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Old 06-12-2021, 08:45 AM
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Default Voltage Gauge wiggle w/ turn signal normal?

Hey guys, quick question

I've got a 2014 BDR and just had the engine rebuilt and reinstalled. Running down the check list after 100 miles to make sure everything is working properly (so far so good).

But I noticed the volt gauge needle on the dash will wiggle back and forth about 0.3 volts when the turn signal is on (FYI the needle stays pinned at 13.5-14V at idle and 14.5V when driving without the turn signal on). I never paid close attention to the Volt gauge when driving so I can't recall if this is normal or if I have a ground issue somewhere after reinstalling the engine.

Thanks in advance for your feedback!
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Old 06-12-2021, 09:22 AM
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But I noticed the volt gauge needle on the dash will wiggle back and forth about 0.3 volts when the turn signal is on (FYI the needle stays pinned at 13.5-14V at idle and 14.5V when driving without the turn signal on).
It is either: a) Perfectly Normal; or b) The voltage regulator (VR) is having trouble keeping up with the load change of the signal filaments blinking on and off. The most common reason for voltage (and current) fluctuation at idle, causing a wiggling or "wavering" needle, in these cars is a poorly grounded voltage regulator. A lot of VR mounts on our cars are on fiberglass, which is a pretty shi**y ground. Do this test: With the engine idling, put the turn signal on and watch the needle waver. Then run an alligator clipped wire from a known good ground to one of the corner bolts that holds the VR down. If that fixes it, make the ground permanent. Try that first before we explore other alternatives.
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Old 06-12-2021, 11:39 AM
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normal dont worry about it...
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Old 06-12-2021, 11:57 AM
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normal dont worry about it...
Thank you for that, Appreciate the input! I took some pics of the alternator wiring (next post) to see if this is correct
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Old 06-12-2021, 12:00 PM
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It is either: a) Perfectly Normal; or b) The voltage regulator (VR) is having trouble keeping up with the load change of the signal filaments blinking on and off. The most common reason for voltage (and current) fluctuation at idle, causing a wiggling or "wavering" needle, in these cars is a poorly grounded voltage regulator. A lot of VR mounts on our cars are on fiberglass, which is a pretty shi**y ground. Do this test: With the engine idling, put the turn signal on and watch the needle waver. Then run an alligator clipped wire from a known good ground to one of the corner bolts that holds the VR down. If that fixes it, make the ground permanent. Try that first before we explore other alternatives.
Patrick thanks for the quick reply. Here are some pics of the wiring on my alternator:





First pic shows the ground from the engine to the chassis. The alternator has 2 red wires, one I can trace back to the solenoid on the starter, the second is hidden under wiring mesh but I don't think it's the ground. Is it possible the ground is wired in there?

Am I missing something?

thanks again for everyone help!
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Old 06-12-2021, 12:31 PM
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Alternators usually have a ground connection, labeled as such, on the back just like BATT, FLD, or STAT. But not always. And they usually take their ground from their bracket bolt to the side of the block. Snap a pic of the manufacturer's label on the Alternator. You know, like Delco-Remy Model #12345, etc.

And you can't really tell just by looking at a ground whether it's any good or not, or whether you need another one somewhere else. You have to measure the current and do voltage drop tests, which all are very easy to do once you learn how. FWIW, I have more than one ground and continued adding grounds until the current that was passing through each ground cable was down to an amperage level that I liked to see. On the other hand, the car ran fine, and the lights and fans worked fine taking their ground connection off the frame, with only a single 10 gauge ground wire from the head to the firewall/frame. But on the third hand, my amp gauge needle started wavering after a good 10+ years of never doing that. It was cured by adding an additional ground wire to the voltage regulator case to supplement the little ground wire that was in the harness.
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Old 06-12-2021, 01:02 PM
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Alternators usually have a ground connection, labeled as such, on the back just like BATT, FLD, or STAT. But not always. And they usually take their ground from their bracket bolt to the side of the block. Snap a pic of the manufacturer's label on the Alternator. You know, like Delco-Remy Model #12345, etc.

