Lost 12V Ground 1 circuit Interior Lights, Ideas on finding

[Kamphiker]

While Changing out Vent fan Motor in Lavatory I lost power to the circuit. This also includes 5 other Overhead Lights on same circuit.

Fuse is not blown (I have a PD4645 Converter/ charger).

In running test with my Multimeter, IF I attach a temporary ground (Length of wire/alligator clips) to the Negative side of the wire intended for the vent fan to the PD4645 case (Only because this is the only close ground source I can find, I show proper voltage (12.6 Plus depending on PD4645 charge Mode).

Second Test I ran was measure voltage through the ground side of bad circuit I get 12 Volts measured on the ground side...... Isn't this an Indication of a shorted ground ?

When I attach the Temporary ground the 5 lights work as they should (I don't know about the New Vent Fan Motor as I have not tried to put back in operation).

For the life of Me I can't find the location of fault in either the Lights (I have pulled them out of the ceiling and the appear to have no shorted wires etc) OR the wiring I can access behind the fixtures.

I Have a PDF of my RV electrical schematics from Winnebago for my Motor home (WF324V) and I'm having problems finding the connectors on the wiring harness as they don't seem to be in indicated locations.

One question is do I simply need to re-establish a good ground on this 1 circuit without finding the Break ?

is there a easier way of finding the proper ground wire other than probing all the Ground wires (I know they are the WHITE colored wires) ?

Accessing the wiring within the ceiling not possible as is the wires for the circuit that I believe run from the ceiling down the interior wall. The bundle of wires appear to run under the bed which I have to remove to access. the wire bundle at this point appears to be 20 or more individual wires.

Open to words of wisdom

Getting ready for vacation next week and this is kicking my butt.

Thanks in advance

[Kamphiker]

Found the grounding problem / location.

Ring terminal that attaches to grounding plate on the MH Frame rail was not attached. Not only this one, but there are 12 ground wires with ring terminals that connect to same 3/8" Bolt. 9 out of the 12 basically fell off as i was checking them. Corrosion is the culprit.

Really a blessing in that by the number of miles I'll be putting on the vibrations etc from the roads would have caused the others to have failed.

Now tomorrow I have to find some either at Lowes / HD or Grainger.

[steved28]

Kamphiker wrote:
I was able to use coat hanger wire and grab the 2 wires and pull close enough to opening to run test on the ground side and there is continuity from this point to the lights etc.

Tracing from this point to the grounding source is my next step but I'm not going to put a lot of effort as the Bundles of wires in the harness is vast & runs in 2 different directions.

Wow, if I had to guess, I might say you NEVER had a good ground from that wire. That perhaps you were always just pulling the ground from the fan mount (mounted into metal?).

[Kamphiker]

After many hours of tracing wires, I finally found how Winnebago ran the 2 wires from the 5 lights & fan (daisy chained yes). They were run down between the shower stall and the back wall of the RV.

I had to remove a small access panel for access to the plumbing under the shower pan. I was able to use coat hanger wire and grab the 2 wires and pull close enough to opening to run test on the ground side and there is continuity from this point to the lights etc.

Tracing from this point to the grounding source is my next step but I'm not going to put a lot of effort as the Bundles of wires in the harness is vast & runs in 2 different directions.

I'm opting at this point to just cut the Wire splice in new wire and run to a ground and call it a day. I'm running out of time before my trip starts and have to many other items to get done.

Thanks to everyone on giving some direction.

[myredracer]

Kamphiker wrote:

Open to words of wisdom

Getting ready for vacation next week and this is kicking my butt.

Thanks in advance

I hope you solve this soon and report back! Dying to know what the issue was. 🙂

[wnjj]

MrWizard wrote:
maybe i missed it
but i did not read where he says the NEW Fan is not working
only that LIGHTS 'down stream' from the replaced fan are not working
no blown fuses, no loose ground/NEGATIVE wire in the fuse panel

sounds like he mixed up one or two wires

I think you missed this:

OP wrote:
When I attach the Temporary ground the 5 lights work as they should (I don't know about the New Vent Fan Motor as I have not tried to put back in operation).

It’s an open ground for sure. The only mystery to him was why there was 12V on the ground wire prior to the temporary attachment. The answer is that the 12V passes right through the light bulb filament when the ground is floating.

