Hello everyone,

I've got a weird electrical issue with my Focus. When trailer is connected, the turn signals act up. Sometimes when using either turn signal it'll do sort of a "half" blink and will not blink anymore, unless I flip the lever again, then it works just fine. The issue is intermittent, meaning that sometimes it'll work just fine, other times it behaves as described where I have to flip the switch again. Same behavior confirmed with hazard lights. Turn signals/hazards work perfectly fine, when trailer is disconnected.

This was tested with 3 different trailers. The car exhibited the same issue with all 3 trailers, which leads me to believe that the problem is internal to the car, and not the trailer. And so I am at loss, and looking for some input from you guys.

My research of the issue thus far had been not very productive at all. The only thing that I found out is that most likely the issue lies within the GEM module. 

Thanks in advance for any help that I receive.

How was the trailer loom wired up?  Some connectors like skotch blocks can deteriorate with time and lead to intermittent open circuit, especially if they have bitten through too much cable.  Best to trace each cable back and test for continuity across the connector, flexing the cables to see if there is a weak point.  I had this on my car, with intermittent indicators and sure it is due my own bad installation, but never got around to doing anything about it.

2 hours ago, south_bound said:

How was the trailer loom wired up?  Some connectors like skotch blocks can deteriorate with time and lead to intermittent open circuit, especially if they have bitten through too much cable.  Best to trace each cable back and test for continuity across the connector, flexing the cables to see if there is a weak point.  I had this on my car, with intermittent indicators and sure it is due my own bad installation, but never got around to doing anything about it.

I am not sure as it was already installed when I bought this car. I appreciate your suggestion, and will definitely check it out.

I visually inspected the wiring and then performed measurements with a multimeter, everything checks out. Connections are solid, wiring looks fresh, nothing is worn or broken, there is continuity in all wires, there are good ground connections. Anyone has any other ideas?

I assume that this is not an official Ford trailer wiring harness. On a 2008 Focus the indicators for the trailer must be wired via some auxiliary relay as connecting the trailer indicators directly to the cars indicator circuit would cause all sorts of issues.

My guess is that hidden behind the trim panels somewhere near the back of the car will be an indicator repeater relay for the trailer. If the problem you have is intermittent then I would replace the relay.

16 hours ago, unofix said:

On a 2008 Focus the indicators for the trailer must be wired via some auxiliary relay

Its a few years ago, but I don't remember that on my 2007 Mk2 installation, though maybe something changed after that.  Just spliced the wires to each other for each of the lights, though did include an in-line buzzer that came with the kit to confirm trailer indicators working.  Maybe I did it wrong and got away with it?