Troubleshooting Lack Of Running Light Signal While Towing A Mini Cooper

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Question:

Have a Mini with led lights. And a Sprinter based Winnebago View. Bought an adapter from you for the connection. Worked great- drove to SW Florida- 5-60 miles. Taillights stopped working- only directional and brakes. Got ready for our next trip— nothing. Had to buy rooftop lights naturally, cords beat up roof- but that’s my problem. Can you solve the connection issue?

asked by: Mike A

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Expert Reply:

Hi Mike,

If a specific signal isn't coming through to the towed vehicle or trailer then the first place to start would be the tow vehicle's trailer connector. It's super common for the trailer running light fuse to blow in the tow vehicle and not know. I would check the running light pin with either a multimeter # PT89ZR or circuit tester # PTW2993 to see if it's getting power. If not, then the fuse is likely blown.

If you do have power then you'll just keep working your way forward testing at each connection point to see where the power is dropping off. Let me know what you find and we can keep troubleshooting.

expert reply by: Kevin C

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7-Way Wiring Diagram
(click to enlarge)

Mike A.

9/16/2024

I was told that a meter doesn’t demand sufficient draw to get the trailer connector to respond. I’ll look for the fuse and try again. Can you at least confirm that I bought the right converter and it should work?

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Kevin C.

9/17/2024

@MikeA We're just testing to see if you even have any power running to the pin to begin with. Using a tester like the # PTW2993, which has an incandescent light in it would give you the load you need.

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Mike A.

9/16/2024

Kevin. I replaced the fuses as you suggested. I would still like to confirm I have the right part. The one I have is one piece- plugs in between the rig and the towed vehicle. I see another on your website by Curt that is two pieces connected with a wire. Do I have the wrong part???

Reply

Kevin C.

9/17/2024

@MikeA How exactly do you have the Mini connected to the motorhome? Did you use diode wiring to connect to your tail light wiring or a plug-in kit. With only the running lights being affected it leads me to believe that the wiring for the running light circuit either is damaged or the spade terminal could just be loose on the diode and need to be pressed in more. You can also check the wiring at the 6-pole socket at the front of the Mini. If the terminal wasn't tightened enough the wire for the running light circuit could have slipped out from road vibration. I typically fill the boot that encases the back side of the socket with RTV sealant to help keep the wires from loosening or corroding. The adapter likely isn't the problem here, but you can test the wiring to see if power is coming through. If you only have it coming into the adapter and not out then the adapter is the problem. You could also eliminate the adapter by jut splicing in resistors # DI34ZR on the RV wiring running up to the diode. They have to be before the diode otherwise the resistors would be getting power when you aren't flat towing.

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Mike A.

9/18/2024

@KevinC Sorry- the car is connected by a 7-6 pin cord to the adapter whisch is plugged in to the rv’s 7 pin socket. I’ll get the proper tester and start from there.

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Mike A.

9/18/2024

@KevinC Which tester would be best- - most come with a grounding clip- do I just ground that to the frame? Ther is also a cordless one that looks good- —

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See All (12) Replies to Mike A. ∨

Mike A.

9/23/2024

Bought a test light. Could only find current on the positive blade of the motor home. Plugged in a 7/4 adapter and a set of trailer lights and they worked. Tried to find current with the reset on the 4flat day and couldn’t get consistent results. Tried the tested on my pickup’s trailer outlet and it worked perfectly. Next steps- clean contacts and try again?????

Reply

Kevin C.

9/24/2024

@MikeA While testing do you have the light function light (i.e. turn signal on) on? Otherwise you will not see anything with the tester. If you connected a 7 to 4 adapter and the lights worked then we know the signal is coming through but the pins could just not be making good contact with the trailer cable. I would clean the pins out if there's any debris and coat them in dielectric grease # 11755 to protect them from corrosion. You might also need to use a small flat head screw driver to bend the contact pins back into place a bit. Plugging and unplugging the cable over time can eventually wear on the contacts and even push them slightly out of place, requiring you to just bend them back a bit to make better contact.

Reply

Mike A.

9/25/2024

@KevinC Yes- had function on. But good question. I’ll try cleaning them.

Reply

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Troubleshooting Lack Of Running Light Signal While Towing A Mini Cooper

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