head lights pulse after bypassing my bulkhead

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Weak440

Weak440

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So my Brother was working on his '70 Cuda and told me he bypassed his bulkhead by running a 10ga wire with a fusible link from the threaded stud on his alternator to his starter relay. He claimed that it made a huge improvement in his car overall.

I had heard of this bypass before and figured it sounded easy enough. I was in between projects the other night and figured I would give this a try in my '74 Duster.

I ran a piece of 10 ga wire with a fusible link from the alternator to my starter relay. I fired it up and this is where I feel like an idiot. At idle it us fine but at 2500 and higher the headlights pulse. At 3500 they flash even faster.

I shut it off and checked to see if I had any lose connections or had lost a ground. I couldn't find anything that jumped out at me.

I was being pressed for time so, I swapped the voltage regulator and restarted it. It made no change.

By now I was out of time and couldn't mess with it any more. I disconnected the battery and had to walk away from it.

I am hoping to get back to it this weekend. I feel like an idiot and am missing/doing something stupid. Anyone have any clues?

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Electronic or contact style regulator?

Old contact style I'd bet.
 
74 should be electronic

You might have somehow created a "loop" that is causing an oscillation

Start by wiggling the #### out of the VR connector several times to scrub the terminals clean

Clean the firewall and mounting ears on the VR and remount tight with star lock washers

CHECK for voltage drop both the ground and harness sections

To do this, Hook one probe of your meter to the "I" buss, IE switched ignition. One place you can access it is the blue field wire on the alternator. If you still have a ballast resistor, the "key" side of it

Hook the remaining probe to battery POSitive.

With the meter set on low DC volts, and the key in "run" but engine stopped, you are hoping for a very low reading, less than .3V. That's 3 tenths of one volt. You want to measure this with everything hooked up "normal."

========================

Ground side. Make this test with battery running at fast idle, warm, and battery "normalized." Check first with all accessories off, again with lights, heater, etc, on

Stab one probe right into the top of the NEGative battery stud. Stab the other into the mounting flange of the VR. Be sure to stab through any chrome, paint, rust. Again you are hoping for a low reading, not over .2V and zero volts would be perfect

If you google stuff like "ground loops" this might be what you've set up here, if it's not a "drop" problem. You can have a situation where you start an oscillation. These can be difficult to diagnose. One example of this is feedback in a PA system.
You are on a podium, with a PA. The mike picks up some noise, the amplifier makes it loud, and the speaker reproduces the noise......louder. The mike picks this noise up louder this time right from the speaker, and "sends it around again." Because of the time constants of the circuitry in the system, this turns into a howl

Because the time constant of the alternator / VR circuits is very slow, you have a pulsing.
 
It is electronic

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A bad diode or two in the alternator can result in flicker that varies with RPM.

An alternator has three phases that generate sine waves that are 120 degrees apart. Six diodes are used to flip negative portions, and conduct the positive sections to make a slightly pulsating supply. The pulsating ripple is filtered by the battery. The regulator controls the field to regulate the alternator output. A loss of a diode results in dips, missing gaps in generation of voltage. The regulator tries to adjust, seeing the dip, it increases the voltage, but because of delay, it increases as the dip passes. The voltage then peaks too high, and repeats ... resulting in flicker that varies with RPM.

The system is now more tightly coupled, by reducing the resistance. Resistance helped filter the ripple. The bypass made apparent, the diode problem.

The main cause of diode failure is a short on the alternator terminal with engine running, or jumping and starting another car with the engine running.

With all that said, a poor ground at the regulator can also result in flicker that varies with vibration.
 
It would be easy enough to disconnect this added wire at either end to see if it created the flicker problem. Faulty connections in the blue and green wires from regulator to alternator are suspect. Have a look at the white engine harness connector near back of right valve cover.
 
I'm just throwing this out there, I'm no electrical guru by any stretch!

But it seems as though this is half of the ammeter bypass, would this be problematic IF the rest of the bypass wasn't done???
 
