My Head light, license plate and reverse light are not working

huanvanho

I have 2017 T@B 320. The electrical from my Towing vehicle check out with 7 pin TESTER and they are tested OK. However my T@B license plate, headlight and reverse light on the T@B are not working. I changed out all the light bulbs but still not working. I checked fuses inside the T@B and nothing blown. Can someone suggest me where to look next? I need all the lights to work before the next trip. Thanks

Dutch061

The exterior lighting on the TAB will not have any fuses in the fuse block, they are fused from the TV. You said you checked the TV with a 7 pin tester and it was fine. For multiple lights that don't work that are on different circuits (IE tail lights VS. brake lights) the thing they would have in common is the ground circuit. I am not sure if these (TAB) use an "isolated ground" meaning each light has a dedicated ground wire or if they use a "common ground" meaning each light has a wire that is connected to the frame and use the frame for ground.

If it were me, I would start at where the harness comes into the TAB from the 7 pin connector to see if the ground wire is connected to the frame or not. If so, make sure it is clean and tight. Lightly tug on the wire to make sure it isn't broken where the terminal is attached. If it is broken, it will stretch.

Brad

falcon1970

I assume you meant the headlights and reverse lights on the tow vehicle are not working.  Do they work when the TAB is not connected to the tow vehicle?  If not you probably have a blown fuse in the tow vehicle.  If that is the case, the next question is why have the fuses blown?  If they blow when connected to the trailer then there must be a short somewhere in the trailer.

huanvanho

Hello Brad. Thanks for your suggestion. I have the attached wiring diagram from TAB. I have 12 VDC at tail running light Terminal 3. I do not know how to locate the ground wire for tail/running light. Can you give me a guidance where would it be?

Dutch061

Okay, on the diagram they list a "J Box" which I suspect is short for Junction Box where the pigtail from the 7 pin connector is joined to the trailer.

First I would visually inspect the wiring connections inside the Junction Box to make sure nothing is loose or disconnected. 

Next, in this box from Pin1 (as per the diagram) is the ground wire(s) and is installed on Terminal 7 in the J Box. It appears that this is a white wire.

You will need a test light and have the 7 pin connected to the TV. 

Step 1 would be to connect the ground of your test light to Pin 1 in the J Box
Step 2 would be to touch the probe to Pin 3 with the headlamps on on the TV, Pin 3 is the tail light circuit for the TAB

The light should light up, if it doesn't there is an open circuit. Since you have tested the TV with a tester, I am going to say the issue is on the TAB. 

From there you can turn on each turn signal and check the pins in the J Box that correspond to the left and right turn signals etc. 

Brad

huanvanho

Thanks for the suggestion Brad. However,  could not locate the J Box. They indicated it  mounted front of trailer. But I do not see it...  I found 1 box underneath the trailer in the attached photo. Can you tell me if this is the J-BOX ? Thanks

MuttonChops

huanvanho said:

. . . tell me if this is the J-BOX ? [see above post for image]

@huanvanho ; Yes, that is the Junction Box.

ScottG

Here's the inside of that junction box. The white wires from the last terminal on the right are the 12VDC negative grounds. One of the lower wires on that terminal runs via the pigtail to the 12V DC negative pin on your tow vehicle connector. One of the smaller upper wires on that terminal enters the trailer and runs all the way back past the converter and into the space behind the tail lights. 

My impression is that all lights are directly grounded back to the tow vehicle via the junction box and do not rely on any frame grounds to operate. 

Sharon_is_SAM

@huanvanho - in case no one has added this, the TaB has no back up lights.  Besides the ground wire, the Tail/running lights are wired to Terminal 3 or the third from the left in ScottG’s photo.

huanvanho

Thanks so much. I think I can fix it all your information. 

huanvanho

Inside the J-Box. I connected the tester's ground cable to terminal 7 (white wire) and I touch the tester probe to Terminal 3. the light came ON, so that mean I have power of the tail lamp to Junction Box. However, I still have no power to the license plate lamp or Tail light. I used the license plate lamp to power my rear camera when the head light is ON....  Can you recommend what I should look next? Thank you everyone.

Bayliss

@huanvanho, was the license plate light working prior to hooking up the camera?  Did it and the camera also work after the camera was installed?  If so, can you think of anything since then that may be contributing to the issue?

Assuming they were working at one point, there may just be a bad/loose connection that is associated with the camera installation.  That's where I would be looking since you have power at the J-box.  Maybe a ground wire connection is loose?

huanvanho

The camera was working before. Do you know where to look for ground wire?  I assume leaving terminal 3 at J-Box that is the + wire of license plate.  But I do not know how the wiring from terminal distributed. I would like to have a drawing of wiring from J box to the lighting.... perhaps the worst case I can run a new wires from J box to the license plate but that is a lot of works. Thanks for all the help.

ScottG

@huanvanho, reread my post of June 25. There is a negative (a.k.a. "ground") wire that runs from terminal 7 in the junction box all the way back to the tail of the trailer. I'll bet a nickel all the trailer's running lights are spliced into that wire.

Bayliss

@huanvanho, although it isn't specifically what you are looking for, the below discussion thread has a drawing of the connections in my J-box (2019 T@B 320 S Boondock Edge), but maybe it will be of some assistance to you.  I can't say for sure that the terminal connections are exactly the same as your 2017 model, but likely very similar.  I have never traced the wires back to their source(s), but check for the wire @ScottG mentioned above.

I don't know if you or someone else installed the camera, but if it were me, I would go back and check any wire connections between the camera and the license plate light.  Jiggle the wires while you and/or a helper are watching the light to see if it flickers on and off.

[QUESTION:  You mentioned your "headlights" in your original post.  What were you referring to?  Also, is it just the license plate light not working, or are your tail lights and/or running/side marker lights also not working?  Additionally, you mentioned the "reverse light."  Do you actually have a reverse light on your T@B, or are you referring to your tow vehicle?]

https://tab-rv.vanillacommunity.com/discussion/comment/128424#Comment_128424

huanvanho

Thank you all for your suggestions. I finally got it fixed. The Ground wire in terminal 7 inside the J-box was the main problem. After I reversed the screw on the terminal 7 and tight it back up... Everything starts working again. I have the tail light and license plate light back.  Again, Thank you' all for your expertises.  Specially, Thank you to Brad, Scott, Sharon and Bayliss