Blowing voltage regulators

-
D

Dodge6719

Member
Joined
Aug 8, 2015
Messages
20
Reaction score
9
Location
Finland
I'm having trouble with my electro mechanical voltage regulator. In the past 4 years I have bought 3 and today I blew another one. I don't seem to get them to last more than a couple of thousand miles at the most.

I had to change the alternator about at the same time the first one blew but can't remember which one went first. Could this be the alternator causing this or something else? Where should I start looking for faults? Could this be solved with an electrical regulator that fits the single field alternator?

When the system has been working it has charged fine, no overcharging or anything it just gives up after a while.
 
I would first make sure you have a solid ground on the regulator and clean the connections to regulator and alternator use dielectric grease, then I would suspect China.
 
Dodge6719 said:
I'm having trouble with my electro mechanical voltage regulator. In the past 4 years I have bought 3 and today I blew another one. I don't seem to get them to last more than a couple of thousand miles at the most.

I had to change the alternator about at the same time the first one blew but can't remember which one went first. Could this be the alternator causing this or something else? Where should I start looking for faults? Could this be solved with an electrical regulator that fits the single field alternator?

When the system has been working it has charged fine, no overcharging or anything it just gives up after a while.
Click to expand...
What part(s) 'blew'?
 
When you talk electro mechanical are you talking original style where there are coils that make and brake a connection to the field?
 
Wiring is old! That said, think about it.

If all is to snuff these issues are rare. I run and electronic unit and single field Alternator that looks just like the old mechanical. All new wiring and no issues since 2014! Most of these issues are related to old tired wiring! It may look OK until you strip back the insulation and find lots of green and black!
 
Mattax said:
What part(s) 'blew'?
Click to expand...

Only the regulator, first time alternator of natural causes.

Dana67Dart said:
When you talk electro mechanical are you talking original style where there are coils that make and brake a connection to the field?
Click to expand...

This is the points type regulator

1969383S said:
Wiring is old! That said, think about it.

If all is to snuff these issues are rare. I run and electronic unit and single field Alternator that looks just like the old mechanical. All new wiring and no issues since 2014! Most of these issues are related to old tired wiring! It may look OK until you strip back the insulation and find lots of green and black!
Click to expand...

What harness did you use? Is there any premade kit that is plug and play or did you use an universal kit?

Going to go tinker with it as I got the new regulator, read somewhere about adding an additional ground wire to it, so I will try that and put an wire between the regulator and the engine block/firewall ground.
 
I would be with 1969383S and suspect wiring and/or a grounding issue.

I would buy a new VR Plug, as it may have bad connections INSIDE it where you can not see.....I have had this issue with a VR Plug before....looks good and may test good, but once you are driving the bad connections inside it jiggle from good to bad.

vrplug.jpg
 
Dodge6719 said:
Only the regulator, first time alternator of natural causes.

This is the points type regulator
Click to expand...
Sorry I wasn't clear.
Inside there is an electromagnet and a set of double points.
Underneath, there are resistors.
There's also a fuse wire.
Look at which one failed. This will be the first clue as to what went wrong.
 
Mattax said:
Sorry I wasn't clear.
Inside there is an electromagnet and a set of double points.
Underneath, there are resistors.
There's also a fuse wire.
Look at which one failed. This will be the first clue as to what went wrong.
Click to expand...

Aah ok, the points had welded themselves together. And then naturally the fuse wire.
The fuse wire runs on the inside between one side of the points to the resistor, correct? And there's one on both sides of the breaker points?
 
Dodge6719 said:
Aah ok, the points had welded themselves together. And then naturally the fuse wire.
The fuse wire runs on the inside between one side of the points to the resistor, correct? And there's one on both sides of the breaker points?
Click to expand...
Yes. correct.
There's a fuse wire for each. One for the upper contact and another for the lower.
If the fuse to the upper melted, my first guess would be a short to ground.
If the upper points got welded together but the fuse did not melt then for some reason its trying for maximum power for long period of time.

Illustrations snipped from a scanned '69 Dodge Service Manual.
upload_2019-7-7_8-35-4.png


upload_2019-7-7_8-37-28.png
 
Last edited:
Using this drawing from a 1966 booklet.
When the system voltage is low (relative to the set point), not much current flows through the coil.
The spring holds the upper contacts together.
Current flows directly through the regulator to the alternator's rotor.
The only resistance in the circuit is the rotor windings. This limits the current flow to 2 or 3 amps. (specs vary with specific alternator).
upload_2019-7-7_8-47-53.png


If there is a short to ground, then there is no resistance and current flow will increase greatly.
upload_2019-7-7_8-59-49.png


Then the fusible link melts and there's no flow.
upload_2019-7-7_9-7-56.png



Those illustrations are from this booklet.
Link is to page 5 which addresses the fusible wires but the whole beginning should be useful.
Alternators and Regulators (Session 228) from the Master Technician's Service Conference
 
A bit of an update here, going to be a bit longer so bare with me.

