Need some electrical help with my ‘68 Plymouth Valiant 100

[66fs]

Lesson #1: Only do one thing at a time and take "before" pictures.
Lesson #2: Don't throw anything away for your car.

First, since you are just beginning, don't make any changes to your car yet. Use the correct parts for your car. It gets confusing at first. Safety first. Brakes. There should be tell tale signs of fluid somewhere. Inside where the master cylinder is bolted to the firewall, out of the drums, brake lines, or wheel cylinder bleeders. This is not rocket science, you can do it. Old is better than new. Rebuild what you can, buy what you need. Skip new brake hardware, some of it is absolute junk. Drums will work fine for most people. You should be able to get it going for little money. Let us know what you find...

New voltage regulators are solid state and should take your factory connectors and even the factory cover.
Have a parts store test the alternator. Next clean connectors (one at a time) and coat with dielectric grease to prevent corrosion before reinstalling. Make sure connections are tight. Same for grounds.

 

[LO23M8B]

Agree with all the above. Putting in a new good hi amp battery goes a long way also.

 

[snailgarden]

In my opinion.

If you are driving the car the brakes are #1

The water leak may or may not be an eminent issue. IF coolant is getting into the oil that would be a bigger issue than just leaking out.

The electrical needs better diagnosis. If the alternator being sent is a direct replacement, swapping that is easy and will rule out the alternator as a cause.

There are a lot of what if's here.

So let us know some of the answers

1. Are you driving the car.
2. Is coolant getting into the oil

So I added more brake fluid, pumped the brakes like crazy, but I don’t think I’m seeing anything leaking out of the back wheels, so I’m slightly confused on what is wrong.

 

[67Dart273]

So I added more brake fluid, pumped the brakes like crazy, but I don’t think I’m seeing anything leaking out of the back wheels, so I’m slightly confused on what is wrong.

Detail exactly what the brakes do and don't do. Are these front disk or drums?

 

[snailgarden]

Detail exactly what the brakes do and don't do. Are these front disk or drums?

Drum brakes. I checked the brake fluid and the front half of the master cylinder os completely gone. So most likely something is wrong with the rear drums, or at least that’s what I assumed. I filled it with brake fluid and tried pumping the brakes to see if I could find leaking from the rears, but I couldn’t seem to find the leak.

 

[LO23M8B]

Do you see any streaking on the inside of the rear backing plates? Look under the car on the inside of the brakes and tires.

Drum brakes. I checked the brake fluid and the front half of the master cylinder os completely gone. So most likely something is wrong with the rear drums, or at least that’s what I assumed. I filled it with brake fluid and tried pumping the brakes to see if I could find leaking from the rears, but I couldn’t seem to find the leak

 

[MDchanic]

So I added more brake fluid, pumped the brakes like crazy, but I don’t think I’m seeing anything leaking out of the back wheels...

Pumping isn't what you need to do.

You need to pump initially, to load as much fluid into the lines as will fit.
Once you get a firm pedal, you need to lean on it, HARD, with all your strength.
If you have power brakes, you need to do it with the engine running, so that the booster is boosting.

With hard, steady pressure, even if there is some air in the lines, you should arrive at a point where everything is as compressed as it can be, and, even if the pedal doesn't get truly hard because of air in the system, the pedal should stay firmly in one position and shouldn't slowly sink down.

If the pedal sinks, you've either got a leak or a bad master cylinder.
Pump it up again, and repeat. After a few cycles, there should be a lot of brake fluid on the ground somewhere. If there isn't, then you have a bad master cylinder.

By the way, how long was this car sitting before you got it?

– Eric

 

[67Dart273]

Drum brakes. I checked the brake fluid and the front half of the master cylinder os completely gone. So most likely something is wrong with the rear drums, or at least that’s what I assumed. I filled it with brake fluid and tried pumping the brakes to see if I could find leaking from the rears, but I couldn’t seem to find the leak.

You will have to bleed them and may have to prime the master cylinder. Google search, there are different ways to do so. I think it is also in the service manual. If there is no evidence of leakage in the carpet or down the firewall, you most likely have a leak in the tubing to the rear, and could be "anyplace from the master on back. By the way the FRONT fitting on the master feeds the REAR brakes.

 

[snailgarden]

Pumping isn't what you need to do.

You need to pump initially, to load as much fluid into the lines as will fit.
Once you get a firm pedal, you need to lean on it, HARD, with all your strength.
If you have power brakes, you need to do it with the engine running, so that the booster is boosting.

