Troubleshooting an RV on a 2004 Ford E-450 Using 3035-P Wiring Adapter to Install Brake Controller

Published 07/14/2017

Question:

I recently purchased a brake controller harness 3035-P for a 2004 ford e450 motorhome. The tag on the harness says 3035. I see that there are a couple versions of the 3035a p and a s and I want to verify I was shipped the correct harness. There is power to the controller, however the display shows there is no trailer connected even though the trailer is connected. I want to make sure I have the right harness before I start searching for another issue. Also, in researching my issue I found the harness plugs into a brown plug near the firewall behind the parking brake pedal. The only brown plug I could locate is not an empty receptacle. The plug going in has one orange wire coming off. Is there another brown receptacle?

asked by: Greg

Expert Reply:

The # 3035-P wiring adapter is correct for a 2004 Ford E-450 cutaway like your RV is built on.

There are two similar connectors in the area behind the emergency brake. You want to use the one that has a blue, a red, and a green wire. I've linked a video of a brake controller install on a 2004 RV built on a Ford E-450. Skip ahead to about the 5:30 mark.

If the controller is installed properly and you're still not showing the trailer is connected you'll need to do a little testing. I would start at the motorhome's 7-way trailer connector and check the pin a the 5:00 O'clock position. Make sure it's clean and free of any corrosion. Also, check the corresponding pin in the 7 O'clock position on the trailer's 7-way for the same.

If the connector looks good you should check the pins on the adapter you plugged in under the dash. Make sure none are bent and just not making a good connection. You can also look inside the connector under the dash but it can be hard to see.

If you still can't find the issue let me know what results you've gotten and we'll keep troubleshooting.

expert reply by: Charles S