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sprinkles08, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 21436
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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No left turn power in trailer connector, 2014 sprinter 2500

Customer Question

no left turn power in trailer connector
JA: What is the model/year of your Mercedes?
Customer: 2014 sprinter 2500 navion motorhome
JA: How many miles are on the car? Is it an automatic or a manual transmission?
Customer: 10,000 automatic
JA: Are you fixing your Sprinter 2500 yourself? What have you tried so far?
Customer: I have all other functions working in the 7 pin connector
JA: Anything else you want the mechanic to know before I connect you?
Customer: that all
Submitted: 1 month ago.
Category: Mercedes
Customer: replied 1 month ago.
I am testing the original towing trailer/towing wiring harness on my Mercedes Sprinter so that I can tow a small vehicle behind my motor home. When I tested the trailer connection at the hitch of the Sprinter, the left turn signal does not work. The left turn signal, in the trailer connection, only works when I press on the brake.
Customer: replied 1 month ago.
I have mapped out the connections on the Sprinter trailer connector. There are ten pins in the connector. Looking at the connector with the locking clip on the top, starting at the top left and working right:(1) (2) (3) (4) (5)(6) (7) (8) (9) (10)(1) Running/marker lights
(2) 12V +
(3) Ground
(4) Right turn [When left turn signal is on and brake is applied, this becomes brake light/solid light]
(6) Brake [When left turn signal is on and brake is applied, this becomes left turn/flashing]
Expert:  sprinkles08 replied 1 month ago.

Hello and welcome to JustAnswer!

If the wiring is factory then it appears you may have a bad trailer lighting module. The module supplies power on the lighting circuits for the turn signals based on a communication bus message. The brake and turn signals are controlled on the same wire, they're powered constantly for brake and pulsed for turn. The black/white wire is left brake/turn, black/dark green is right. Are these the colors you're seeing?