With hard, steady pressure, even if there is some air in the lines, you should arrive at a point where everything is as compressed as it can be, and, even if the pedal doesn't get truly hard because of air in the system, the pedal should stay firmly in one position and shouldn't slowly sink down.

If the pedal sinks, you've either got a leak or a bad master cylinder.
Pump it up again, and repeat. After a few cycles, there should be a lot of brake fluid on the ground somewhere. If there isn't, then you have a bad master cylinder.

By the way, how long was this car sitting before you got it?

– Eric

Got it, I will try that out and see what happens.

Sorry to go back and forth, but got the three fuse head connectors that go into the fire way cleaned and used diaelectric grease on them and unfortunatley, the flickering is still happening. I had shard a photo of the fuse box earlier in this thread and you had reposted it with arrows. Is that red arrow pointing to the fusible link? It’s a black wire and red wire with a connection in between them next to the fuse heads.

 

[snailgarden]

You will have to bleed them and may have to prime the master cylinder. Google search, there are different ways to do so. I think it is also in the service manual. If there is no evidence of leakage in the carpet or down the firewall, you most likely have a leak in the tubing to the rear, and could be "anyplace from the master on back. By the way the FRONT fitting on the master feeds the REAR brakes.

Thanks I’ll look into bleeding the brakes. I got a service manual on the way too, so that’ll be very helpful once It’s here. I am aware that the front fitting in the master cylinder is for the rear, and that is the one that is empty.

 

[snailgarden]

Pumping isn't what you need to do.

You need to pump initially, to load as much fluid into the lines as will fit.
Once you get a firm pedal, you need to lean on it, HARD, with all your strength.
If you have power brakes, you need to do it with the engine running, so that the booster is boosting.

With hard, steady pressure, even if there is some air in the lines, you should arrive at a point where everything is as compressed as it can be, and, even if the pedal doesn't get truly hard because of air in the system, the pedal should stay firmly in one position and shouldn't slowly sink down.

If the pedal sinks, you've either got a leak or a bad master cylinder.
Pump it up again, and repeat. After a few cycles, there should be a lot of brake fluid on the ground somewhere. If there isn't, then you have a bad master cylinder.

By the way, how long was this car sitting before you got it?

– Eric

Sorry I realize I didn’t fully respond to this all. It wasn’t being driven as a daily driver as of recently, but the previous owner’s dad would move the car around so it wasn’t just stationary, I’m not sure how much he was actually driving it, though. I know the son (previous owner) used to drive it as his daily driver when he first got it in 2014 and unsure how long he drove it around for.

Also I don’t know if this is helpful, but I’ve noticed around the master cylinder there is splatter spots of what I’m assuming might be brake fluid. Is it possible that could be an indication that the master cylinder is bad?

 

[MDchanic]

Sorry to go back and forth, but got the three fuse head connectors that go into the fire way cleaned and used diaelectric grease on them and unfortunatley, the flickering is still happening. I had shard a photo of the fuse box earlier in this thread and you had reposted it with arrows. Is that red arrow pointing to the fusible link? It’s a black wire and red wire with a connection in between them next to the fuse heads.

Wrong guy. That was a different poster.
It can be hard to keep the various characters straight without a libretto.
But, yes, I believe that was where he indicated the fusible link was.
The fact that anything is working indicates that the fusible link didn't fuse.
If you wiggle it and it doesn't affect the flickering, then it's not the problem.

Sorry I realize I didn’t fully respond to this all. It wasn’t being driven as a daily driver as of recently, but the previous owner’s dad would move the car around so it wasn’t just stationary, I’m not sure how much he was actually driving it, though. I know the son (previous owner) used to drive it as his daily driver when he first got it in 2014 and unsure how long he drove it around for.

"Was a daily driver in 2014" + "Dad used to move the car around" = "Car hasn't moved in ten years" (give or take).

A car that hasn't moved in ten years will almost definitely need a master cylinder and wheel cylinders. If you can get it going by replacing only one or two, you will be replacing the rest soon.
You're in the desert (at least compared to here), so you may not need to replace the brake lines, but then again, you may.

... I’ve noticed around the master cylinder there is splatter spots of what I’m assuming might be brake fluid. Is it possible that could be an indication that the master cylinder is bad?

As they say in the car business, "They all do that."
Then again, as they say on the interwebs, "This is useless without pictures."
But it's probably normal.