So I installed the new VR and the car charges again. I noticed on the ammeter that when pressing on the accelerator when the engine is idling the ammeter pegs all the way to the charging side for about 0.5s then returns to normal value. When I was cruising down the road the ammeter was stable a bit under the halfway mark on the ammeter, but it also pegged the same way when for example accelerating from an intersection.
So I decided to get rid of bad connections at the bulkhead with the MAD conversion and installed an volt gauge instead. Now I have an overcharging problem, at first the needle was jumping between 14-16 volts at higher engine speeds and at idle it's dead solid at 12. I cleaned all connectors and grounds that I could think of and insulated the soldered splices in the MAD conversion even more and that ended the fluctuating and gave me stable 15v of charging. Again idle is fine at a bit over 12v.
Now I'm out of ideas what to try, grounds from battery to engine block, block to firewall are cleaned and showing a ohm reading of 0,3. The VR is properly grounded, bulkhead is clean and the VR sees about the correct voltage, have a drop under 0,5v there. Installed also an new wire from the bulkhead to the VR.
The thing that I'm wondering about is that the VR sees the overcharging, but don't seem to do "anything". I can measure 15,5v from the key side but it doesn't seem to regulate it.

Any ideas what to do next?
 
Old Mopar alternators don't charge much, or any at all at idle speeds. Even more if parts are changed overtime, wiring is getting old and maybe a larger pulley is mounted on the alternator, limiting it's charging rpm even more.
If originality is something you care about, you could decide to upgrade to a dual field alternator and regulator. They look similar to the older ones and they work a little better than the single field alternators.

If you just want to fix it quickly, get a '90s Nippondenso alternator out of a Mitsubishi or something like that.
They have a built-in regulator and only have 2, maybe 3 wires, and will charge at idle and provide a steady 14v charge at all times.
 
There's only a couple reasons I can think of why the ammeter was showing high battery charging.
1. The battery is very low on charge and/or in poor condition.
2. The regulator is not working correctly and voltage is rising with rpm. This creates an overcharging situation and will ruin the battery (or worse).
 
I am running a dual field alternator, the VR is a mechanical original style one I just never even thought about installing the electrical one as this should work as good. I really don't care for if it looks original or not, this car won't be an concours restoration anyways, I just want it to run properly. These problems actually started to occur when I switched from a single to dual field alternator.

@Mattax the battery is new, bought it in may. And should be of good quality, it's a Bosch.
I was thinking if the VR could be adjusted, I saw in the links provided that can bee done. Or should I just leave it alone?
 
It still should not jump voltage like that. Frankly for the "root" of this problem I'd suspect a partially shorted alternator field. Get yourself a shop manual, there's a procedure in there to measure field current draw.

And, I would not waste time re-engineering mechanical regulators. Most any aftermarket regulator you buy nowadays is going to be electronic in a mechanical case, so to speak.

You may have a loose / poor ground between VR and battery.
 
Dual field alternators require regulators with 2 field wires.
Unless you put one field to ground on the alternator, in which case you can use old style regulator, But you still have a single field alternator.
 
BigBlockMopar said:
But you still have a single field alternator.
Click to expand...
Not really.
What you have the exact same alternator with positive controlling regulation instead of ground controlling regulation.
In the US its called 'A' Circuit vs. 'B' circuit. In the UK to quote BC_Johnny on Speedtalk "I know it as 'field to positive' and 'field to negative' switching, whether the reg is interposed between the positive feed or negative ground." That's a lot clearer description.
 
Dodge6719 said:
I was thinking if the VR could be adjusted, I saw in the links provided that can bee done. Or should I just leave it alone?
Click to expand...
Yes they can be adjusted.
There was one type that had an adjustment screw, but most required some gentle bending. Yes follow the shop manual.
But voltage should not be jumpy. The regulator should be reacting quicker than you would see on a meter - certainlty an analog meter.
The battery could be new, but low on stored energy. Recharge it slowly and if need be take it for a load test, or do crude one yourself. Then recharge it before starting the car.
20 to 30 amps of recharging for a 1/2 second after starting, OK. But then it should steadily drift toward 0 amps (centered). That should take a minute or longer.
The engine after starting should be on fast idle, so the alternator can easily supply that much power for recharging.
Once you are driving around it should not need much more charging. Often a little bit of recharging is needed after being stopped at light, especially with lights and wipers on. Just a few amps - not more than 5.
 
