Voltage Gauge wiggle w/ turn signal normal?

[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.

[aa909]

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]

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]

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]

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.

[aa909]

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”.

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!

Originally Posted by SBSerpent

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

Originally Posted by patrickt

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.

Originally Posted by jhv48

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

[patrickt]

Originally Posted by aa909

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.