Flickering or pulstating Headlights

[Mattax]

Thanks for the link I read through your write-up, still not understanding fully what all the internal parts do so I'm gonna read my 1970 Plymouth FSM about it

Sounds like a plan.
One thing that is really helpful to understanding the parts, is the relation between electricity and magnetism.
Basically, if a wire is formed into a circle and electricty passed through it, a magnetic field is created.

Wrap it enough times and the magnetism is strong enough to move things.

It works the other way too.
If a magnetic field is spun passed coils of wire, electricity will flow in the wire as long as the two ends are connected to something, like a light bulb.

The wire windings in the rotor create an magnetic field when electricity flows through it. Spinning that magnetic field induces electricity to flow in the surrounding wires that don't move. The faster the rotor is spun the more electricity can be induced in those static wires. That's how the alternator can use just a little current (no more than 3 amps) to create a lot more.

Sometimes its helpful to look at the earlier system because its wiring is simpler.
When voltage drops, electricity is permitted to flow through directly the regulator.
When voltage starts to get too high, no electricity flows through.

When electic current is allowed through the regulator it goes to the positive field terminal, then through the carbon brush that rubs against the spinning copper ring.
That ring is soldered to one end of the windings.
The other ring is soldered to the other end.

I doubt the alternator is in that bad of shape it's only a few years old but it is a reman'd unit from O'Reillys.

Probably not, but if a diode can fail, a stator winding can have broken connection, and the output terminal could have been not snugged up, etc. In Feb I returned AC Delco GM type alternator because the output terminal wasn't snugged up - nor could it be. One new but junk part was all it took for that alternator to 'go bad' in less than 500 miles.

voltage is not steady at idle, it never has been... only when it's revved above 1300-1500ish RPM does it start to charge steadily (but the voltage still fluctuates). This is with the headlights off too.

Hard to draw a conclusion with a bad battery connected. See what happens with the new battery. Without a ammeter, cant say for sure whether the battery is charging or not.

This battery is toast btw I went yesterday to start the car and had to crank it a bunch to fill the carb back up after taking it apart, I couldn't have cranked it more than 15 seconds total before I heard the starter (which is a modern mini-starter even) slowing down and the voltage went well below 12 on the gauge which was too low for my Mallory ignition box to energize and fire up. Annoying!

hate to say, but going below 12 Volts during start is not that unusual. IIRC one of the shop manuals I have mentions using voltage during start as a crude test. Above 11 would be OK. Now if the Mallory needs I can't speak to.

 

[Mattax]

I've mentioned ripple a couple of times.
Basically its the left over alternating current waves when the electicity was converted to DC.
If we had an oscilliscope we could see the voltage over time.

Its usually very small compared to the voltage, so we don't see it on the meters. Something like 0.1 Volt

If a diode is bad, then that portion is not rectified and then it looks like we're seeing a bad ripple.

 

[MopaR&D]

Sounds like a plan.
One thing that is really helpful to understanding the parts, is the relation between electricity and magnetism.
Basically, if a wire is formed into a circle and electricty passed through it, a magnetic field is created.
View attachment 1715319180
Wrap it enough times and the magnetism is strong enough to move things.

It works the other way too.
If a magnetic field is spun passed coils of wire, electricity will flow in the wire as long as the two ends are connected to something, like a light bulb.

The wire windings in the rotor create an magnetic field when electricity flows through it. Spinning that magnetic field induces electricity to flow in the surrounding wires that don't move. The faster the rotor is spun the more electricity can be induced in those static wires. That's how the alternator can use just a little current (no more than 3 amps) to create a lot more.

Sometimes its helpful to look at the earlier system because its wiring is simpler.
When voltage drops, electricity is permitted to flow through directly the regulator.
When voltage starts to get too high, no electricity flows through.
View attachment 1715319209
When electic current is allowed through the regulator it goes to the positive field terminal, then through the carbon brush that rubs against the spinning copper ring.
That ring is soldered to one end of the windings.
The other ring is soldered to the other end.



Probably not, but if a diode can fail, a stator winding can have broken connection, and the output terminal could have been not snugged up, etc. In Feb I returned AC Delco GM type alternator because the output terminal wasn't snugged up - nor could it be. One new but junk part was all it took for that alternator to 'go bad' in less than 500 miles.

Hard to draw a conclusion with a bad battery connected. See what happens with the new battery. Without a ammeter, cant say for sure whether the battery is charging or not.

hate to say, but going below 12 Volts during start is not that unusual. IIRC one of the shop manuals I have mentions using voltage during start as a crude test. Above 11 would be OK. Now if the Mallory needs I can't speak to.

