Low voltage readings from VHF and GPS, radio acting up

[Birdman84]

Recently bought a Sea Hunt 186 and first few outings I was getting low voltage readings (9.5-11v) on the GPS when motor wasn't running (everything running off 1 battery at the motor) and VHF low voltage alarm. I decided to separate the motor and electronics so I re-wired the electronics inside the center console and purchased a new starting battery for the motor as it was a few years old. Bought another brand new deep cycle for the electronics, charged it up and first time out, within first few minutes my VHF was already beeping with low voltage, GPS readings would fluctuate from around 10.5v to 12.0v, randomly every few seconds. The radio I just installed progressively gets quieter as well, like it isn't getting enough power. Pulled the battery yesterday and tested with multi-meter got 12.3 volts so I am now trickle charging it back to full so I can run some more tests, but not sure where to start. Even with the voltage warnings my electronics will last 8+ hours during outings so they can't be accurate readings. Oh and when I re-wired the electronics I put all new connectors on to ensure good connections...all is tight. Has anyone experienced something like this?

 

[GA_Boater]

Electronics use an internal reference and it is often different than the real voltage. Use a meter to measure voltage feeds to the accessories, not just the battery voltage.

Clean all the ground connections from the battery to the accessories. Just like trailers, poor grounds cause the majority of electrical issues. Do the same for the power feeds to the GPS, etc. All connections should bright, shiny and clean enough to eat off of.

 

[Birdman84]

Thanks GA_Boater, just finished re-charging the battery and it reads a full charge with the volt meter. Will hook it back up this afternoon and check voltages at both the gps and VHF with my meter to see if there are any anomalies. The negative and positive connections to the battery have all new connectors so I am pretty sure that isn't the problem. Unless I have some other sort of issue with my grounding which I am wondering if that could be the case...

 

[NYBo]

Are the circuits for these devices routed through a fuse block? Check the fuses and sockets for corrosion.

 

[GA_Boater]

Are the circuits for these devices routed through a fuse block? Check the fuses and sockets for corrosion.

Yes - this too.

One thing you can do is get a hank of wire and connect it directly from the battery to the GPS or one of the accessory power leads and another hank directly to the battery negative - Eliminate the boat wiring temporarily.

See what the device voltage displays and if it's about the same as the battery voltage, the problem is the wiring between the battery and the dash busses, either power or ground. Disconnect the temporary wires one at a time to see which side, power or ground, has the problem.

 

[Birdman84]

Thanks guys, sorry for the late reply...busy weekend. After getting a better look this weekend I found both the GPS and VHF go through a fuse block which I checked thoroughly. I did find some of them had a little corrosion, cleaned all fuses and sockets and re-seated but it made no difference. I checked voltage at the GPS and it was reading same as voltage at battery (12.55v) but the display shows 11.9v. The VHF doesn't display voltage but I am reading 12.55v at this unit as well. It still beeps low battery though. Both units are within 2 years old. The stereo issue I think I resolved which is wired to an accessory switch not the fuse block. I found a loose ground and fixed it...no more issues there. I didn't run a wire straight from battery to the devices only for the fact that I was getting consistent readings at both ends the way it is wired now. I am considering replacing the fuse block entirely to see if that makes any difference since they are inexpensive. Maybe it would be better to just buy a digital battery gauge and forget about it?

 

[dingbat]

There are two components to electricity, voltage and amperage.

You’ve proven nothing more than you have 12.55 volts at each units. You need to check the amperage which is the test Ga_boater was having you run

BTW: analog meters have far fewer issues measuring voltages

 

[Birdman84]

There are two components to electricity, voltage and amperage.

You’ve proven nothing more than you have 12.55 volts at each units. You need to check the amperage which is the test Ga_boater was having you run

BTW: analog meters have far fewer issues measuring voltages

Ok so if I understand correctly, even though I am getting same voltage readings at each end, there could be an issue with resistance somewhere affecting the amperage, or current, of the power to these units? I will run GA_boaters test on the GPS next chance I get, unfortunately the weather doesn't permit it today. If I see a difference in what the display reads then I will try to narrow down the cause between the battery and devices. I have a suspicion if there is such a problem it'll be between the battery and fuse block, considering both devices connected to the block are acting up. Will post findings soon..

 

[dingbat]

Ok so if I understand correctly, even though I am getting same voltage readings at each end, there could be an issue with resistance somewhere affecting the amperage, or current, of the power to these units? I will run GA_boaters test on the GPS next chance I get, unfortunately the weather doesn't permit it today. If I see a difference in what the display reads then I will try to narrow down the cause between the battery and devices. I have a suspicion if there is such a problem it'll be between the battery and fuse block, considering both devices connected to the block are acting up. Will post findings soon..

