover off of one of those regulators there will be 2-3 sets of points under there, the points will make and break contact by way of coils of fine armature wire under the points (they are like mini-solenoids). there are 4 terminals (or a plug with 4 wires) thes sense battery voltage- B+, ign on/ off-i terminal, a field terminal-F, and an idiot light terminal.

all of the old (actually ALL) of the alternator systems work the same way, when you put battery voltage to the field the alternator will put out full output-this can be 16+ volts. when you disconnect the battery from the field the alternator will put out 0 volts. voltage can be varied by how fast the points cycle in the regulator. the actual figure you are looking for with a CHARGED BATTERY is 13.8-14.2 volts. with a low battery the voltage will be considerably higher, right after start the voltage will be higher, the voltage is regulated by the the voltage input by the 3 out of 4 terminals on the voltage regulator and the time differential of open/closed points between the battery and field.

there are 2 common failure modes on a mechanical regulator"
1-a break in the fine armature wire that controlls the points, this will result in 0 charge.
2-pitted points in the regulator, this usually results in the points sticking and you will get a 16+ volt charge, or just erratic readings.

checking for a bad regulator, you do that indirectly:
1-fully charge the battery and hook a voltmeter to it, it should read 12.5-12.8 volts.
2- start the car and look at the voltage on the voltmeter, it should read 13.8 14.2 after stabalizing.
3-if it reads around 16, replace the voltage regulator.
4-if it reads 12, unplug the regulator and jump from the battery to the field terminal.

A-if the voltage jumps to around 16 replace the voltage regulator.
B-if the voltage stay at 12 replace the voltage regulator and alternator (you could just replace the voltage regulator but if the regulator was allowing the alternator to charge at 16 V and it burned out it will damage the new regulator.
these are just the rules for mechanical regulators and have no correlations to todays charging systems.

the plug i referred to above was for ford regulators, they were marked B-2-3-4, you would use a (floyd) cotterpin to jump between the B and 3 terminals to supply bat voltage to the field terminal.

even going further back, to the days of generators, does anybody remember those little instruction sheets that said you had to polorize the generator by useing a jumper and strike a spark between the B and A terminal???

"....i'm an old fart, but i worked on a lot of those in the 60s-70s. DISCLIMER: i'm digging this out of my distant memory in a foggy part of my brain......"

Me too

Your explanation sounds right from what I remember. And yes I remember them, never read them just knew you had to do it. Even remember why. A generator is self energizing, but relies on a slight magnetic field in the housing to get started. Polarizing sets up that field.

A few years ago I was doing a fair amount of work on old Harleys had a couple brought in by guys who had changed their generators but still wouldn’t charge. I polarized them and cured the problem. They were pretty amazed about what could be done with a jumper wire

the regulator with 3 relays is for a generator

the extra relay will connect the output of the generator to the battery when the generator has voltage on its output
alternator doesnt need this it has diodes that do the same thing.
But the alternator is always connected to the battery thru the diodes.
This is why theres a fuseable link (diodes can fail to a short)

the other two relays the one with very fine wire senses the battry voltage and will stop the charge at 14v or so.

the one with the larger wire feeds more voltage to the feild if the output tapers off.

these regulators very rarly fail and can usually be ajdusted for more or less charge or voltage.. the real old one have screws for adjustments.. the newest youve got to bend the tabs on the springs and contacts.

To fix these a point file and a burnishing tool is all thats required.

to fix a new electronic one a trash can and a new part is the only way possible. they are sealed and potted.

alternators have only brushes and bearings as moving parts they can be fixed with either of these.

older alternators have diodes that can be replaced and an external regulator( sometimes the relay kind)

newer alternators may be an all in one (brush diode electronicpack) that can be replaced as a unit.

Super answers, guys! It's always good to sit back and listen to the experienced. This forum never ceases to amaze me with the wealth of knowledge of its subscribers!
Thanx Again,
TR

hey 1957 plymouth hemi, your brain isn't to foggy. you are exactly right.
AND i had a couple of those old generator harleys, one had that BIG delco-remy regulater and one had that little squre bosch regulater.

Great explanations guys, gotta hand it to ya'll

Vince

sorry for dragging up an old topic.. but I've got a problem relating to this:

I've got a 1949 fiat topolino with a mechanical regulator with three relays inside and a resistor on the back. basically, I keep getting carbon built up everywhere, on the generator commutator, and on the middle relay.
at idle all the relays stay closed, but if I rev it up two of them start to cycle together, one with low-current looking points on it, and one with fat ones.
the one with fat points sparks every time it cycles, I think this is part of the problem as thats the one which cuts the voltage back if it goes above about 13.8v. after about half an hour of driving it stops making contact through the carbon that's built up and my battery light comes on, cleaning it with fine sand paper gives me another half hour.

what would cause this problem? have I got a short or partial short somewhere which is causing too much current to go through that relay?

I'm thinking that the "carbon build-up" is being caused by current arcing.
Perhaps one of the sets of contacts are not properly adjusted. (Some voltage regulators were adjustable, some weren't.)

A certain amount of carbon on the armature itself would be normal ... as that is just the brushes wearing. Check the spring tension and the remaining length of the carbon brushes. If there's a problem there, it might lead to intermittent output from the generator itself. I would think that the regulator would be expecting to see fairly consistent output from the generator, and if it wasn't ... it would be working overtime trying to do it's job.

Here's a link to basic operation.

thanks for the reply,
I had the commutator machined not too long ago, and it continued to eat through my brushes, the spring tension is good, and the brushes are new (again), my regulator is adjustable with screws to move the points closer or further apart, how do I go about setting the adjustment?
dont be afraid I wont understand something, I've worked with electronics for most of my life.

Sorry, I've been away from the site for a while.

I'm now wondering what kind of draws you have on this electrical system?
I would imagine that a stock 1949 generator-equipped vehicle was designed to support a very low (by modern standards) electrical load. Headlights, signal lights, perhaps a blower motor and windshiel wipers.

If you've added a lot of new loads ... say a killer sound system with a subwoofer or heated leather seats ... there's no way that poor old generator will be able to keep up.

Hey Phreak, I'm a retired Electonics Engineer (career three, colleges took A LOT of my income), and grew up spinning a wrench. First the commutator... Sometimes machining it just doesnt work as it has wore beyond useful life. The smaller it's diameter the greater the lagtime btween the brush being in contact with more than one of the contacts which is the base cause of arcing and carbon build up. the second thing with the commutator is was it machined right? It isn't a simple matter of turning it on a lathe, bevels need to be cut on each side of the contacts, first to ensure a clean area, second to reduce the time that your brushes spent on two contacts at once, the greater this time is, the more arcing that occurs, just as you notice in an old well worn electric hand drill. A good shop will also rebed these contacts with a good epoxy such as acraglas to ensure none break loose, and to ensure proper insulation between each and every one. SADLY, this is a dying art, in this day of throwaways and factory only rebuilding, really messsing with those of us who use or need the proper parts. On to your regulator, one forum member posted the most probable problem, that being misadjusted contacts. HOWEVER knowing how many of these contact were designed, I can tell you that carbon buildup can also be caused by contacts that are beyond their lifespan. These were typically domed silver or silver clad contacts, the silver was used as it minimized arcing and silver oxide and silver both have identical resistance/conductance characteristics. When the contacts wear flat (or are filed instead of burnished, which is a form of mechanical polishing that doesnt remove metal) A greater area where arcs form develop, and the more arcing that happens, more metal is burned away, reducing reliable contact area (think relay bounce characteristics) leading to more carbon build up and cascading arcing conditions. Hopefully with your knowledge and this information you can come up with a suitable cure for your problem.