The Mallory box needs a minimum of 11.something volts to turn on, less than that = no spark. Today I got my new battery and it's a beast, unfortunately it did nothing for my flickering lights/voltmeter issue. I also scraped the paint off the firewall where the voltage regulator mounts and it made no difference. Here's a video of the gauge, you can hear me rev up the engine but the gauge still wobbles; the lights flicker in sync with the gauge. The video was from before I put in the new battery and cleaned the VR ground but it still acts exactly the same now...



I'll try testing the alternator tomorrow, if it is bad I'll just take it back to O'Reillys and exchange it. If THAT one goes bad, well then it might be time to "remanufacture" it myself, or just swap in a Denso.

 

[Mattax]

Redfish and 67dart273 may have something more to suggest.
What I see is not only some flickering, but high voltage. 14.5 to almost 16 V.
For ref it would be useful to know what alternator, what regulator, and how you rewired the alternator and battery feeds to the main splice.

Now that you have a new battery I think the next steps are:
a) Start the engine and measure the voltage
1. as close as you can to the regulator 'sensing' terminal.*
2. at the alternator output.
3. between the two because its easier to see the difference when measured directly.

b) Put an electric load on the system and repeat measurements. (For a load, turn the headlights and/or heater fan.)

*The easist places to measure the voltage the regulator is sensing will probably be at the alternator and at the ballast resistor.
Schematically a 70 alternator circuit is wired like this:

(insulation colors and terminal positions are representative and vary from year and model)

Voltage measured at any of these points to ground should be the same.
Voltage measured between any of these points should be close to zero.

 

[MopaR&D]

Alright I checked most of the charging circuit and didn't come up with anything. BUT then I checked voltage from the blue wire right at the VR to the battery pos terminal with the key in the Run position and got, are you ready? .... 1.5 Volts! Looks like I need either a new ignition switch or just to do the relay mod.

I probably burned up my last battery running that high of a charging voltage, it didn't seem to last as long as it should have and I just attributed it to being in an old car with old electrical parts. Which I guess was true but it turned out to be something I could/should have fixed lol.

 

[MopaR&D]

Success!! I went and bought a relay from the parts store and wired it up, didn't work at first because for some dumb reason I connected to the starter stud instead of the battery stud. Now I have a hair over 14V when charging and it's steady, no more wobbling gauge or flickering lights! Yayy!

 

[Mattax]

I checked voltage from the blue wire right at the VR to the battery pos terminal with the key in the Run position and got, are you ready? .... 1.5 Volts!

Let me make sure I understand:
Removed the triangular plug connector at the regulator.
Turned the key to Run. engine off, and measured a voltage drop from battery positive post to the connector.

Is that right?

Also Where is the Mallory connected to power ?

 

[Mattax]

Success!! I went and bought a relay from the parts store and wired it up, didn't work at first because for some dumb reason I connected to the starter stud instead of the battery stud. Now I have a hair over 14V when charging and it's steady, no more wobbling gauge or flickering lights! Yayy!

That's good.
But still want to figure out where the bad connection is since power for other stuff may be flowing through it.

 

[MopaR&D]

Let me make sure I understand:
Removed the triangular plug connector at the regulator.
Turned the key to Run. engine off, and measured a voltage drop from battery positive post to the connector.

Is that right?

Also Where is the Mallory connected to power ?

Well it seems to be all fixed now but... no I left the connector plugged into the regulator and measured straight into the blue wire (punctured it with my pointy multimeter leads) and got 1.5 volts with the key turned to Run position with the engine off.

The Mallory box has power leads going straight to the battery terminals and gets an Ignition On signal from the blue wire that used to go to the coil positive on the old factory points setup.

 

[Mattax]

That's good.
But still want to figure out where the bad connection is since power for other stuff may be flowing through it.

I should have written bad connection or short. That's why I asked what I did in the previous post.

 

[MopaR&D]

I should have written bad connection or short. That's why I asked what I did in the previous post.

Sorry we're posting really quick check post #59. I thought the bad connection would be in the ignition switch itself?

 

[Mattax]

Sorry we're posting really quick check post #59. I thought the bad connection/short would be in the ignition switch itself?

Well that's what I'm not sure about.
Normally there's very little current flow with the key in run.
Trying to figure out where the current was flowing. Then we can figure where the drop may have occured.
When you removed the ammeter, did you tie the two wires together behind the dash?

