Flickering or pulstating Headlights

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MileHighDart

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Headlights are flickering at idle and while driving.
Not just headlights really but headlights, tail lights, dash lights.

My setup is as follows.
Newly installed 5.9 Magnum, with serpentine setup and '99 magnum alternator.
New battery
Voltage regulator appears to be solid state type.
Madd electrical ammeter bypass was done at the same time as the engine swap.

With the old 318, and before the madd bypass all I can remember is the lights would dim at idle, and brighten when raising the rpm. Don't remember them flickering, but its been a while.

I'm no electrical genius, but pulled out my volt meter and checked a couple things.
Battery with car off is reading 12.65 volts.
Battery with car running at idle is fluctuating between 14.25 and 15.25
At the alternator output stud, about the same 14.25 to 15.30
The alternator seems to make a little kind of whining noise, just for a second, every time the lights flicker.
So flickering lights and I think the charge rate is a little high, and fluctuating
Any ideas ?
 
Could be high ripple voltage. The AC current isn't being fully rectified.
 
This will fix your flickering headlights. Its caused by dirty/worn ignition switch contacts. I modified mine like this and it works perfectly.


Charging system relay modification.jpg
 
That seems like a pretty big range for the voltage to be swinging around just at idle. Is the voltage regulator new? If that’s a Denso alternator you should have plenty of juice at idle.
 
superchargeddrt said:
This will fix your flickering headlights. Its caused by dirty/worn ignition switch contacts. I modified mine like this and it works perfectly.


View attachment 1715167195
Click to expand...
Or maybe a new ignition switch would fix it? Of course the relay would probably be a lot cheaper. Does the relay fix the fluctuating voltage at the battery too?
 
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MileHighDart said:
Or maybe a new ignition switch would fix it? Of course the relay would probably be a lot cheaper. Does the relay fix the fluctuating voltage at the battery too?
Click to expand...
Yes it does. The reason the lights are flickering is because the voltage is fluctuating. The reason the voltage is fluctuating is because the voltage from the ignition switch and going to the center (I) terminal on the regulator is fluctuating due to the dirty or worn ignition switch contacts. The I terminal is how the regulator senses how much charge is needed. It drove me nuts until I came up with this fix. Trust me it will fix it and it's probably an under $10.00 fix. Let me know if I can help.
 
Also wouldn't hurt to start with a new regulator (being as you said it wasn't new). The one I mention on the diagram is adjustable so you can set the voltage to anything you want. I set mine to 14.5 volts when the engine is above idle. Makes the lights nice and bright.Also make sure you clean off the paint under the regulator mounting screws so you get a good ground. If this doesn't fix it do what I suggested and you will be good to go.
 
Where do I find an adjustable regulator? Will local parts places have it? You have a part number or anything?
 
You don't need an adjustable VR. What you need, as already said, is to get solid "no dropped" voltage to the VR.

Hook a meter one lead as close to the VR IGN terminal as you can gte and the other on battery POS. You are hoping for a very low voltage, maybe less than .3 v (3/10 of one volt) Whatever above that you read is ADDED to the VR set point, IE if you read .8V, and the VR is correctly at 14, the battery will "run" at 14.8.........example.
 
67Dart273 is right you don't need a adjustable regulator (just nice to have). If you look at the top of the diagram you will see that I got it from Ebay from a company called Roadrunner Electronics. Just make sure that your regulator is good. The modification above worked well for mine. Good Luck
 
superchargeddrt said:
67Dart273 is right you don't need a adjustable regulator (just nice to have). If you look at the top of the diagram you will see that I got it from Ebay from a company called Roadrunner Electronics. Just make sure that your regulator is good. The modification above worked well for mine. Good Luck
Click to expand...

Duh, sorry I didn’t see it, but do now, thanks
 
We’ll ordered up a regulator, new pigtails, a relay and plug w pigtails, from Advance auto, pic it up tomorrow
 
I generally don't like to see voltage over 14.5.

On my dart, I had the same problem until.......I replaced the regulator for the instruments with a solid state unit. 5V is achieved by the mechanical instrument regulator contacting 5/12'ths of the time, thus creating an uneven drop. I had done the bulkhead bypass (I didn't bypass the ammeter, I bypassed the entire bulkhead) and that certainly made things less smoky, but the flickering didn't cease until I replaced the IP regulator. My lights are more solid than the lights on my Neon, now.

Super easy to make one using a 5V solid state regulator and heat sink, or buy one like this for $.

