Help with Volt Gauge flicker.

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Lil Scamp

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We just installed an aftermarket instrument cluster and gauges on my dad's 71 duster. I advised him to also re-route the alternator wire bypassing the bulkhead connector as he now has a volt gauge instead of the amp gauge so we did. The car has always had a bad light flicker and you can really notice it now with the new volt gauge bouncing from 14v-16v. After lots of searching I see its not uncommon when a MSD 6AL is installed (which has been on there since the car was built). I found a thread on another forum which was successful after a diode was installed from the ignition wire from the MSD box. I tore apart an old radio and found a diode and spliced it inline with the wire, no change. The weird thing is, if you take the ignition wire feeding the voltage regulator off and hook it directly to the battery, the flickering stops and it charges perfect. Has anybody had this problem and had success fixing it?

Here is the successful thread: Ammeter/Main Voltage Fluctuating | Moparts Question and Answer | Moparts Forums
 
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First, what are we working on?

Next, what do you have for an alternator / regulator, IE Mopar, Delco, etc?

"Generally" the thing you just described is caused by VOLTAGE DROP in the harness, and involves a connection / contact making poor contact. "One" scenario would be a poor contact in the ignition switch. There's some dirt / corrosion/ whatever, and the sensing/ power lead that goes to the VR "senses" low voltage because of the poor connection. The VR tells the alternator "ramp it up." The voltage rises, the connection sort of "makes" better, and suddenly it's TOO much. The voltage drops off.

This does not ALWAYS happen this way. Every once in awhile, it's caused by a "loopback" condition in the harness or ground. It can also in rare instances be the VR itself.

The fact that you jumpered to the battery, and it "fixed" the problem, indicates you are on the right track. ONE WAY to work around this is to use the key to trigger a relay, and then power ignition loads and the VR / and field off the relay. you want to fuse the relay contacts, come off the starter relay stud. You can put the relay either under the dash or under the hood.
 
That was my next step, I just thought there might be a simpler and cleaner solution. Whenever I google something like "MSD voltage flicker" it seems common that people run into the problem after they install a MSD ignition system. I doubt he has ever changed the ignition switch so it might be worth a try.
 
Actually there WAS a guy on one of the other forums who experienced interaction between the MSD and VR. I'd forgotten. Try paying attention to wire routing. The MSD and other high power ignition can actually trigger itself and cause "it's own" misfires. Likewise, the spark energy can radiate interference into other circuits. You want the plug wires routed away from the trigger wiring and other sensitive circuits. You want stuff like the VR wiring "dressed" close to a ground plane, IE the firewall and engine. Make certain the engine and firewall are well grounded to each other.
 
I am dealing with the same issue right now! Actually, I have been working on it since last October! I did the MAD bypass and my head lights started strobing. I was stumped.



I am going to rewire my MSD 6AL-2 tonight to be temporarily powered by a separate battery (not powered by my car) and see if it makes any difference. From there i am going to start rerouting the wiring to see if I am getting interference. I have gone over EVERYTHING since last October and can't find any corrosion of poor connections. I was starting to suspect the MSD box but... now I am fairly certain after googling the issue. I will post an update tonight.
 
Weak440 said:
I am dealing with the same issue ................
I have gone over EVERYTHING since last October and can't find any corrosion of poor connections..
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Might be the ignition switch itself. Adding a relay is one way around it.
 
Thanks for the help! My replacement JUST shipped from RockAuto about 20 minutes ago. I can't wait to get this fixed and start driving it again!
 
Weak440 said:
I am dealing with the same issue right now! Actually, I have been working on it since last October! I did the MAD bypass and my head lights started strobing. I was stumped.



I am going to rewire my MSD 6AL-2 tonight to be temporarily powered by a separate battery (not powered by my car) and see if it makes any difference. From there i am going to start rerouting the wiring to see if I am getting interference. I have gone over EVERYTHING since last October and can't find any corrosion of poor connections. I was starting to suspect the MSD box but... now I am fairly certain after googling the issue. I will post an update tonight.
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This is exactly what his duster is doing. After 67dart mentioned low voltage comming from the ignition switch, i remembered seeing only 11-ish volts at the new meter and was thinking it was just inaccuracy of the new gauge so im thinking it actually has a voltage drop.
 
We finally resolved the issue. It seems to be more of an issue of the small ignition wire and its length cant get the voltage change to the regulator fast enough. We added a 10 gauge wire all the way over by the regulator and used a relay to power the regulator. No more flicker.
image.jpeg
 
Very good. Even though I have a fair understanding of "how it works" and "how to fix" you certainly did a nice neat job of wiring
 
I have been slowly and methodically tracking down any voltage drop I can find. I have had the best luck when replaced the crimp on connections in the bulk head for the blue wire from the altenator and when I replaced the ignition switch.

This is the best it has been in a very very long time.



Does that seem normal? I have never had a volt meter on a car the entire time it is running.
 
It should be better (more stable) than that. What do you have for a regulator? "And just what is" the voltage drop?
 