Well it seems to be all fixed now but... no I left the connector plugged into the regulator and measured straight into the blue wire (punctured it with my pointy multimeter leads) and got 1.5 volts with the key turned to Run position with the engine off.

Got it.

The Mallory box has power leads going straight to the battery terminals and gets an Ignition On signal from the blue wire that used to go to the coil positive on the old factory points setup.

OK.

 

[superchargeddrt]

Success!! I went and bought a relay from the parts store and wired it up, didn't work at first because for some dumb reason I connected to the starter stud instead of the battery stud. Now I have a hair over 14V when charging and it's steady, no more wobbling gauge or flickering lights! Yayy!

There you go, glad you got it fixed. I find that a lot of times it's the ignition switch contacts. Glad you got it fixed!

 

[Mattax]

Depend on what you checked. From that one test, the problem could have been anywhere in the flow path before regulator wire.
The current flow path is battery to field, and battery to ignition trigger. Together they probably don't draw more than 3 amps.
If there was no voltage drop between battery positive and F+ or J, then the regulator wire is the most likely suspect. Could be either a short or a bad connection.

If there was the same 1.5 volt drop at F+ and J, then the problem could be at the bulkhead connections, the igntion switch, its connector, or the wires between them.

1.5 Volts is a big drop for a circuit flowing 2 or 3 amps. If you had the lights and fan on, and you saw 1.5 Volts I would not have been so surprised.
That should be your next test. Do a voltage drop check for resistance in the flow path for the lights, fan and wipers. If there is a problem, do the lights seperately to figure out if it is in the switch or not. Power for the lights doesn't go through the ignition switch.

 

[Mattax]

OK. If that mades sense. Then lets illustrate the flow path in relation to voltage.
Orange dashes represent current flowing. Arrows indicate direction by common convention. (ie Current flows from higher voltage to lower voltage).
Engine OFF, Key in RUN.

If there are no shorts, just a few amps are flowing.
If all connections and wires are in perfect condition voltage at the bulkheads, Alternator B stud, Resistor J, Alternator F+ will also be 12.5 Volts.
Voltage on the other side of the resistor will be less the 12.5 Volts. Voltage at F- may be close to zero.

Since you measured a 1.5 Volt drop at the regulator, connections or wire along that path has resistance.
There was also a voltage drop when the engine was running.
Not sure what the voltages were at the VR and alternator, but the instrument panel meter is probably connected downstream of the fusebox run/accessory side.
If so, then the flow path that overlaps in both situations is key Run connection to the regulator sense terminal.

But there could be more than one poor connection or wire. Therefore check for voltage drops under load.
Here's another example. Its wiring is the same as previous example (doesn't show you've installed a relay for the ignition and field.)

Engine Running. Lights On, Heater Fan on Low, battery recharged.

If all the connections and wires are good, voltage at alternator B stud, the bulkheads, and the battery positive terminal will be the same.
Illustrated above is:
1 amp to the Mallory CD box
9 amps to the headlights
5 amps to the instrument and parking lights
3 amps shown going to the heater fan (low speed)
2 amps to alternator field, 1/2 amp or less to Mallory on switch.

 

[MopaR&D]

OK. If that mades sense. Then lets illustrate the flow path in relation to voltage.
Orange dashes represent current flowing. Arrows indicate direction by common convention. (ie Current flows from higher voltage to lower voltage).
Engine OFF, Key in RUN.
View attachment 1715324487
If there are no shorts, just a few amps are flowing.
If all connections and wires are in perfect condition voltage at the bulkheads, Alternator B stud, Resistor J, Alternator F+ will also be 12.5 Volts.
Voltage on the other side of the resistor will be less the 12.5 Volts. Voltage at F- may be close to zero.

Since you measured a 1.5 Volt drop at the regulator, connections or wire along that path has resistance.
There was also a voltage drop when the engine was running.
Not sure what the voltages were at the VR and alternator, but the instrument panel meter is probably connected downstream of the fusebox run/accessory side.
If so, then the flow path that overlaps in both situations is key Run connection to the regulator sense terminal.

But there could be more than one poor connection or wire. Therefore check for voltage drops under load.
Here's another example. Its wiring is the same as previous example (doesn't show you've installed a relay for the ignition and field.)

Engine Running. Lights On, Heater Fan on Low, battery recharged.
View attachment 1715324492
If all the connections and wires are good, voltage at alternator B stud, the bulkheads, and the battery positive terminal will be the same.
Illustrated above is:
1 amp to the Mallory CD box
9 amps to the headlights
5 amps to the instrument and parking lights
3 amps shown going to the heater fan (low speed)
2 amps to alternator field, 1/2 amp or less to Mallory on switch.