Definitely give a go at bleeding it, if you're game to now (you probably don't need to bleed it in order to prove it's no good, but you do in order to prove that it is good).
Just remember that bleeders break off (usually the easiest fix then is to just replace the wheel cylinder) and other bad things happen, so be prepared.
Remember, after you bleed it, if you can't stand on that pedal and have it feel hard as a rock, there's something wrong.

Also, be aware that in order to bleed the brakes properly, in spite of all kinds of modern geegaws that claim otherwise, you'll need another person (generally a cranky and impatient significant other), so plan ahead.
Also also, you really need to have a set of flare nut wrenches to start messing with the brakes, if you don't already.
Finally, in spite of having the aforementioned flare nut wrenches, you will also need a small (6") curved-jaw Vise-Grip and a sledgehammer – Brake fittings are generally at least somewhat rusted on, and they tend to respond to sharp shocks much better than steady pulls. This means that using a wrench, even a flare-nut wrench, will often just round the fitting. The (very indelicate) way to avoid this is to clamp that small Vise-Grip onto the nut once, as hard as you can, and then strike it sharply with a sledgehammer to break it free. After that, you remove the Vise-Grip and use a wrench. Always spray liberally with penetrating oil and allow to sit (ideally for a few days) first (I like KROIL, others like other brands). If removing brake line fittings, once you break it free, DO NOT keep turning the nut – spray it again and watch it while moving it back and forth repeatedly. If it is rusted to the brake line, wiggling it back and forth gently, with plenty of penetrating oil, will usually allow it to work free without twisting then end of the line off.

As I noted in an earlier post, you will need to place your jackstands under the unibody frame members if you want the rear axle to hang low, which you do want if you are messing with the bleeders, so you have room to work.

– Eric

 

[MDchanic]

And one other thing. I don't think this was mentioned yet.

If your car is a '68, then it came from the factory with left-handed lug nuts on the left (driver's) side of the car.

That means they come off clockwise.

You can tell by looking at the ends of the studs: The ones on the left will have an "L" stamped into them. (You may need to use a wire brush to see).

If you turn them clockwise, and you are persistent, you will have a bad day.

– Eric

 

[ESP47]

Got it, I will try that out and see what happens.

Sorry to go back and forth, but got the three fuse head connectors that go into the fire way cleaned and used diaelectric grease on them and unfortunatley, the flickering is still happening. I had shard a photo of the fuse box earlier in this thread and you had reposted it with arrows. Is that red arrow pointing to the fusible link? It’s a black wire and red wire with a connection in between them next to the fuse heads.

That thing is called a bulkhead connector. Your fuse box is under the dash on the driver side. The bulkhead just allows wires to pass through the firewall to the interior. Congrats on getting the bulkhead connectors off without breaking them. No small feat on an old car.

I'd tackle your other problems while you wait for your alternator to come in. The fact that it failed its test at the parts store is pretty telling. Probably not worth the energy to pour through all the other troubleshooting steps if you already know the alternator is bad. Unless you're just looking to learn...which is always a good thing.

 

[Dana67Dart]

Sorry to go back and forth, but got the three fuse head connectors that go into the fire way cleaned and used diaelectric grease on them and unfortunatley, the flickering is still happening. I had shard a photo of the fuse box earlier in this thread and you had reposted it with arrows. Is that red arrow pointing to the fusible link? It’s a black wire and red wire with a connection in between them next to the fuse heads.

The red arrow points to the actual fusible link.

This is what it looks like not attached to anything. (NOTE: there is a tab on the wire that says FUSABLE LINK) in your case the wire looks black and the tab looks yellow.

You need to understand that the entire wire is a fuse. the TAB is only there as an indicator.

I know it has been mentioned before but terminology means a lot.

This is The "Bulkhead" all the wires inside the car connect to it under the dash

These are the Bulkhead Connectors. all the wires in the engine compartment and the forward lighting are connected to them. They connect to the bulk head.

There are NO fuses in the Bulkhead EXCEPT the Fusable Link which is attached to it.



This is the "Fuse Block" it is mounted under the dash by the Emergency brake. SOME fuses are powered some are only powered when something is on

 

[snailgarden]

The red arrow points to the actual fusible link.
View attachment 1716332137

This is what it looks like not attached to anything. (NOTE: there is a tab on the wire that says FUSABLE LINK) in your case the wire looks black and the tab looks yellow.

You need to understand that the entire wire is a fuse. the TAB is only there as an indicator.
View attachment 1716332136

I know it has been mentioned before but terminology means a lot.

