Voltage Gauge wiggle w/ turn signal normal?

patrickt · #1 (**permalink**) 06-12-2021, 02:15 PM

"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.

aa909 · #2 (**permalink**) 06-12-2021, 02:52 PM

Quote:

Originally Posted by patrickt

"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!

patrickt · #3 (**permalink**) 06-12-2021, 02:58 PM

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.

aa909 · #4 (**permalink**) 06-12-2021, 03:30 PM

Quote:

Originally Posted by patrickt

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!

jhv48 · #5 (**permalink**) 06-13-2021, 08:50 PM

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”.

patrickt · #6 (**permalink**) 06-14-2021, 06:12 AM

Quote:

Originally Posted by jhv48

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.

jhv48 · #7 (**permalink**) 06-14-2021, 08:08 AM

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.