And you can't really tell just by looking at a ground whether it's any good or not, or whether you need another one somewhere else. You have to measure the current and do voltage drop tests, which all are very easy to do once you learn how. FWIW, I have more than one ground and continued adding grounds until the current that was passing through each ground cable was down to an amperage level that I liked to see. On the other hand, the car ran fine, and the lights and fans worked fine taking their ground connection off the frame, with only a single 10 gauge ground wire from the head to the firewall/frame. But on the third hand, my amp gauge needle started wavering after a good 10+ years of never doing that. It was cured by adding an additional ground wire to the voltage regulator case to supplement the little ground wire that was in the harness.
Hey Patrick

I googled the part # on the back at it's a Powermaster. here's the wiring diagram online



Looks like the small wire is just the "idiot light" on the dash if battery stops charging. The larger red wire goes to the solenoid or battery and I'm clearly missing the ground wire.

So what gauge ground wire should I get, 10 gauge? and can I piggy back it on the same ground on the chassis shown in the post above (the one that goes from the engine to the chassis)?

Interesting that this diagram shows the "ground as optional"
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Last edited by aa909; 06-12-2021 at 01:14 PM..
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Old 06-12-2021, 01:06 PM
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What's 300 millivolts between friends?
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Old 06-12-2021, 01:15 PM
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"One Wire" alternators like yours do not have external voltage regulators, so you don't have to look for one. I see on the instruction a little bolt hole for a ground strap but I don't see that connected on yours. But that doesn't necessarily mean your alternator isn't sufficiently grounded. To answer that question, put your Volt/Ohm meter on the lowest voltage setting. Then start the car and turn on all the lights, fans, and anything else you have to create electric load. Have someone rev the engine to 2500 RPM and put one lead of your VOM on the negative terminal of the battery and the other lead on the outside case of your alternator. If you read more than .2 volts (or -.2 volts if the leads are reversed) then you need to run a supplementary ground to your alternator.
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Old 06-12-2021, 01:52 PM
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"One Wire" alternators like yours do not have external voltage regulators, so you don't have to look for one. I see on the instruction a little bolt hole for a ground strap but I don't see that connected on yours. But that doesn't necessarily mean your alternator isn't sufficiently grounded. To answer that question, put your Volt/Ohm meter on the lowest voltage setting. Then start the car and turn on all the lights, fans, and anything else you have to create electric load. Have someone rev the engine to 2500 RPM and put one lead of your VOM on the negative terminal of the battery and the other lead on the outside case of your alternator. If you read more than .2 volts (or -.2 volts if the leads are reversed) then you need to run a supplementary ground to your alternator.
Thanks Patrick, you've been tremendously helpful. However my battery is in the trunk, is there another spot I can use to check the Voltage drop?

In any case I'll have to wait till later (when I have a helper) to run this test, but I assume from what I've shared here I can drive the car in the current state without risking any "damage" to the electric system?

