OvalPiston

So I bought my Cayenne used, and it came with a trailer hitch and the 7-blade round adapter mounted directly next to the hitch.

My trailer is a tiny pull along, and it only has the four-wire (ground, running, left/brake, and right/brake) connector.

I bought an adapter at Harbor Freight P/N 69552, and it plugged in fine, and I have running lights.

BUT, I have no brake/turn lights.

I disconnected the adapter and measured the voltage directly on the car's 7 blade adapter. 1.8V constant, no changes whether the brake is on/off or a turn signal is blinking.

Turn signals/brake lights work fine on car.

Ideas?

marky522

If you dont have the trailer connected to the car you will not see any voltage difference. I wasted alot of time figuring that out one day. The Hitch control unit can detect when the trailer is connected. I would make sure that everything is completely seated and if it still persists I would try a different trailer or one of the testers you can buy that plug into the car and have lights to show each function is working. I have only ever had 1 Cayenne come in that actually had a problem with the car, all the others were issues in connections or the trailer itself.

Mark

OvalPiston

I jiggled the wires under the passenger side cover in the tail section. Voila! Turn signals started to blink!

BUT...no brake lights.

I hooked up a multimeter with the trailer cable off the converter, and with the turn signal on, the voltage varied between 7v and 4v.

Just no brake lights.

marky522

Can you post a picture of that area? It sounds to me like someone has added this trailer wiring using an aftermarket kit instead of the factory module. The biggest disadvantage to this that I see beyond the light issues is the factory module changes other things like how the transmission shifts when towing.

Mark

OvalPiston

It turned out that it was a genuine Porsche trailer hitch and control box that were installed, but my Porsche dealer found a problem with the control box which needed replaced and reprogrammed. $800 fix, $400 labor + $400 control unit. Working beautifully with LED lights now!

Billt Benneyan

Seems frequent frustrating forum topic. I have used 06 Cayenne S. All OEM tow hitch, transfer box, harness and 7 pin receiver. No trailer lights (incadesent NOT LED) with 4-pin adaptor plugged in. Process of elimination: confirmed independently trailer is fine. Replaced transfer box (twice!). Replaced harness. Replaced 7-pin receiver. Confirmed all functions going INTO transfer box are OK. Had RE-program. Checked all fuses.

I need a good electrical guy. I think I have answer. Want to test it.

I know LED trailer lights will cause an issue that can solved with a certain 4-pin adaptor dongle. But that’s not my issue

HOWEVER it suddenly occurred to me that prior owner installed tail lights assemblies with LED bulbs, so the LED issue is upstream of the transfer box.

im thinking 2 solutions:

1. Bag the OEM transfer box and just tap in a 4-wire to the lights as many folks do. I don’t regularly tow needed 7-pin but you never know. OR

2. Instead of feeding the transfer box from the plug in to the tail light assembly, pick up the signals on the tail light harness BEFORE it hits the LED unit.

thoughts?

19psi

It's a bit more involved than just tapping into the existing light wiring. You need something like a Curt trailer light controller which is very inexpensive. It taps into each light circuit and senses whatever lights are needed and then sends that power to the trailer lights through another isolated power lead. Since you're not using the vehicle's lighting circuits, the trailer lights won't overload them or cause dash warnings. For the power lead, I tapped off the wire going to the 12 volt power socket in the trunk, which is inches from where I mounted the controller. It's a hefty circuit with more than enough capacity to power any kind of trailer lights.

I used CURT 56146 3 to 2 converter. About $23 delivered from Amazon.

Pillow

Get rid of them and see what happens.

Adding: I have an extra 06 tow module, cheap, if you want to swap it out and see what happens.

sglougee

I am interested in buying let me know price.