Hey Kit, I thought about the diode idea, but this does not seem likely to be individual pulses. The alternator is spinning faster than the engine by 2x or 3x and if this shows up at only high RPM, the pulsing would be at a rate of close to 100 pulses per second with 2500 rpm form the engine; the headlights would not respond to that rate of pulsing (nor would our eyes!).

I would suggest to the OP to:
1) Try a different VR is he has one ===> OK already done.
2) Turn off and on things like radios and the blower to see what effect this has
3) Look for any filter capacitors in the car's wiring; on the back of the alternator is a good spot to look.
4) Try disconnecting the original alternator output wire and have just the new wire from the alternator output to the battery; I don't see where you disconnected the original wire...??

Also, questions to the OP:
- Is this flicker fast, like many time per second, or slow like 1 or more seconds per flash? That might help us figure this out.
- How old is the alternator?
- How old is the battery? (It may not be a good 'ballast' any more if it is old.)
 
I developed this issue recently too. I could hear the alternator field kicking on and off while the lights flickered. I figgered the regulator was bad so I installed a new one. Hmmmm, same condition. I then installed an old regulator I had in storage and still had the same problem. I ran a jumper wire to make sure the alternator and the rest of the car were all grounded the same and still had the problem. Then I ran a jumper from the battery positive to the 12 volt input to the regulator and everything was just fine--nice steady 14 volts. I found a 0.5V drop between the battery voltage and the voltage at the regulator input wire. All the wiggling of the bulkhead connector wouldn't clear it up so I put a relay in and all is well. The wire for the regulator and the wire for the ignition are the same one and I also installed a relay for the HEI. As long as I don't get any more resistance in that wire it appears all will be OK----but it's time to fix that voltage drop to avoid any other issues.
 
60jerry said:
................... Then I ran a jumper from the battery positive to the 12 volt input to the regulator and everything was just fine--nice steady 14 volts. I found a 0.5V drop between the battery voltage and the voltage at the regulator input wire. All the wiggling of the bulkhead connector wouldn't clear it up so I put a relay in and all is well. .
Click to expand...

VERY GOOD!!!!


No, bad diodes won't cause this. I actually PURPOSELY ran with only 3 diodes "back in the day"

My alternator had quit, I tore it apart and don't remember, I think one phase was screwed up. I vaguely remember I had one that vibrated the insulation off, LOL

So I was broke "till the end of the month" and ran without one phase of the alternator. You could NOT LOL listen to the radio!!!!! There was little else (at the time) that was electronic. This was in the 69RR, around 1970
 
I beg to differ about the diodes. I discovered about 35 years ago on a well abused 66 Dart Dart convertible I purchased. I changed the bad diodes, flicker went away. It did have a mechanical regulator, electronic may be some better. I used a scope to trouble shoot, then removed one lead from each diode and checked with meter. Back at that time small parts for alternators were easily purchased.
 
Interesting, Kit; maybe in your case, it was more at lower low RPM's like at a low idle (500-600 RPM)? The flicker rate would be visible. (The OP's issue was at high engine speeds.)

Well, very intersting info from 60jerry above; hope that is the issue for the OP! Perhaps the higher resistance in the VR feed creates a time delay in the circuit when it tries to change the field current; the field inductance would be part of time delay.
 
Now that we know the fix.

The IGN feed to the regulator provides both sense voltage, and the feed to the field. A poor connection results in instability. If the IGN is lower than desired, the field is energized, that current creates additional drop. The regulator is a hysteretic controller, some call it bang-bang, or ON-OFF. The added resistance increases the hysteresis, that is the voltage dead band, for regulation, resulting in flicker.
 
Thanks for all the replies! I am going to start tackeling this project this evening.

I am using an Optima red top that is probably about 7 years old. But, I haven't had any problems with it yet so... I am going to keep an eye on it. I may swap it out in the course of working on things to see what difference it makes.

