Electrical Issue Today - Voltage on Ground Bar?

Hey all, had a weird issue pop up today. I recently installed a BlackVue dash camera setup with a Powercell 8 backup battery, been working pretty great and today right after starting the truck, the camera starts cycling off/on like it was detecting the ignition source being turned off. Oddly enough, when that would happen, all my other switched accessories would also go defunct - light bar, ditch lights, rear lights, etc.

All of my accessories are wired up through a BlueSea (BS) fuse box with a 100amp breaker and each accessory has it's own ground, power, and fuse there. I started troubleshooting and noted that my voltage tested was detecting a current on my ground bar in the fuse box, which appears to be shared as all the ground screws and the ground post that ties to the truck chassis were lighting up the tester. The ground on the battery and the ground bolt on the truck itself were fine.

The dash cam battery pack is wired from a 4-pin relay with a power coming off the BS fuse box, going out to the power, signal coming off an ignition powered add-a-fuse, and a ground. The power and ground coming back from the relay to the battery pack are tied in directly and from there, an accessory, power, and ground go to the camera box which powers all three cameras. I noted that when I removed the add-a-fuse and signal source from the dash cam battery, the other accessories appeared to work. I figure there's a short in the system and start pulling things out so I can look for loose wires and whatnot but didn't really find anything. After checking all fuses, wiring, and switches, I start with the dash cam battery pack and test just that through the fuse box with nothing else connected to it and sure enough, as soon as the signal gets power from the key being turned the ground was lighting up again. I decide to replace with a new relay of the same kind, since they came in a pack, and again the ground bar is showing a current but this time when I run the meter over several of the ground points, I hear a sound from the relay and the battery starts actually pulling a charge, dash camera starts up like it's working fine, and the current is gone from the ground bar.

Here's the relays I had purchased,

$19 True MODS 6 Pack 4-Pin 12V Bosch Style Fused Relay Switch Kit [Interlocking Harness Socket Holder] [14 AWG Hot Wires] [SPST] [30 Amp] 12 Volt Automotive relays with Fuse for Auto Cars

https://www.amazon.com/dp/B01NBAO1SA?ref=ppx_yo2ov_dt_b_product_details

I still have to test the other connections to make sure there's no fault in any other relays or wiring, but assuming it was that relay, what in the world would have made it go bad in just a couple of weeks besides poor build quality? And why did the replacement appear to be stuck in a similar fashion until audibly tripping on? We had a bad storm that tripped several breakers in the house from a nearby strike a few days ago but pretty low odds it would impact this one particular relay in my truck.

I would like to replace the relay with something more trustworthy at this point and open to suggestions there. Please let me know if I'm overlooking anything obvious here, and if anyone is local I'll happily buy a few beers for a second opinion.

 

TL;DR, but I suggest getting a DVM (digital volt meter). Even a cheap harbor freight.

Set DVM to VDC (volts DC). Short the test leads together and note reading. Test leads are the black and red wires that come with the meter. I don’t mean to be rude stating what may be obvious to you… I just don’t know your level of electrical knowledge.

Measure from the battery “-“ to that ground bar. If the measurement is higher that the reading above, that ground bar is not grounded well. Disconnect the battery “-“ and clean up all the ground points. Then remove the battery “+” and clean up both battery terminals until they shine, reconnect battery cables and repeat this test.

Let us know what you find.

If you have questions, fire away. Many people here willing to help. Note: I am not familiar with the BS fuse box, but the connection from BS ground to battery “-“ would be my first suspect.

 

This is great stuff, I do have a volt meter. I didn't see a reading while touching the leads together under 20v DC unless I'm misinterpreting what you mean there.

I'll throw a photo in here as well but I checked the battery and got 12.23 volts when set on 20v DC. Then checking the ground point on the chassis next to the battery, I got the same voltage on the bolt but did see a drop to around 9.5v on several of wires that connect there. I don't have the BS fuse box fully connected right now but I attached the ground, which comes off that chassis point and the battery, and got 12.22 volts on both the lug on the fuse box and the ground connectors for the accessories.

 

1. If you're seeing voltage at ground with a multimeter, that's a good sign. Your ground bar on the fuse box should read close to what you get from chassis ground.
2. A short in a circuit should cause one of your fuses to blow. This would also cause the device attached to not power on. I'm not sure why you thought you had a short if the devices were able to power on, albeit when you disconnected your cam.
3. 12v relays use a magnetic switch. When current is passed through the coil (incoming power), the magnetic field causes the switch to move, completing the circuit. If the relay you used had a bad internal switch, it will either be permanently ON or OFF because it either has physically failed or the magnetic field being generated is not strong enough to move the contact switch.

