AC volt gauge issue

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Haloo

Senior Member
Joined
Sep 1, 2019
Messages
107
Location
USA
Vessel Name
Mighty Fine
Vessel Make
Kingfisher 3125GFX
The original ac volt gauge that came with our new boat quit working, with the gauge showing no voltage to the boat even though a check of the voltage at the leads to the gauge showed 120 volts. The connections seemed secure.

I bought and installed a new gauge and it is showing slightly less than 100 volts. A multimeter check of an ac outlet with the new ac volt gauge installed shows 120 volts.

I’m very mechanically capable but have little knowledge of electrical systems. And idea what I should be doing next?
 
Hi Haloo,
Question: Before it died, did the old gauge show 120 volts, typically?
 
ScottC said:
Hi Haloo,
Question: Before it died, did the old gauge show 120 volts, typically?
Click to expand...

Great question. I don’t know. We bought the boat late in the summer and almost immediately had to deal with a family emergency. I didn’t know that ac gauge had quit working until we stored the boat on its trailer at a local marina. The marina informed me the gauge wasn’t working when they connected power to the boat to charge the batteries.
 
I'm not an electrical guru, but I have seen an installation exhibiting this phenomenon and it turned out that the electric hot water heater was tapping into the shore power near the entrance (i.e. before it got to the main circuit panel, where the gauge was). In a marina with very weak power to start with, the gauge showed notably different voltages depending on whether the water heater was on or off.


It's likely this is not the case for you, however, since I see you are measuring 120v at an outlet even after the new gauge
 
One other thought - you don't have anything producing a heavy magnetic field anywhere near the gauge, do you? Speaker, for example...
 
ScottC said:
I'm not an electrical guru, but I have seen an installation exhibiting this phenomenon and it turned out that the electric hot water heater was tapping into the shore power near the entrance (i.e. before it got to the main circuit panel, where the gauge was). In a marina with very weak power to start with, the gauge showed notably different voltages depending on whether the water heater was on or off.


It's likely this is not the case for you, however, since I see you are measuring 120v at an outlet even after the new gauge
Click to expand...

Interesting. I had all of the breakers except the main turned off and still got slightly less than 100 volts. However, I will check each breaker independently and see if there is any effect.
 
ScottC said:
One other thought - you don't have anything producing a heavy magnetic field anywhere near the gauge, do you? Speaker, for example...
Click to expand...

I don’t think so, but I’ll check.
 
Haloo said:
The original ac volt gauge that came with our new boat quit working, with the gauge showing no voltage to the boat even though a check of the voltage at the leads to the gauge showed 120 volts. The connections seemed secure.

I bought and installed a new gauge and it is showing slightly less than 100 volts. A multimeter check of an ac outlet with the new ac volt gauge installed shows 120 volts.

I’m very mechanically capable but have little knowledge of electrical systems. And idea what I should be doing next?
Click to expand...

What kind of multimeter are you using to measure the 120 volts? What kind of gauge is it that is indicating less than 100 on the same wires? Both should be fairly accurate for that measurement so one of them is showing a bad result obviously. A known good, calibrated multimeter as a tie breaker would be a reasonable approach to solving the issue.
 
sbman said:
What kind of multimeter are you using to measure the 120 volts? What kind of gauge is it that is indicating less than 100 on the same wires? Both should be fairly accurate for that measurement so one of them is showing a bad result obviously. A known good, calibrated multimeter as a tie breaker would be a reasonable approach to solving the issue.
Click to expand...

Done. I started with an inexpensive multimeter from our local hardware store. It showed 120 volts at the leads. But the numbers are difficult to read on this multimeter. So I ordered a much better multimeter on Amazon with a few hundred 5 star reviews. It also showed 120 volts, and is much easier to read.
 
KnotYet said:
In this case I would suspect the new gauge. Easily verified.
Click to expand...

How do I check the new gauge to see if it is defective?

I apologize if the answer is obvious to most, but electrical stuff is not my strength. I intend to improve in this area as fast as I can.
 
Haloo said:
How do I check the new gauge to see if it is defective?

I apologize if the answer is obvious to most, but electrical stuff is not my strength. I intend to improve in this area as fast as I can.
Click to expand...

With two meters showing 120V and the gauge showing less than 100V it seems the gauge is not accurate. Is it an analog/needle gauge or a digital one?
 
Just to double check, all of these measurements are being taken across the posts of the gauge vs in other parts of the system, e.g. pedestal, inlet, main breaker, etc.

If you are, with your meter, measuring 120V across the posts of the gauge and it isn't showing that, it is either broken or out of calibration. If it doesn't have a calibration screw, it is broken.

What make/model of gauge is it?
 
sbman said:
Surprises me that a new Blue Sea gauge would be faulty, but it can happen. You've verified that the AC Hot is on the + terminal?
Click to expand...

Yes, hot lead is on + terminal.
 
gkesden said:
Just to double check, all of these measurements are being taken across the posts of the gauge vs in other parts of the system, e.g. pedestal, inlet, main breaker, etc.

If you are, with your meter, measuring 120V across the posts of the gauge and it isn't showing that, it is either broken or out of calibration. If it doesn't have a calibration screw, it is broken.

What make/model of gauge is it?
Click to expand...

Yes, I am certain I took the measurements from the leads to the voltmeter. But because I’m pretty obsessive about things, I’m going to pull the panel again and recheck with both multimeters.

The gauge does have a calibration screw. The directions (see below) seem to suggest that this is used to set the needle to “0” if it is not already doing so with power off. Should I be using the calibration screw to set the gauge to the reading I’m getting on my multimeter with the power on?


4. Calibration
The voltmeter is calibrated at the factory and recalibration should never be necessary. However, if adjustment does become necessary the needle may be reset to the zero mark.
In the center of the black area on the meter front is an adjustment screw. This screw activates a small cam that deflects the meter needle slightly to adjust the needle position.
Using a small screw driver, turn the screw no more than 90 degrees right or left, as necessary. DO NOT ROTATE THE ADJUSTMENT SCREW THROUGH 360 DEGREES
 
Make sure both leads of the probe are on the gauge posts or a bad reference could make the gauge look bad.

I'm betting thevgauge is right and thebreference isn't. But, that is just because itbis a new gauge. The proof is in the measurement.

If you measure exactly as the gauge does, and utnisnt reading right, it isnt right.

If it was an older gauge, I might try calibrating it. But, if it is returnable -- that is the best idea.

If calibrating thebgauge, it can only be adjusted as much as ut can be adjusted-- keeping 0V showing as 0V. Setting it otherwise really isn't calibrating it anymore than setting a dead clock to the current time of day.

Good luck!
 
Blue Sea Systems is sending me a new voltmeter. I’m glad I chose their product and will do so in the future.

I’ll also update this thread when the new voltmeter is installed.
 
The problem was the voltmeter. I installed the replacement from Blue Sea Systems and it indicates the correct voltage.
 
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