Don’t count the displayed voltage on the GPS as gospel. The voltage displayed may or may not be the input voltage to the unit. Not uncommon for units to display the voltage from the unit’s internal 12 volt power regulator/supply

 

[Birdman84]

That's what's I don't get, when I tested the input voltage to the unit by placing my meter leads on the power plug connecting to the Garmin, it read the same as what I got at the battery terminals. It's just far off from what the unit displays (unit shows .6v less, sometimes up to 1.5v less). I can't see what the VHF is processing but it is getting the same as the battery at its plug as well. Something is telling these devices that they are not getting sufficient power, but I have yet to have any performance issues with them. My VHF will go off no matter the conditions or whether I'm using it or not. My original thought was that if the amperage or current to these devices was problematic (i.e. wrong size wire, corroded connections, etc) that it would show a voltage loss at the devices, but that turned out not to be the case, it is the same voltage reading on both ends of the circuit (tested with a Fluke true rms multi-meter).

 

[dingbat]

That's what's I don't get, when I tested the input voltage to the unit by placing my meter leads on the power plug connecting to the Garmin, it read the same as what I got at the battery terminals.

There is is no current component to removing the connector from the back of the unit. You’re simply measuring the battery voltage from a remote location

You need to measure voltage with the unit drawing current thru the wires.

Think of a garden hose. Doesn’t matter where you install a pressure gauge you get supply pressure. But open the spray nozzle the pressure drops relative to the flow....

 

[mike_i]

what make and model vhf and gps do you have? do both units work when turned on all day? my vhf would generate false low voltage alarms too but would work fine. I found there is a system setup option in my vhf which allowed the user to set a low voltage alarm threshold which was default to something around 13v, I don't remember the exact number. I change it to something like 10 or 10.5 volts, don't remember the number. The manufactor states the radio will work to low voltage of 9 or 10 volts, don't remember the exact number, that's why I changed the alarm threshold to 10 or 10.5v. as others have posted the voltage readings that the units display are close to but not the real input voltages.

PS are both units on separate fuses? and are you measuring the voltages at the plug of each unit using both 12v and ground wire in the plug and not cliping the neg meter lead to ground then measuring both 12v leads?

 

[Birdman84]

There is is no current component to removing the connector from the back of the unit. You’re simply measuring the battery voltage from a remote location

You need to measure voltage with the unit drawing current thru the wires.

Think of a garden hose. Doesn’t matter where you install a pressure gauge you get supply pressure. But open the spray nozzle the pressure drops relative to the flow....

That makes a lot of sense, hopefully this afternoon I can find some time to play with it some more.

The VHF is a standard horizon gx1300 and the gps is a Garmin 74sv both purchased in the last few years. That's a good point about the vhf, I read that in another thread and forgot to check the settings. I will check that out too and post what it is set to. The 2 devices are on separate fuses. When measuring the voltage at the plug I put the leads on the 12v and neg contacts inside the plug.

 

[Birdman84]

OK so I found the problem. Thank you GA_Boater for suggesting the straight run from the GPS to the battery. I don't know why I didn't do this to begin with as it's 101 stuff but doing so showed me a much closer reading to actual from the battery. I then tried to figure out where the problem was between the battery and fuse block. After checking everything I couldn't find an obvious sign of a problem and was minutes from purchasing a new fuse block to see what that would do. Last ditch effort was to replace all fuses in the block since I had a bunch of extra laying around and sure enough that fixed the problem. The original 5A blade fuse looked fine minus slight graying on the contacts, didn't expect that would cause such issues but sure enough it did. I am now getting the same reading from a straight hook up to the battery as I am by going through the block..thanks to everyone for your help!

Also I did check the setting in the Horizon VHF and did not find a setting to turn off/change the alarm for low voltage. Maybe my unit doesn't have this option, but nevertheless, after 15 mins of it being on I did not have it go off once with a new fuse in. Hope this helps someone in the future

 

[GA_Boater]

The straight run was to eliminate the wiring and stuff between the battery and the device. In this case it worked. :thumb:

Wanna save some future angst? Put some non-conductive electrical grease on the fuse contacts. It blocks the humidity/salt in the air and slows down the oxidation (gray stuff) on the contacts or use gold plated fuse blocks/fuses. Go with the grease! Check your auto parts store for a product like this, they often have small packages for sparkplug wire boots;

 

[Birdman84]

The straight run was to eliminate the wiring and stuff between the battery and the device. In this case it worked. :thumb:

Wanna save some future angst? Put some non-conductive electrical grease on the fuse contacts. It blocks the humidity/salt in the air and slows down the oxidation (gray stuff) on the contacts or use gold plated fuse blocks/fuses. Go with the grease! Check your auto parts store for a product like this, they often have small packages for sparkplug wire boots;

No kidding, got a tube of that in my tool box. Will grease them next chance I get, thanks for the extra tip!!

Happy Boating