Bosch makes the best automotive 12v relays. If you're in doubt, go with Bosch. You could also try a solid state relay that doesn't use mechanical components.

 

Would a short in the wiring for one device cause an issue with all other accessories? That was the weirdest part to me, if the dash camera battery was unplugged or plugged in and "working," all the other accessories worked as well.

My light bar and ditch lights were both tapped to a high beam fuse in the engine bay and the accessory fuse under the steering wheel. This is a carry-over from when I had diodes that allowed the lights to be triggered both by switches or by my light stalk and high beams. I removed the diodes afterward but in this configuration, the lights will only function when the switches are both depressed and the high beam is tripped. When this short or whatever is going on would happen, the two in-cab switches for the lights would no longer be backlit but if I hit one or either switch, the switch would light up and it would actually trip my high beam light on the gauge cluster. It would not actually turn the high beams on but it appeared to be feeding the signal backwards.

The other accessory are rear lights which were tapped to the ignition fuse for signal and lighting the in-cab switch. When the short would occur, that switch would completely light up but wouldn't function to power the lights.

As all of these lights had both their power and ground from the BS fuse box, and my voltage probe was lighting up on the ground bar, I assumed something is shorting and sending a current back through the ground which is preventing all other accessories from functioning. My initial thought was a loose wire or connection or wiring issue in the dash camera battery I just installed, though that was straightforward even with my limited knowledge on electrical since it's just a power and ground coming through a relay and back to the battery with a signal operating the switch within the relay when it receives power from the ignition to prevent the dash camera battery from draining the truck battery when off.

Would love to go with a Bosch relay to replace these, just prefer to find one with a pigtail kit so I don't have to second-guess my wiring at that stage.

 

The 12.2 volts measured on the BS fuse box was measured to the battery + ?

The 9.5 volts on the other wires indicates a poor connection. I’d take the screw out of the ground to fender and clean all surfaces that contact each other (except for the painted inner fender surface… we don’t want that to rust). Both sides of terminals connecting to fender, and just the part of the bolt that faces the fender. I like to use green scotch bright for cleaning connections, but sand paper, emory, etc works. Then recheck where you measured the reduced voltage. If still 9.5 V you might have a bad contact elsewhere or a bad crimp on a wire end.

keep us posted! I’m off work and taking care of stuff that needs done. But checking in on short breaks.

 

Yes, measured to battery +. I'll definitely scrub the connections when I get back from work and check again.

I'll also stop by and see if I can find another 4-pin relay from advance auto just to have on hand. Once I get things cleaned up, my plan was to wire up each accessory individually to see if any issues arise with vehicle off, in accessory, and with ignition on. I read that it's also good to test with the vehicle running in case the extra load from the alternator is causing an issue on each circuit but that will be touch with the birds nest of wiring that I have everywhere currently.

 

The issues with other accessories would depend on if you have them riding on the same circuit or if each one is on its own isolated circuit. TBH, it's hard for me to help without seeing a circuit diagram of how you have your connections. I'm a visual learner. I'm sure someone with more electrical knowledge could help you. I typically run each accessory on its own circuit so I don't run into this kind of problem.

This is how I run my accessories:
Fuse tap for IGN +12v --> Trigger (pin 85 or 86) 12V SPDT relay --> pin 87 goes to Fuse box power source --> accessory power input

Depending on power draw, I have a secondary wire from that fuse box that goes to another relay for another acessory.

Current is drawn, so accessories don't "send power", but draw power. So, think of it like a tree. The trunk is your power source of power. The leaves are your accessories. If one branch is broken (short), then that accessory no longer works. However, the other accessories should still function if they're on their own branch. If you have accesories tied to the same branch, then you could experience issues because of that branch.

 

The camera cycling on and off likely indicates insufficient voltage at the camera and like others have mentioned that's often caused by a poor connection causing the voltage drop, you're seeing it with that reduced voltage you measured on some of the circuits. For example getting 9V on a 12V electronic circuit often causes an electronic device to power cycle repeatedly. A quick test would be to try and run the camera separately off something other then the BS fuse box, preferably straight to the battery just to see if it operates correctly. If it does the fuse box can't supply the needed current, I doubt its a problem with the fuse box itself but more likely it's connections. If it were me I'd disconnect the cam for now, clean up the wiring, remove the unneeded diodes and get the wiring correct for the other devices that are connected to that box and then add in the camera system. If you have low voltage originating from a connection issue it's electrical drama just waiting to happen and when it happens it probably be in the driveway.

 

Refreshing this thread, I was able to get my system working again but never found the culprit. I cleaned up all terminal ends and replaced all connections in the system.

