Trailer wiring help

[slammer]

Newer Shorelander trailer w/surge brakes. Switched out the last couple feet of the wire harness with one of those 7 wire round molded plugs. Checked it all out before the soldering and shrink tube wrap and everything works good except the brakes don't release when backing up. Have done 5 of these over the past few years and no problems. This one has me stumped. Any ideas? Thanks

[icehole10]

If the trailer has surge brakes that should have nothing to do with the plug, or wiring harness, or anything electrical. Surge brakes are hydraulic and are engaged by the force of the trailer pushing against the truck. The harder you break the more force that is put against the tongue, there fore more brake application. I would have to say you've got something wrong with that part of your trailer. Do a google search for "reverse brake lock out for surge brakes" and see if that helps you out.

[Hoey]

The purple wire, according to my wiring diagram should be connected to the backup lights. When the tow vehicle is in reverse, the brakes are released.

[slammer]

They still need power to release when backing hence the plug. It worked fine before i switched plugs. Must be something with that new plug. Having it looked at tomorrow.

[icehole10]

Then you must have electric over hydraulic brakes, not conventional surge brakes. Conventional surge brakes require no electric signal from the towing vehicle, and are 100% hydraulic. If you unplug your trailer harness, and back up, I assume they then release?

[slammer]

Had one wire wrong. Its not blue wire to blue, its blue to yellow on this plug. Plug connectors are not the same as the truck. Thanks for the help.

[Pat K]

Then you must have electric over hydraulic brakes, not conventional surge brakes. Conventional surge brakes require no electric signal from the towing vehicle, and are 100% hydraulic. If you unplug your trailer harness, and back up, I assume they then release?

Almost all trailers with surge brakes manufactured in the last 10 years use the back up light power through the 5 pin flat or 7 pin round connector to disengage the surge brakes when backing up the trailer. If you unplug the harness the brakes will definitely lock up if you try to back up the trailer.

[Kyhl]

Almost all trailers with surge brakes manufactured in the last 10 years use the back up light power through the 5 pin flat or 7 pin round connector to disengage the surge brakes when backing up the trailer. If you unplug the harness the brakes will definitely lock up if you try to back up the trailer.

It is probably been longer than 15 years. My 2004 has this. There is a relay in the tongue that is triggered off the back up light. The relay bypasses the hydraulic lines so that the master cylinder is not able to pressurize the brakes.

Not speaking to anyone in particular, if you have surge brakes and the connector has 5 pins, use them all. It will save you from having to manually lock out the tongue when you back up.

[ZapBranigan]

Yep the old blue wire. I found that on most landing if you take it easy you could get away with it (I unplugged wires to save bulbs) The down hill created enough pull on the trailer to offset the foece between vehicle and trailer. Now I have LED so I don't need to disconect the wiring and the Blue wire becomes important again.

Blue = Back up lights 5 pin.