This is The "Bulkhead" all the wires inside the car connect to it under the dash
View attachment 1716332142


These are the Bulkhead Connectors. all the wires in the engine compartment and the forward lighting are connected to them. They connect to the bulk head.

View attachment 1716332143

There are NO fuses in the Bulkhead EXCEPT the Fusable Link which is attached to it.



This is the "Fuse Block" it is mounted under the dash by the Emergency brake. SOME fuses are powered some are only powered when something is on

View attachment 1716332145

Thank you so much for this. This just helped a ton.

I’m having some confusion regarding the VR again, because I’m looking at some original VR’s and some are adjustable, but I don’t fully understand if mine is, or how would I exactly know it is? What is different on it?

 

[snailgarden]

The red arrow points to the actual fusible link.
View attachment 1716332137

This is what it looks like not attached to anything. (NOTE: there is a tab on the wire that says FUSABLE LINK) in your case the wire looks black and the tab looks yellow.

You need to understand that the entire wire is a fuse. the TAB is only there as an indicator.
View attachment 1716332136

I know it has been mentioned before but terminology means a lot.

This is The "Bulkhead" all the wires inside the car connect to it under the dash
View attachment 1716332142


These are the Bulkhead Connectors. all the wires in the engine compartment and the forward lighting are connected to them. They connect to the bulk head.

View attachment 1716332143

There are NO fuses in the Bulkhead EXCEPT the Fusable Link which is attached to it.



This is the "Fuse Block" it is mounted under the dash by the Emergency brake. SOME fuses are powered some are only powered when something is on

View attachment 1716332145

Also, how do I test these fuses? I’m assuming I pull them out one by one, but how do you suggest actually making sure they work (besides if they are broken)?

With the bulkhead under the dash, would I just pull out the bulkhead connectors and use the contact cleaner and diaelectric grease on those? I did this to the ones right on the firewall that I took a picture of, but not these ones under the dash.

 

[Dana67Dart]

I’m having some confusion regarding the VR again, because I’m looking at some original VR’s and some are adjustable, but I don’t fully understand if mine is, or how would I exactly know it is? What is different on it

There are purposefully adjustable voltage regulators and ones that are adjustable but only to correct manufacturers errors.

This is an example of a non adjustable electro mechanical VR. Note that it looks like the one you have now and it has the wire would resisters underneath it.

This is an example of a non adjustable Electronic version of the one you have. Note there are no wire wound resisters underneath. It also looks like the one you have now.

This is also a non adjustable electronic version of your VR, it does not look like yours but will work just fine.

Adjustable versions exist and have a place to put in a screwdriver to turn a screw that will change the voltage set point.

You do not need one of those. Any of the ones above will work fine.

Also, how do I test these fuses? I’m assuming I pull them out one by one, but how do you suggest actually making sure they work (besides if they are broken)?

Testing fuses is both visual and functional.

Visual... Is the wire inside the glass tube intact?

Functional... When there is voltage on one side of the fuse is there voltage on the other? This is best done under load, like the fuse for the cigarette lighter, test with the cigarette lighter pressed in like your going to have it heat up.

With the bulkhead under the dash, would I just pull out the bulkhead connectors and use the contact cleaner and diaelectric grease on those? I did this to the ones right on the firewall that I took a picture of, but not these ones under the dash

The metal terminals in the bulkhead and bulkhead connectors are accessable in the engine compartment. If you disconnected the bulkhead connector and cleaned the metal terminals in the part with the wires attached to it and the metal terminals inside the bulkhead on the firewall you cleaned it correctly.

Some times the female part needs to have the parts punched SLIGHTLY .

Press on the red arrow part of the terminal to move the curved parts SLIGHTLY (green arrows) this makes a tighter contact to the male part of the terminal.

Be sure to go back and watch the videos I posted about alternators and voltage regulators.

 

[MDchanic]

I’m looking at some original VR’s and some are adjustable, but I don’t fully understand if mine is, or how would I exactly know it is? What is different on it?

You have an original, non-adjustable, mechanical voltage regulator:

It looked like this when it was new:

An original, adjustable mechanical voltage regulator looks like this:

Older regulators are "mechanical," because they use sets of physical magnetic coils and electrical contacts, which move, in order to rapidly turn the alternator field coils on and off, which regulates the overall average voltage, but which creates a voltage that varies from one millisecond to another.
They work fine in their original applications, but, since they involve physical objects with mass moving through space, are inherently prone to wear and ultimate failure.