Fast forwarding to today, haven't had any issues and fired up the truck to see that none of my accessories were working. Messed around with the voltmeter when I got home and no blown fuses that I could find, no rat chew marks, etc., but I'm picking up voltage on my grounds for several relays when measuring from the (-) on my battery and the (+) on the voltmeter to the ground terminal connections. From what I can tell, the source appears to be the fuse box by the steering wheel where I have two add-a-fuses, one to my gauge fuse that connects to three interior switches for lights and one to my accessory fuse which goes to the relay for my dash cam. Again no blown fuses and tried swapping in different ones and trying other locations in that fuse panel. Weird that it's happening for both the dash camera and the lights (so the box itself?).

If I disconnected the signal wires from the 86 pin of the relays, the voltage would drop to 0. I popped an add-a-fuse in the engine fuse box to connect to one of the relays and it read 0, leading me to think something is off with the one in the dash. I also tried disconnecting each add-a-fuse separately in case just one was the culprit but issue remained.

I'm at a bit of a loss as to what could have happened, truck drove normally today with no codes thrown.

For reference on how the relay is setup for the dash cam, I have the 30 pin to battery power (runs through blue sea box), 87 to dash cam battery, 86 to my accessory fuse so the battery will only draw when ignition is on (and can recognize when it's off for parking mode), and 85 to ground.

Appreciate any help with this!

 

I'd take your meter set to DC voltage and put one lead on the accessory ground and the other on the battery's ground post with some accessories turned on. Should be very little voltage read across those two points and what you're reading is voltage lost (consumed) between them in their wiring and connections. Ideally it will be zero but that's not typically the case. I suspect you'll see something excessive (more than a volt). If that's the case the voltage you're reading is the voltage used (lost) by the acc circuit just to get a connection to the battery, it's typically caused by high resistance between the two locations (insufficient or loose connections, corroded wiring/terminals etc... The old saying is ground is ground the world around, point being there should be very little difference (voltage measured) between those 2 points.

You can make the exact same checks on the posative side, going from the battery + post to the acc relay's output pin with the circuit turned on, again you should see very little voltage and the same causes and circuit affects typically apply.

 

I'll be tinkering with it again tonight but currently none of my accessories will work. To eliminate as many variables as I can, I was planning to get some clip leads to wire up each accessory individually to the battery terminals and testing their function, bypassing the 100amp breaker and fuse block that everything is currently connected through.

I was reading into relays last night and trying to figure out if picking up voltage on my ground (pin 85) means the relay is energized or closed. Supposedly it doesn't matter which side you feed the signal vs ground through on pins 85/86 as it just operates like a switch. Made a crappy sketch of how the dash camera battery is wired, their instructions tell you to use an add-a-fuse to power the battery but I didn't like the idea of pulling that amperage through a fuse terminal so I wanted to hardwire the battery and use an ignition switched fuse point to act as the switch so the dash cam battery will only draw when ignition is on and can recognize when the truck is parked to switch modes.

my readings were fine on the negative and positive terminals of the breaker and fuse block with vehicle off but reads voltage on the ground bars of the fuse block once energized.

 

IMO you're easteregging at this point, jumping around without a clear picture or logical plan. Power on the ground bus is a huge red flag and you'd be much better served to determine where thats coming from and fix it. Any power you read on the ground bus is power not available to the accessories. Example, if you're reading 4 volts on the acc ground bus, there's only 8 volts to run the accessories. Stuff quits working and turns on and off when given insufficient voltage. Imagine that, both are symptoms you've indicated.

 

You aren’t wrong there, I couldn’t get any accessories to power on and no switches were toggled, so there shouldn’t have been any draw to prohibit just one set of leds from working even if amps were being reduced at the block. I just tested each accessory directly from the battery and no issues. Also tested resistance and function of each relay and they’re all still good.

Leads me to believe the issue lies somewhere from the fuse block to the battery, either the block, breaker, or wiring between has an issue. I am tempted to just replace everything there with new wiring, block, and breaker and reconnect it all afterwards. May replace terminal connectors as well.

 

Floating ground.

 

May have found the culprit, 4ga wire where it connects to chassis ground from fuse block

 

My suggestion would be to redo all that accessory wiring setup, make it neat and secure and crimp everything properly. What you're going through is electrical drama that's a result of some flakey wiring practices. It's not difficult to square it away and it'll save you headaches and time down the road

 

I just redid all the connections from the fuse block to the accessories last year so that all should be good. Just finished replacing the ground wire connection pictured above and got it all back together, everything working smoothly.

@ridefreak I appreciate your help and everyone else that responded here.