Trailer wiring Question - No Left Turn Signal in wiring from Chassis on 2007 Monaco Caymen.

[Alan Penniman]

Hello Everyone,

My 2007 Cayman is having problems with the Trailer Plug and the Left turn / Brake signal.  Whom ever wire the added tow light system did a hack job.  They hacked in a 4 pin connector and they also ran a wire from the left turn signal to the red wire of the trailer plug.  Since the 7 way plug was broken and the 2 foot cable run back to the 6 way plug under the rear end was in sad shape.  I decide to replace the plug and the short harness.  

I got every looking good again, except I found why they hotwired the left turn signal to the red wire.  The Left Turn / Brake signal coming from the chassis wiring is not working.  Their hotwire allowed the blinker to work, but the brake light is not working.  I can't run another hotwire from the brake light because it will fight with the brake signal.   

I tried to go through the wiring diagrams I got off the internet from Monaco, but I am having a hard time finding the actual trailer collector in them so that I can follow it back to the next point and find where that point is physically on the motor home.  

I don't mind running a wire from the front back to the plug, but I am not sure where it would tie in.  I tried following the existing wire backwards. and Got past the mud flap and went up (and up and up and up).  I couldn't see where it went once it got over the frame near the transmission. 

Has anyone one else run into a similar problem? How did you fix it? Where are the tie in points for the combo signal? I saw there were a couple of relays, but the wiring diagrams did not identify them so that I could locate the physical units. 

Thanks 

 

Alan 

 

Edited April 29, 2022 by Alan Penniman

[Trinidaddave]

It's impossible to trace the wires  from front to back by hand.  Pick up a cheap signal tracer on Amazon, inject the signal abuse the tracer to locate it in the electrical system.  You will find an open if one exist.

[cbr046]

Our Endeavor has a box at the hitch to adapt to a 4-wire system.  I don't know if a PO installed it or if it was OEM. 

If all else fails you could use the "hack job wiring" with steering diodes to power the LH toad light.  I'll try my hand at ASCII graphics . . . .

Coach LH Brake Light-----|>|----\

.                                                    |------- Toad LH Brake/Turn

Coach LH Turn Signal-----|>|----/

Diodes only allow so much current before the smoke leaks out, and they will smoke with a nanosecond of overcurrent, so they must be sized appropriately, be fused or have overcurrent protection in case of a short.

Of course, there are companies that make these professionally (better idea).  Here's an example from etrailer.com - https://www.etrailer.com/Accessories-and-Parts/Roadmaster/RM-790.html

Take this solution with a grain of salt.  It's not the most elegant . . .

- bob

[lake49068]

My Neptune had a similar issue and the coach has a fuse box in a rear compartment with a bunch of fuses protecting the lines going to the "trailer" plug.  Check to see if you have a similar set up.

[Alan Penniman]

Hi Everyone 

 

I just wanted to update everyone on this problem.  I was able to finally get it working!

I was able to get the wiring diagrams from the web and I used a trail version of Adobe Acrobat and lots of scotch tape to enlarge them to 44 x 25. 

I found that the Left Turn Combo signal had fuses and relay and that it was on a small sub panel.

I went back to the front electrical cubby where the large fuse panel was and found that there was another smaller panel that did have fuses and relays for the turn indicators.  When I popped the cover off that panel, one of the relays popped out.  It was the left signal relay!  I popped it back in and tried the blink and it was not blinking (I just passed state inspection this morning so I knew it should be).  I went out back and remove the hotwire that someone had put in place prior to me owning it and presto!  It was working, directionals and brake combo.  Some tech had just jumped in a wire instead of doing some checking!  

Thanks for all the input and help.  Maybe this can help someone else in the future.