Modern regulators are "electronic" or "solid state," and have no moving parts.
They work through electronic components, provide smoother regulation, are less likely to fail (provided they are made well), and are cheaper to manufacture in the modern era.

Yours is mechanical and could be bad. It could also be fine. One way of testing it is to replace it with one that works. (In the old days, these were "toolbox items" at the junkyard – things that you'd throw into your toolbox, and, in a sort of a "Don't ask, don't tell" exchange, you wouldn't cop to having them, and the yard owner wouldn't care that you took them. Every single car had one, and any sensible person would replace a bad one with a new one, so they had very little value, but were generally useful if you needed to troubleshoot a problem like yours.).
Nowadays, if you don't have one, you'd need to buy one for fifty bucks, unless you've got a buddy with a good-running MoPar, in which case you could just swap them out and see whether your problem goes away.

Also, how do I test these fuses?

If they're blown, the inside of the glass is black and the little wire thingy is melted.

You can also just pull each one out and test continuity with an ohmmeter. There should be no resistance.

– Eric

edit: Damn. Beat me to it by one minute. Guess I have to get up earlier.

 

[Dana67Dart]

Eric

Can't sleep either!

 

[Dana67Dart]

edit: Damn. Beat me to it by one minute. Guess I have to get up earlier

You added complimentary info that I did not.

Great minds think alike!

 

[MDchanic]

You added complimentary info that I did not.

Great minds think alike!

And vice-versa.

I don't consider myself an expert, but I do think things through when the old thinker is working, and I have a bit of a soft spot for helping people who are new to this (as opposed to opinionated jerks who should already know whatever they're asking and are just looking to have their unsubstantiated opinions confirmed, which is pretty much 99.9% of the internet), so I'm trying to provide fairly comprehensive answers where I can.

Your links to the Master Tech filmstrips are great. I love those things, and they really do explain things both well and simply. Same reason I used to enjoy reading old factory service manuals when I was a kid - they explain whatever it is clearly, so that you can then think for yourself and figure out the problem (unlike the checklist-flowcharts that started to show up in the mid-seventies).

My advice to SnailGarden would be to bookmark the whole Master Tech series (it's in MyMopars, I believe) and watch / read them all over a few weeks, and also to take the time to sit and read her Service Manual explanations of whatever she needs to work on, as this stuff is invaluable.

A number of years ago, I went way down the rabbit hole and spent way too much time making way too many posts on another forum for another make, and had to just quit cold turkey, so I will try to avoid getting too involved here.

- Eric

 

[snailgarden]

There are purposefully adjustable voltage regulators and ones that are adjustable but only to correct manufacturers errors.

This is an example of a non adjustable electro mechanical VR. Note that it looks like the one you have now and it has the wire would resisters underneath it.

View attachment 1716332272
This is an example of a non adjustable Electronic version of the one you have. Note there are no wire wound resisters underneath. It also looks like the one you have now.

View attachment 1716332273

This is also a non adjustable electronic version of your VR, it does not look like yours but will work just fine.

View attachment 1716332281
Adjustable versions exist and have a place to put in a screwdriver to turn a screw that will change the voltage set point.

You do not need one of those. Any of the ones above will work fine.



Testing fuses is both visual and functional.

Visual... Is the wire inside the glass tube intact?

Functional... When there is voltage on one side of the fuse is there voltage on the other? This is best done under load, like the fuse for the cigarette lighter, test with the cigarette lighter pressed in like your going to have it heat up.






The metal terminals in the bulkhead and bulkhead connectors are accessable in the engine compartment. If you disconnected the bulkhead connector and cleaned the metal terminals in the part with the wires attached to it and the metal terminals inside the bulkhead on the firewall you cleaned it correctly.

Some times the female part needs to have the parts punched SLIGHTLY .

Press on the red arrow part of the terminal to move the curved parts SLIGHTLY (green arrows) this makes a tighter contact to the male part of the terminal.

View attachment 1716332282


Be sure to go back and watch the videos I posted about alternators and voltage regulators.

Thank you you and MDchanic have been a huge help through this and I appreciate how patient you guys are.

I did watch those videos also, and this may be dumb of me so I am sorry in advance, but when I was searching for VR’s on Google I noticed it said for my specific valiant 100 with the 4.5 L 273 v8, that it actually would use a 60 amp VR. I was going to but one that was the 35 and 46 one. So, should o get the 60 amp one instead?