Thank you!
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Old 06-12-2021, 01:58 PM
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Just run a long wire, a lamp cord cut up and spliced together will do nicely, but run it to the negative terminal of the battery. There are short cuts, but they often mislead you. If you really do need a supplementary ground at the alternator, then your VOM might read a half volt or even one volt. One volt would be a lot. But by all means drive your car. At this point you are only optimizing; you're not fixing anything that's really broken. FWIW, when I run a VOM from the alternator case to the negative terminal of my battery I read .05 volts.
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Old 06-12-2021, 02:30 PM
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Just run a long wire, a lamp cord cut up and spliced together will do nicely, but run it to the negative terminal of the battery. There are short cuts, but they often mislead you. If you really do need a supplementary ground at the alternator, then your VOM might read a half volt or even one volt. One volt would be a lot. But by all means drive your car. At this point you are only optimizing; you're not fixing anything that's really broken. FWIW, when I run a VOM from the alternator case to the negative terminal of my battery I read .05 volts.
Perfect, I’ll go ahead and run the wire as you noted. Thanks again!
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Old 06-13-2021, 07:50 PM
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One wire alternators are grounded to the engine block by the mounting bolts that hold it in place to the engine block. No additional grounding wires are needed. Your alternator is correctly installed and wired as is. Hence the name “one
Wire alternator”.
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Old 06-13-2021, 10:00 PM
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Off topic. Out of curiosity, what is your ground clearance with that oil pan?
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Old 06-14-2021, 05:12 AM
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One wire alternators are grounded to the engine block by the mounting bolts that hold it in place to the engine block. No additional grounding wires are needed. Your alternator is correctly installed and wired as is. Hence the name “one Wire alternator”.
Sometimes mounting bolt brackets are powder coated, sometimes brackets are painted, sometimes the fasteners at the block or water pump are slathered up with RTV, sometimes there's a plastic washer between the fasteners, sometimes there's a rubber insulator.... The only way you can tell if a ground is really good or not is to measure it under load. Or, you can take a shortcut and just eyeball it and say "yeah, that looks like a pretty good ground to me." But you have to measure it under load. Just like measuring the resistance of a filament in a light bulb -- you have to do it when the bulb is lit, otherwise they all read 0 ohms.
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Old 06-14-2021, 07:08 AM
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A fluctuation of only about .3 volts is perfectly normal when the turn signals are flashing. What you’re seeing is the temporary loading and unloading of your electrical system. Load increases when the lights are on. Load decreases when the lights blink off. Your voltage regulator adjusts the output to the battery with each blink. You can do the same thing by manually flipping your headlights on and off rapidly or tapping your brake pedal.
Nothing to worry about here.
If your alternator wasn’t properly grounded, it wouldn’t charge your battery properly and your volt gauge would not show the 14.5 volts that you’re showing.
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Old 06-14-2021, 08:11 AM
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Originally Posted by jhv48 View Post
One wire alternators are grounded to the engine block by the mounting bolts that hold it in place to the engine block. No additional grounding wires are needed. Your alternator is correctly installed and wired as is. Hence the name “one
Wire alternator”.
Yes thank you! that seems to be the case. One good thing that came out of this exercise is I noticed we had the dash lights wired to the wrong terminal on the alternator LOL!

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Off topic. Out of curiosity, what is your ground clearance with that oil pan?
Not much, only about 3.5", and that's a low profile oil pan

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Sometimes mounting bolt brackets are powder coated, sometimes brackets are painted, sometimes the fasteners at the block or water pump are slathered up with RTV, sometimes there's a plastic washer between the fasteners, sometimes there's a rubber insulator.... The only way you can tell if a ground is really good or not is to measure it under load. Or, you can take a shortcut and just eyeball it and say "yeah, that looks like a pretty good ground to me." But you have to measure it under load. Just like measuring the resistance of a filament in a light bulb -- you have to do it when the bulb is lit, otherwise they all read 0 ohms.
Thanks again Patrick. I ran the test and it averaged about .07-.1V from the neg terminal to the alternator.

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A fluctuation of only about .3 volts is perfectly normal when the turn signals are flashing. What you’re seeing is the temporary loading and unloading of your electrical system. Load increases when the lights are on. Load decreases when the lights blink off. Your voltage regulator adjusts the output to the battery with each blink. You can do the same thing by manually flipping your headlights on and off rapidly or tapping your brake pedal.
Nothing to worry about here.
If your alternator wasn’t properly grounded, it wouldn’t charge your battery properly and your volt gauge would not show the 14.5 volts that you’re showing.
Yup, you're spot on. Troubleshooting these cars is a PITA but at least this one was a nonissue
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Old 06-14-2021, 08:16 AM
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Thanks again Patrick. I ran the test and it averaged about .07-.1V from the neg terminal to the alternator.
That's a good number. Now that you've learned how to test your grounds with a voltage drop test you can use that on other ground points on your engine/frame or dash ground connections. You do it the same way, just remember to always do it with a load on the system and have one VOM probe on the negative terminal of the battery. It's as easy as that.
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