The head lights pulse at about the same rate as the "hazzards" or the turn signal (blinker).

Thanks again! I will let you know what I find out and get some pics up!
 
Dang...iv been fighting this same flicker for a couple years now..but after reading this thread,i doubt I can follow it..but I think im gonna try...lol..tx..j
 
I had same symptoms. after trying a couple of new alternators and regs I decided to do the wire harness.i found some wires melted together on the interior side of the bulkhead connector.not in it but close to it
 
My car did this until I replaced the Voltage Regulator on the Instrument Module with an electronic unit (Mine was an oldschool conversion that I built from Mopar Action several years back, ymmv).
Several alternators, firewall VR's, and bulkhead bypass didn't fix it. The cluster regulator did.
 
jos51700 said:
My car did this until I replaced the Voltage Regulator on the Instrument Module with an electronic unit (Mine was an oldschool conversion that I built from Mopar Action several years back, ymmv).
Several alternators, firewall VR's, and bulkhead bypass didn't fix it. The cluster regulator did.
Click to expand...

You did something else. That is, you wiggled a connection, at the ignition switch, ammeter, bulkhead, whatever. The cluster regulator is not what made this happen
 
I had a similar problem, all lights were pulsing, changed VR and Alt, cleaned the grounds, took VR mount off remounted with star washers, still pulsed, I just put a Barracuda dash in the car, so I went through all that wiring, the bulk head was cleaned up well before reinstalling, found nothing wrong, took alt in to get checked, nothing wrong with it, they told me it sounded like a bad ground or a bulb!! Grounds were already checked by then so started looking at bulbs, one bulb in the grille had one of the locater tits broke off on the base, replaced it, problem solved. Never heard of that happening before. Don"t know if that's your problem, worth a look.
 
I know this is a old thread but, I have been battling this issue ever since I made the first post about it here. A LONG time ago. I wanted to post an update about it because, last night... I fixed it!!!

After changing voltage regulators, altenators, starter relays, cleaning grounds, adding grounds, changing the headlight switch, dimmer switch, instrument cluster voltage regulator, and much more, pretty much everything I could think of... I finally pulled the wiring harness out of the engine bay and did a complete amp meter bypass following the Mad Electronics instructions.

I put the wiring back in last night and fired it up... The lights still strobes. Exactly as before. I was about to pull my hair out.

As I was about to list the darn thing for sale it dawned on me... One last thing I had not considered. I have 3 autometer gauges. The gauges are wired in to "keyed on" power but, the back lights for them are not. They are wired in to come on when the headlights/driving lights do.

So, I unplugged the gauges from their "keyed on" power and it made no difference. I plugged them back in and unplugged the lights from the headlight circuit and the strobbing went away! Gone. I plugged them back in and it came back. So, I removed the bulbs from the sockets one at a time and when all 3 were removed... It went away.

Since I am going to be adding a volt meter to this collection... I have to ask... How do you guys wire the lights in to multiple gauges so they come when you turn your headlights on? Because, I clearly did it wrong.
 
Weak440 said:
I know this is a old thread but, I have been battling this issue ever since I made the first post about it here. A LONG time ago. I wanted to post an update about it because, last night... I fixed it!!!
Click to expand...

nicolas-cage-fells-good-con-air-head-space-1409843288n.gif
 
I have to hand it to you for your persistence! That has to be about the strangest thing I have heard of. The gauge lights should be so miniscule in power draw compared to the lights themselves that it seems illogical for them to effect the regulation..... Wiring them to the headlight output would be the logical thing to do. Are these LED or older incandescent bulbs?

How are these gauges grounded? How hard would it be to disconnect the headlights and connect these gauge lights to see what happens?
 
Apparently, at some point I put some LED bulbs in them but, I kind of don't remember it. I think remember soldering the wiring harness for the lights but, I have it all ziptied together under the dash. I must have a bad or loose ground. I will get some pics up this week of what I had and what I replace it with.
 
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