Trailer connector problem

[Pahaska]

I bought a set of battery-operated wireless tow lights for use in the Smart under tow. The transmitter plugs into the 7-wire socket, under the AI rear end.

The lights are on at low intensity and serve as running lights whenever they are switched on. The transmitter connects to three wires in the AI connector: ground, left turn, and right turn. I have tested the transmitter on the bench with a 12v power supply and the lights work perfectly.

When plugged in to the AI, the brake lights operate properly, indicating signals on both left and right turn pins. However, the turn signals do not work unless I have my foot on the brake. Then, they work properly with one half at hi-intensity while the other half blinks. If I take my foot off the brake, there is no reaction to the turn signals.

It appears that the left and right turn pins in the AI connector do not pulse unless I have my foot on the brake.

Has anyone encountered anything similar?

[73shark]

It might be caused by the module that detects burned-out bulbs. I've read in other threads and/or forums that switching to LED bulbs can cause problems.

[garry]

This may not help but give you an idea.

I had the problem and install isolation diodes it has been so long ago I can't remember how I connected the diodes to fix the problem. Didn't have LED's but same principle.

Found this there is a diagram further down the post I don't think I used but 2 diodes but there is info so you can understand the problem (IF that is your problem).

https://www.oznium.com/forum/topic15397

[Pahaska]

Thanks, but the diode fix is for a different problem.

I posted a query on the Sprinter Forum just now. I see some pretty sophisticated trailer wiring posts there. Hopefully, someone there can put me straight.

I worked with prototype hardware for IBM for 35 years, but this has me stumped at the moment. If the Sprinter forum doesn't pay off, it is under the rig with a trouble light for me.

[Pahaska]

73Shark was right. I did a search on the Sprinter Forum. I had to look at over a hundred threads until I found this:

From the Sprinter Forum: OK, I had something similar when I attempted to hook up some LED trailer lights to my moto hauler. I was told that because the low draw of LED's the van thinks that a bulb is out? It was suggested that the dealer can make some adjustment to the ECU that can trick or bypass the van into thinking the lights are fine. I did not fight it and went with regular bulbs lights. No need for a trip to the dealer just for lights but I do plan on asking when I take it in for the first service.

From a following post: There are documented factory instructions on how to deal with led lighting.

I'll call Mercedes in Round Rock tomorrow and see what they suggest.I'll be there for service before any really long trips towing the Smart. If it is a lot of trouble, I'll just fit a couple of resistors in the male connector.

[NOLA_russ]

Originally Posted by Pahaska

73Shark was right. I did a search on the Sprinter Forum. I had to look at over a hundred threads until I found this:

From the Sprinter Forum: OK, I had something similar when I attempted to hook up some LED trailer lights to my moto hauler. I was told that because the low draw of LED's the van thinks that a bulb is out? It was suggested that the dealer can make some adjustment to the ECU that can trick or bypass the van into thinking the lights are fine. I did not fight it and went with regular bulbs lights. No need for a trip to the dealer just for lights but I do plan on asking when I take it in for the first service.

From a following post: There are documented factory instructions on how to deal with led lighting.

I'll call Mercedes in Round Rock tomorrow and see what they suggest.I'll be there for service before any really long trips towing the Smart. If it is a lot of trouble, I'll just fit a couple of resistors in the male connector.

This is what worked for me:
https://www.etrailer.com/Wiring/Tow-Ready/TR20141.html

[Pahaska]

Originally Posted by NOLA_russ

This is what worked for me:
https://www.etrailer.com/Wiring/Tow-Ready/TR20141.html

Perfect. Thanks.

I just ordered one of those. I'll move the transmitter into a separate box with a short pigtail to a 4-pin connector to plug into this 7-pin connector. I'll mount magnets on that box to hang on the metal floor near the hitch for a nice, clean installation.

I can unplug the transmitter if I want to pull a small utility trailer with a 4-pin connector.