[MrWizard]

maybe i missed it
but i did not read where he says the NEW Fan is not working
only that LIGHTS 'down stream' from the replaced fan are not working
no blown fuses, no loose ground/NEGATIVE wire in the fuse panel

sounds like he mixed up one or two wires

[shastagary]

the 12v circuits should get the ground connection starting at the converters dc power fuse panel there should be a separate ground bus for the 12v connections there then it daisy chains to each light on the circuit with a connection at each light start at the beginning ground connection at the fuse panel.

[steved28]

myredracer wrote:

steved28 wrote:


I would agree with you if this was not a Winnebago. Not sure how they did it in '06, but Winnebago does not use crimps today. They actually solder all the joints and shrink wrap them. One of the best practices in the industry IMO.

Wow, who does that! You def. can't get better than that. If that's what he has, that should narrow the cause down.

Actually I misspoke, it's a a solderless welding process, then shrinkwrap. If you advance this video to 14:35 on the clock, they show it.

Build video

[myredracer]

steved28 wrote:

myredracer wrote:
Factory crimp connections can be so poorly done, the wires slip out of the connectors by just touching them (BTDT). And the crimp tool may have been used on the plastic cover and not the metal barrel inside on a compression connector/terminal (BTDT too). And splices using marrettes my have also been done poorly. So when you work with or near something 12 volts, you can cause wires to separate. I would say the culprit connection is in the vicinity of where you were working and something you touched.

I would agree with you if this was not a Winnebago. Not sure how they did it in '06, but Winnebago does not use crimps today. They actually solder all the joints and shrink wrap them. One of the best practices in the industry IMO.

Wow, who does that! You def. can't get better than that. If that's what he has, that should narrow the cause down.

[steved28]

myredracer wrote:
Factory crimp connections can be so poorly done, the wires slip out of the connectors by just touching them (BTDT). And the crimp tool may have been used on the plastic cover and not the metal barrel inside on a compression connector/terminal (BTDT too). And splices using marrettes my have also been done poorly. So when you work with or near something 12 volts, you can cause wires to separate. I would say the culprit connection is in the vicinity of where you were working and something you touched.

I would agree with you if this was not a Winnebago. Not sure how they did it in '06, but Winnebago does not use crimps today. They actually solder all the joints and shrink wrap them. One of the best practices in the industry IMO.

[MrWizard]

Unless you pulled so hard on the wiring yo pulled something loose in the ceiling

You crossed wired it
Or a wire slipped back into the ceiling

There should be an equal number on hot wires and negative wires at you ceiling junction
Should be the same number on each side pos and neg
Start there
What do you have ?

[wa8yxm]

Id you are measuring battery voltage on the GROUND side of the device that is not woking that indicates an OPEN ground.

Suggestion Take a test light This is an ice pick like device with a light bulb in the hand and a wire lead with clip. Clip onto the GROUND wire and poke a known good ground spot with the tip.. Do this with a SINGLE LAMP turned on (not the fan though a fan might work) and if you get "Dim" (slow) operation... plus a DIM test lamp. YOU FOUND THE PROBLEM make the ground solid instead of protected (The test lamp is a protected ground. protected against a dead short)

[myredracer]

Factory crimp connections can be so poorly done, the wires slip out of the connectors by just touching them (BTDT). And the crimp tool may have been used on the plastic cover and not the metal barrel inside on a compression connector/terminal (BTDT too). And splices using marrettes my have also been done poorly. So when you work with or near something 12 volts, you can cause wires to separate. I would say the culprit connection is in the vicinity of where you were working and something you touched.

Lights, fans, etc. are wired in series from one to the next so somewhere in that circuit you've caused a connection to come apart. If you've taken the voltmeter and verified the presence of 12 volts where you are working, remove 12 volt fuses until the 12 volts you've got turns off. Then put the fuse back in and remove all others. See what 12 volt lights are still on and pull out nearest one(s) and check the connection there to see if a connection has come apart. If problem not found, try gently wiggling wires in the ceiling to see if you can tell where a wire (2 conductor) goes to a light in the bathroom and then check the connections there.

12 volt wires are simply laid on top of the bottom chords of trusses and run like sloppy spaghetti all over. Lots of slack to wiggle/tug on wires. You can also get access into the ceiling space through lights, AC grilles, skylight bezels, etc. and you can get a hand up in there to see which direction wires run.

Also, if you look at the wires, there may be a color coding stripe along them which will help identify what wire is what. There should be no need to install another ground wire. Wires will run down inside walls to get to the panel and are also run in the hollow space under cabinets. Splices can be hiding in all sorts of places.

[MrWizard]

Sounds like you crossed wired the down stream negative wires to the source feed hot positive wire

You have 2 hots running to those lights and no negative/ ground for them