@67Dart273 This is actually the Standard motor products VR101 that is of the traditional mechanical type, it could be adjusted but I don't either think its the problem as I have blown 3 already.
I did the first test of the field current draw test where it says to measure voltage drop between battery and VR field terminal. This should not be more than 0,55v, I have 1,01v. Now then it says to go through the connections on the route to the battery and find where it changes significantly, that was the IGN terminal on the VR where it is 0,6v drop. If i i unplug the IGN terminal from the VR and measure directly from the IGN connector I have 0,1-0,2v drop. The voltage is almost correct if the VR is unplugged, is this normal?
 
Dodge6719 said:
@67Dart273 This is actually the Standard motor products VR101 that is of the traditional mechanical type, it could be adjusted but I don't either think its the problem as I have blown 3 already.
I did the first test of the field current draw test where it says to measure voltage drop between battery and VR field terminal. This should not be more than 0,55v, I have 1,01v. Now then it says to go through the connections on the route to the battery and find where it changes significantly, that was the IGN terminal on the VR where it is 0,6v drop. If i i unplug the IGN terminal from the VR and measure directly from the IGN connector I have 0,1-0,2v drop. The voltage is almost correct if the VR is unplugged, is this normal?
Click to expand...

I'm talking about actual current draw. The field is simply a wound magnet, and if something causes a couple of turns to be shorted, this could relegate the field magnet to a few percent or a lot of percent "lesser" of it's original performance, and worse, the shorted turns increase the DC current draw. Seems to me somewhere between 4 and 6A max.

ONLY OTHER thought I have on blowing up VRs is maybe a short / intermittent short somewhere, either the green field wire or something wrong in the alternator brushes/ field, and that very well could be. At the price of a VR might be helpful to try another alternator...........and this coming from a guy who doesn't like to "throw parts" at a problem.
 
BigBlockMopar said:
Dual field alternators require regulators with 2 field wires.
Unless you put one field to ground on the alternator, in which case you can use old style regulator, But you still have a single field alternator.
Click to expand...

I wish you guys would stop calling these "dual field". They are ISOLATED field meaning "not grounded"

The current path for grounded field (up through 69) is battery neg..........ground path...........grounded brush.........through the field........to the VR field terminal..........and back to battery

The current path for isolated field is from battery NEG.........to VR ground.........through the green wire to one field terminal...........through the field..........and through the blue wire back to battery

They both work pretty much exactly the same. The VR modulates current through the field magnet to control output
 
Dodge6719 said:
If i i unplug the IGN terminal from the VR and measure directly from the IGN connector I have 0,1-0,2v drop. The voltage is almost correct if the VR is unplugged, is this normal?
Click to expand...
No current flowing so there is no drop in voltage.

Lets look at a circuit with a few branches.
upload_2019-8-5_14-53-3.png

If the battery positive is at 12 Volts above ground, what is the voltage at the switches?

If that is difficult. Imagine the battery is a pressured air tank at 12 Pa, and the switches are valves preventing the pressurized air from escaping. What is the pressure at the valves?

Like pressure, voltage only drops when electrical flow experiences resistance. You disconnect the only branch of the circuit where current was flowing, and you get a situation like above.

Close two of the switches and what happens?
upload_2019-8-5_15-3-16.png

The electromagnet sees 11 Volts and the lamps see 10.6 Volts.
The voltage dropped as current tried to flow through the poor connections.
Similar to pressure drops when pushing water or air through a pipe that is too small.
 
Mattax said:
No current flowing so there is no drop in voltage.
Click to expand...

Yes of course, I know this. I'm sorry, I was tired and not thinking straight.

Going to make a temporary field wire to see if it changes anything and measure the voltage drop on all connections to the VR next.
 
66jim said:
I would first make sure you have a solid ground on the regulator and clean the connections to regulator and alternator use dielectric grease, then I would suspect China.
Click to expand...
I hear that some of the issues with the regulators is that when they are making them they are painting both the inside and outside of the case. This means that no matter how well you gound the case the circuit board is not grounded. China strikes again.
 
You must log in or register to reply here.
-

Back
Top