Also this may be another dumb question after all of this knowledge you guys dropped, but does the amperage on your voltage regulator match the amperage on your alternator? I would assume it would. I’m going to check to see the stamp on my alternator once I’m back home for the parts number and the listed amp

 

[snailgarden]

And vice-versa.

I don't consider myself an expert, but I do think things through when the old thinker is working, and I have a bit of a soft spot for helping people who are new to this (as opposed to opinionated jerks who should already know whatever they're asking and are just looking to have their unsubstantiated opinions confirmed, which is pretty much 99.9% of the internet), so I'm trying to provide fairly comprehensive answers where I can.

Your links to the Master Tech filmstrips are great. I love those things, and they really do explain things both well and simply. Same reason I used to enjoy reading old factory service manuals when I was a kid - they explain whatever it is clearly, so that you can then think for yourself and figure out the problem (unlike the checklist-flowcharts that started to show up in the mid-seventies).

My advice to SnailGarden would be to bookmark the whole Master Tech series (it's in MyMopars, I believe) and watch / read them all over a few weeks, and also to take the time to sit and read her Service Manual explanations of whatever she needs to work on, as this stuff is invaluable.

A number of years ago, I went way down the rabbit hole and spent way too much time making way too many posts on another forum for another make, and had to just quit cold turkey, so I will try to avoid getting too involved here.

- Eric

You guys have been incredibly helpful, thanks so much for this. Still waiting on my service manual too, hopefully it gets here soon but maybe won’t until after Thanksgiving.

I asked some questions above in response to danadart’s reply, but wondering if my car would actually need a 60 amp VR instead of the 35 and 46 one, also in general does the VR amp and alternator amp match?

 

[MDchanic]

The alternator makes and alternating electric current (AC), but the car uses non-alternating current (DC).
It is cheaper and easier to make generators for AC than it is for DC, and they work better, so that's what they use now (before the advent of small, reliable, cheap diodes, this wasn't the case, so before the early '60s, cars used DC generators).
It's an example of a genuine technological improvement. They happen.

Alternators, generators, and electric motors (fan motor, starter motor, your vacuum cleaner, cordless drills) all work on the same principle, that a magnetic field crossing a coil of wire makes an electric current (or an electric current acting on a magnet creates force). Some motors or generators are "permanent magnet" types, which get their magnetism from regular old magnets, they type that hold the kitchen cabinets closed, or whatever. Magnet technology has genuinely improved as well over the past few years, so now you can have strong permanent-magnet motors and generators (all those "Brushless!" DeWalt / Milwaukee / Makita cordless drills, etc.), but in the "good old days," permanent-magnet motors and generators were crap because the magnets just weren't strong enough (I suspect it's why the cordless-drill folks advertise "Brushless!" rather than "Permanent Magnet!").

So, all factory-original alternators that I know of (there are some permanent-magnet aftermarket motorcycle alternators now) use electromagnets to make their electricity.
The alternator has a rotor and a stator.
The rotor rotates, the stator stays still.
The windings of the rotor are connected to the outside world with carbon brushes (actually, chunks) that press against brass commutator rings.
When you start the car, the regulator allows a bit of "exciter" current to flow through the rotor, which creates initial magnetism, and as the alternator spins it begins to make current from the stator windings, and the voltage increases.
Once the voltage reaches the regulator's setting (about 13.5 to 14.3 volts), the regulator starts to regulate, limiting the current it feeds to the rotor through the brushes.
Less rotor current = less rotor magnetism = less current generated (alternated?).
You turn on the headlights or the blower, voltage goes down, rotor current goes up, voltage goes back where it should be.
Motor revs faster, voltage goes up, rotor current goes down, voltage goes back where it should be.
You get it.

In our context (I am not an electrical engineer), an alternator with a higher output will need to draw more current for its rotor ("Field Current"), so a regulator designed for a 30A alternator probably won't work (for very long) with a 60A alternator.
HOWEVER, a regulator for a 60A alternator should work just fine for a 30A alternator, as it will feed just enough current to achieve the desired voltage.
Because of this, the average parts supplier, rather than make two different regulators (which both cost the same to make), will just make one, specified as 60A, but it will work for both 30 and 60A alternators.

So a 60A regulator that is otherwise the same should work fine.

BUT, as an aside, using a 60A alternator in a car designed for a 30A alternator could cause trouble ("trouble" = "fire") because the car's charging wiring, including wiring to the ammeter in the dash, is not large enough to handle the increased current.
But that's a subject for about a hundred other pre-existing threads.

- Eric