Weak440 said:
I have been slowly and methodically tracking down any voltage drop I can find. I have had the best luck when replaced the crimp on connections in the bulk head for the blue wire from the altenator and when I replaced the ignition switch.

This is the best it has been in a very very long time.



Does that seem normal? I have never had a volt meter on a car the entire time it is running.
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I dont know if a voltage drop is what you need to be looking for. I believe its more a problem of the voltage regulator not "seeing" the voltage change fast enough because of old under sized wire. by the time the regulator sees the voltage is at 14 volts, its actually higher causing it to have a slow reaction.
 
Having exactly the same problem on my 69 Dart - voltage on the Autometer volt meter wanders between 13.8 and 16+ volts a lot. The stock ammeter is still hooked up and there's no MSD box , it's all stock.
 
swinger1969 said:
Having exactly the same problem on my 69 Dart - voltage on the Autometer volt meter wanders between 13.8 and 16+ volts a lot. The stock ammeter is still hooked up and there's no MSD box , it's all stock.
Click to expand...


If you still have an original type mechanical regulator, that can be one cause. 'How to tell' Look UNDER the VR. If the case appears, OEM, look for two large wirewound resistors. That is mechanical. The electronic ones have a pretty much flat bottom, at least, no resistors

This one is mechanical

440-1621-large.jpg


This one has electronic guts in an old style case.........no resistors

s-l300.jpg
 
If you have truly "run down" anything else you can think of, and I'm not one to advocate "throwing parts" you might try a new VR
 
Lil Scamp said:
We just installed an aftermarket instrument cluster and gauges on my dad's 71 duster. I advised him to also re-route the alternator wire bypassing the bulkhead connector as he now has a volt gauge instead of the amp gauge so we did. The car has always had a bad light flicker and you can really notice it now with the new volt gauge bouncing from 14v-16v. After lots of searching I see its not uncommon when a MSD 6AL is installed (which has been on there since the car was built). I found a thread on another forum which was successful after a diode was installed from the ignition wire from the MSD box. I tore apart an old radio and found a diode and spliced it inline with the wire, no change. The weird thing is, if you take the ignition wire feeding the voltage regulator off and hook it directly to the battery, the flickering stops and it charges perfect. Has anybody had this problem and had success fixing it?

Here is the successful thread: Ammeter/Main Voltage Fluctuating | Moparts Question and Answer | Moparts Forums
Click to expand...

I am new to the forum but wanted to share my experience related to the OP's original post ... I have an '67 Barracuda that I converted from a slant 6 to 360 crate motor. I originally installed a chrysler orange box ignition kit and electronic voltage regulator with a stock replacement 3 wire alternator and wired into the original harness with a ballast resistor. I used it for almost 8 yrs with no charging problems with the ammeter bypassed and a new voltage gage wired into the harness. This spring I decided to start taking the car to the track and wanted to put an MSD iginition on to give me some versatility and rev control. Removed the orange box and ballast and wired up the new MSD Digital 6. Voltage gage now bounced around and lights flickered at a steady rate not related to engine rpm. I pulled my hair out for hours ... changed the MSD power wiring, went thru all my grounds, checked voltage drop thru the harness, new VR, new alternator ... everything I could think of and nothing changed it. Thanks to this thread and Lil Scamp's note about how it went away connecting the VR right to the battery, I decided to wire my VR right to the starter solenoid battery post ... And, viola, the problem went away.

I am fairly proficient at electrical wiring and have wired lots of stuff but this one has me stumped. I would love to hear some theories on why this happens ... my best guess is the MSD causing some kind of feedback or surging thru the harness itself and thus the VR senses this surging and acts appropriately. What's puzzling is the harness is fed off the same starter solenoid post that is now feeding the VR.

In any case, hope this post can help the next person that has this problem and save them hours and money!
 
chillent said:
.. my best guess is the MSD causing some kind of feedback or surging thru the harness
Click to expand...

This is MOST probably exactly what happened. Even MSD, on their own site, warns against stuff like false triggering. That is, the MSD produces so much spark energy, that improper wiring "dress" can cause the MSD to "trigger itself."

This is not of course isolated to MSD. In this day and age of microprocessors, magnetic triggers and other sensitive circuits, fairly common.

You need to keep trigger (such as distributor) leads short, dressed close to the vehicle body (ground plane) and twist the pickup wires.

If you are old enough, you remember TV twinlead? You used to twist that to resisto noise pickup. In today's world, ethernet (Cat5 and other) cables do the same thing......tight twists in the pairs to reduce signal cross over.
 
I have the same problem.... since I installed a MSD RTR Distributor... so how did you connect the VR to the Start relais ? My VR has two wires coming into... a blue and a green one..both are comming from the alternator... so do I have to connect the blue Or the green cable ( FLD on the alternator ) to the start relais... and where do I need to hook up the cable ? The start relais has a couple of connections...
I thank you very much in advance for your help

Greetings Juergen
 
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