Thank you for the images that really helps me understand what's going on. I'll test the voltages at the places you mentioned when I have some free time over the next couple days and report back.

 

[MopaR&D]

I think I've narrowed it down to the bulkhead connector. I'm going to clean things up as best I can and put some dielectric grease in there see if it makes a difference. Everything under the hood checked out OK but both sides of the ballast resistor gave around 10.8V instead of 12.3-ish like everywhere else. I have a wideband O2 sensor BTW which turns on with the key and I can see the voltage across the battery drop as the sensor heats up, I finally figured out lol.

The ballast resistor doesn't really have any current going through it anymore with the way I've done the wiring btw, I could have taken it out but got lazy

 

[Mattax]

If there is no current to speak of through the ignition wire, then the resistance could be in the bulkhead feed or the igntion switch or connectors.
Think of it like the water pipes in your house. When there is no flow, the pressure is the same everywhere. It doesn't matter if the line to the 2nd floor bathroom is plugged up with mineral deposits. Only when the shower is running does the constriction cause the pressure to drop.

 

[MopaR&D]

If there is no current to speak of through the ignition wire, then the resistance could be in the bulkhead feed or the igntion switch or connectors.
Think of it like the water pipes in your house. When there is no flow, the pressure is the same everywhere. It doesn't matter if the line to the 2nd floor bathroom is plugged up with mineral deposits. Only when the shower is running does the constriction cause the pressure to drop.

I "cleaned" and lubed the bulkhead connector and rechecked, same voltage. I wouldn't be surprised if the ignition switch is on its way out it's never been touched in the 11 years I've had the car and I doubt it was replaced before I got it.

 

[Mattax]

Lets just walk through a couple of voltage drop scenarios.
First one is fairly obvious. If current is flowing from the battery, a poor connection at the battery positive terminal will result in less voltage at every point downstream.

Next is the same system, but with two bad connections.
One bad connection on the alternator output wire at the bulkhead.
The other bad connection on the ignition switch feed at the connector.
Notice the alternator stud and the battery are at the same voltage.
The voltage drop is after the resistance to the current.
So everything after the ignition switch connector might read 11 Volts with the 2 amps going through.

Turning on the heater fan would increase the flow though the switch and voltage will drop more.
But turning on the headlights would not change the situation.
J would stay at 11 Volts (assuming the battery voltage stayed at 12.5 Volts).

Notice in all of these tests the alternator output wire is just an extension of the test probe.
To check the condition of that circuit, we will need to repeat the tests with the alternator running.

These are just examples. Also your circuits are different. Sketch out what you've done and then you can come up with tests to narrow the areas to look in. Sometimes its just as easy to take connectors off and do visual checks first.

 

[Mattax]

I "cleaned" and lubed the bulkhead connector and rechecked, same voltage. I wouldn't be surprised if the ignition switch is on its way out it's never been touched in the 11 years I've had the car and I doubt it was replaced before I got it.

Did you see this?
Ignition Switch Connector Fail
Didn't say what year but its a keyswitch in the column year.

 

[coalman]

Welcome to the light/voltage flickering club!!!

 

[MopaR&D]

It's been pretty dang solid the past few times I drove the car since doing the regulator relay mod, even at idle. Lights still dim a bit but no more flickering. I'll have to dive deep into my wiring to find the bad connection as I did the ammeter bypass slightly different than the "MAD" method I just forget how exactly. I also want to move the ON signal for my wideband O2 sensor so it doesn't turn on with the key in Accessory position, I'm afraid I'm gonna burn it up.

 

[superchargeddrt]

It's been pretty dang solid the past few times I drove the car since doing the regulator relay mod, even at idle. Lights still dim a bit but no more flickering. I'll have to dive deep into my wiring to find the bad connection as I did the ammeter bypass slightly different than the "MAD" method I just forget how exactly. I also want to move the ON signal for my wideband O2 sensor so it doesn't turn on with the key in Accessory position, I'm afraid I'm gonna burn it up.

The relay mod works just about every time. If you put the adjustable regulator in then you could adjust the voltage up a bit making your lights brighter at idle. I have mine set at 14.5 volts when driving.

 

[coalman]

I am going to get back into this one, lights still flicker, with all the mods. I have my instrument cluster out to look at my headlight switch and wiring. Some of the wires have some little humps in them with no discoloration. Does this mean they have bad continuity or they are getting warm? Thanks a bunch.