I'd still replace the system regulator with a new solid state, no matter what.
s-l640.jpg
 
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Jos what you say is a good idea, but we are talking about the voltage regulator, not the instrument limiter/ regulator
 
We’ll, step one, I replaced the regulator making sure it’s well grounded. Cut the old connector off and soldered the new connector on. Plugged it into the new regulator and fired it up. Now at idle checking from the battery, it’s not fluctuating nearly as much but is reading steady at 15.2 !
Starting to wire up the relay right now.
 
Don't feel alone, many MANY guys came before you on the harness voltage drop issue.
 
67Dart273 said:
You don't need an adjustable VR. What you need, as already said, is to get solid "no dropped" voltage to the VR.

Hook a meter one lead as close to the VR IGN terminal as you can gte and the other on battery POS. You are hoping for a very low voltage, maybe less than .3 v (3/10 of one volt) Whatever above that you read is ADDED to the VR set point, IE if you read .8V, and the VR is correctly at 14, the battery will "run" at 14.8.........example.
Click to expand...
Ok this is getting weird. Set my multimeter to 12v poked into the blue wire that goes to the VR ign as close to the plug as possible, the other lead to pos battery terminal. Reading is 11.5
 
jos51700 said:
I generally don't like to see voltage over 14.5.

On my dart, I had the same problem until.......I replaced the regulator for the instruments with a solid state unit. 5V is achieved by the mechanical instrument regulator contacting 5/12'ths of the time, thus creating an uneven drop.

Super easy to make one using a 5V solid state regulator and heat sink, or buy one like this for $.
View attachment 1715167435
Click to expand...
Really? That fixed the pulsating headlights as well? Shouldn't have anything to do with that but if it worked fot you I say check i
MileHighDart said:
Ok this is getting weird. Set my multimeter to 12v poked into the blue wire that goes to the VR ign as close to the plug as possible, the other lead to pos battery terminal. Reading is 11.5
Click to expand...

MileHighDart said:
Ok this is getting weird. Set my multimeter to 12v poked into the blue wire that goes to the VR ign as close to the plug as possible, the other lead to pos battery terminal. Reading is 11.5
Click to expand...
That is definitely wierd. I would expect a few tenths of a volt. If you are getting that there is a ground on the blue wire. Might be something with your meter. If yo have a test light try going from the blue wire to ground and see if it lights. If it does then the blue wire is not grounded and you're getting a wierd feed back through your meter. Sorry I've been away but I spent the whole day in my garage working on the Dart
 
superchargeddrt said:
Really? That fixed the pulsating headlights as well? Shouldn't have anything to do with that but if it worked fot you I say check i



That is definitely wierd. I would expect a few tenths of a volt. If you are getting that there is a ground on the blue wire. Might be something with your meter. If yo have a test light try going from the blue wire to ground and see if it lights. If it does then the blue wire is not grounded and you're getting a wierd feed back through your meter. Sorry I've been away but I spent the whole day in my garage working on the Dart
Click to expand...

I tried the test light thing and it did not light.
 
MileHighDart said:
Ok this is getting weird. Set my multimeter to 12v poked into the blue wire that goes to the VR ign as close to the plug as possible, the other lead to pos battery terminal. Reading is 11.5
Click to expand...

You sure you had the key in "run?" Double check by connecting from the blue to ground. Should be "full" battery voltage
 
67Dart273 said:
You sure you had the key in "run?" Double check by connecting from the blue to ground. Should be "full" battery voltage
Click to expand...

Oh, no that was with the key off. Must have missed that.
I'll check with the key on and let you know.

Update:
Ok, with the key on, but car not running.
Now I get a reading of .95v
 
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That is still pretty high. That is nearly one volt and will cause your "normally set at 14v" regulator to charge at nearly 15V One way to "fix" this is to break the blue "ignition run" wire where it comes out of the bulkhead into the bay, use the bulkhead end to trigger a relay, and feed the underhood loads off the relay.

Whatever drop you read there (.9) ADDS to the normally 14V VR setting.

Part of what happens here, is the resistance in whatever terminal/ ignition switch) is causing this drop.........and it might be a combo of 2 or more, will show high resistance, cause a drop under load, the VR senses "low" and charges higher. Then the resistance "arcs across" and makes "better" and the voltage surges. This can repeat over and over.

Another cause is a "loop" such as poor grounding. I like to install a big ground jumper between engine and firewall. One way to do this is to look at your pass side front head. Those same boltholes are unused on the REAR of the left head. Take an "eye to eye" (starter) cable about a foot long, bolt to the rear of the head with a short bolt, and to the firewall, either a substantial through bolt/ nut/ star locks or maybe bolt to the master cylinder stud.

Also remove and scrape and clean around the VR mounting flange, reinstall make sure the bolts are not stripped and use star locks
 
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