Trailer's reverse lock out help

Linecapt · **Posted:** Tue Aug 05, 2014 6:11 am

Ok, have a new to me '05 Four Winns bunked trailer, with the 70LP surge brake on the trailer coupler. Since it doesn't come with a manual, looking for guidance on how it's SUPPOSED to work. So I have the 5 wire trailer wiring attached, sending power on the blue wire to the master cylinder actuator when placed in reverse. I presume, when this happens, a actuator is supposed to engage to lock the trailer from braking up while pushing in reverse, hence the pressure on the hitch as if you're stopping. Now it also has a manual lockout that you can place the pin in the slide to get the same reaction. But my problem I found is, even after just getting the trailer back from being serviced (and with a new master cylinder) that it still locks up in reverse, after trying to push up a slight grade going up my driveway after about 150' without the pin.

So, am I supposed to put the pin in everytime I back up or is the actuator supposed to do it for me? Thank you all in advance.

Surface Interval · **Posted:** Tue Aug 05, 2014 6:36 am

I have found that if the coupler/brake actuator is not fully extended the reverse lock out will not engage. I have gotten into the practice of coming to a stop, then pull forward a bit more to extend the coupler. This may be enough to make it work for you. Because of the gradual slope of the area I use, I have used a different method. After stopping and while moving forward maybe 1-2 mph I shift the truck to reverse. This engages the lock out and allows me to back up. You may have to pin it if these ideas don't work for you. Hope this helps.

Cap'n Morgan · **Posted:** Tue Aug 05, 2014 6:37 am

I have to put the pin in on our EZLoader trailer every time I back up on the slightest irregular terrain, hill or our yard.
A pain, but manageable.

LouC · **Posted:** Tue Aug 05, 2014 7:13 am

There are 2 different kinds of solenoids: one is a blocking solenoid that stops hydraulic pressure from leaving the master cylinder; the other actually relieves the hydraulic pressure by dumping it back in the master cyl reservoir. The former requires that you pull forward before backing, the latter does not.
I have stuck with free backing drum brakes partly for this reason. Drum brakes get a bad rap because the wheel cylinders can seize up but with a minor modification that does not happen nearly as often and they will stop well, even better than discs on lighter trailers .

schoolsOut · **Posted:** Tue Aug 05, 2014 7:31 am

I have the same master cylinder as you and I replaced mine myself a couple of years ago. If memory serves me, our MC bypasses the brake system when in reverse by dumping the fluid back into the MC. I have had issues backing up at one point because a fuse had blown in my truck due to some worn wires in the trailer harness. The back-up lights on my Tahoe still worked which caused this to be a little confusing for me at first and led me to believe something was wrong on the trailer side of things. Then I discovered that my truck has separate fuses for trailer lighting. My trailer B/U light fuse had blown. I replaced this along with the wiring from the plug back through the tongue. Maybe you have something like this going on? You could use a test light to make sure that you are getting current to the B/U terminal on your truck. I believe this is the center terminal. If you don't have problems there, maybe the reverse lockout solenoid is bad.

You should not have to use the pin to back-up. That is only needed if you have a problem.

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

Anther thing is that these solenoids are known to fail frequently.

230 Mike · **Posted:** Thu Apr 30, 2015 1:49 pm

Old post, but in case it's of any value - Lou's description is correct and in the case of the OP's trailer, the solenoid is of the 2nd type he described. When the solenoid activates, all it does is open a valve (internal to the solenoid) allowing brake fluid to return to the master cylinder rather than pressurize the brake lines.

And these solenoids aren't terribly reliable. I'm on my 3rd; the original one failed before the end of the first season. The 2nd lasted 8 years and still wasn't completely out, but was beginning to go.

I posted some pics on this thread long ago, in case it's of any help with the LP70 or LP7000 actuator:

viewtopic.php?f=12&t=6235&p=60390#p60390

www.iFourWinns.com

Trailer's reverse lock out help

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