My pop-up trailer - 2006 Starcraft is locking the brakes when I step on the brake from the truck. The wheels lock and the trailer skids, then rolls, then skids. Touching my brakes is like slamming the truck its so powerful, so its a full lock of the wheels. I've read many similar posts to this which gives me some ideas, but am still unclear which is likely my issue. Here's the full breakdown:Pulled the trailer 3-4 times this year with no issues. Took it camping this weekend. I think the emergency brake cord pulled when I unhooked and I put it back in at the time. When we left the campground, as soon as we were on the campground pavement the trailer brakes locked. I kept going and with every step of my brake, it locked the trailer. I pulled over, unplugged my trailer plug (round 7 way), disconnected the emergency plug and re-inserted. The problem was gone. We drove 120 miles home, no issues. Then, I hooked up last night and the whole thing happened again. I tried unhooking the emergency plug and the 7 way and reinserting again - but this time the problem didn't go away. I tried lowering the output to the brakes to zero, it didn't help. So the problem just started. I may have pulled the emergency plug when I unhooked the trailer, I can't remember for sure. But it was in when I pulled out from the campground.I have also tried lowering my output down to the lowest possible (zero) in my truck (09 Ford F150). It doesn't help. When I step on my brakes, the trailer brakes completely lock, then release (I can go a ways again), lock then release.I just replaced the fuses on my battery a couple weeks ago because they shorted out in the rain (I think). One of the wires has a quick disconnect (the green one, which I understand goes to the converter in the trailer). I am still not clear if the disconnect should be connected or unconnected when driving. And I'm not clear how the battery situation might cause this problem. Clearly the brakes get power. And it isn't just a bit of to much power, it feels like the emergency brake engages as soon as I tap my brake. If I had a short somewhere, which locations should I check?I am a newbie, and just figuring out the wiring in general of the camper and battery and still don't fully get the system. Thanks so much for any help!Jeff

Not knowing all circumstances. It is possible, that the first time you pulled the E brake pin out, and If the 7 pin was still hooked up. You possibly damaged the brake controller. Pulling the pin with the controller hooked up, "Can" damage the brake controller.

Hey Obie66, welcome to the forum.Could be a short between the brake lights and the brake wire for the trailer. Do you have a multimeter or a 12V test light that you can use to do some tests? Do you have a friend or relative that tows with a 7 pin that you could see if the problem occurs with their vehicle? That would at least allow you to focus on the tow vehicle or the trailer.You statedobie66 wrote: I pulled over, unplugged my trailer plug (round 7 way), disconnected the emergency plug and re-inserted. The problem was gone. JeffHow did you disconnect the emergency plug( breakaway switch)? As far as I know the only two parts to the emergency plug are the cable/pin, and a positive wire to the battery. Are you saying you pulled and reinserted the pin?Or did you disconnect the positive wire to the breakaway switch?If you pull the power wire for the breakaway switch does the problem go away?

I really question the controller at this point. It really does sound like the focal point. It is the only thing providing electricity to the brakes when the TV is applying brakes, if I understand your description of the behavior. What is the model of controller you are using?The break-away switch can be replaced easily for $25. The brake controller can be replaced for $120 with a good Prodigy, as needed.If you haven't already explored the brake system wiring on your PUP, it is pretty basic when laid out.Electric power for the brakes (electromagnets inside each brake, thus the need for electricity) comes from two sources: the TV's brake controller and 12v system, and the break-away switch with 12v from a battery on the PUP (either the main battery or a small, dedicated battery for the brakes).When the pin is pulled out of the break-away switch, this completes the circuit and allows the full voltage to activate the brakes. There will be no intermediate levels of braking - it will be full voltage/power and immediate. The wires leading to and from the break-away switch only carry the positive charge: one side comes from the positive terminal of your PUP's battery, the other side goes to the brakes. However, using the TV's brakes will have no affect on this system. Only when the pin is pulled out will it activate.The brake controller in the TV, as you are acquainted with from your description, provide proportional power to the PUP's brakes through the 7-way connector. As you mention, you can dial this up or down. Activating the level partially should apply some voltage and more voltage is applied as you move the lever further to max.What happens when you slowly activate the manual lever on the brake controller? Does it lock up or is gradual braking applied?As opnspaces asks, if the break-away switch is not connected to the battery, do you still have the problem? If so, it should have nothing to do with the break-away switch at this point. It's in the controller and/or wiring.And Terryallan hits upon what I think is the culprit, in that the TV's brake controller was connected when the break-away switch was activated, sending an electrical charge back into the controller, likely scrambling it.Let us know how you progress, so we can all learn. And good luck hunting this down. Like I said, there's only a few components to deal with so it's a matter of ruling them out.

First of all, let me just say I *love* this forum. I'm a PUP newbie this year, and the content here from past posts has helped me through a lot of questions without ever having to ask. So thank you all for such kind knowledge sharing.I am already so much more knowledgeable than I was a day ago, just by this thread.Its going to take some troubleshooting, and my first available daylight time is not until Saturday, so this gives me a lot to start with, but I won't have many answers as to what I've learned until then, so standby!opnspaces - I do have a voltmeter - how do I look for a short between brake wire and brake lights? Great idea to test with a friend's, but unfortunately I don't have anyone locally that I can do this with.opnspaces wrote:How did you disconnect the emergency plug( breakaway switch)? As far as I know the only two parts to the emergency plug are the cable/pin, and a positive wire to the battery....If you pull the power wire for the breakaway switch does the problem go away? Yes - I just pulled and re-inserted the pin. I will also try pulling the power wire on the breakaway. bondebond - I attached a picture of the controller - it is a digital controller built into my truck as an option from Ford. When I squeeze the two manual levers together, it replicates the same problem - a locking effect. Dialed down to zero, doesn't help, and its hard to tell what dialing up does because it feels like a full lock from the beginning. According to the Ford manual, this thing is supposed to detect brake module faults and wiring faults. I discovered in the owners manual that there is a series of digital indicators on this controller that I need to troubleshoot too. I haven't explored the wiring underneath too much - on my troubleshooting list - what should I be looking for? Exposed wiring that could cause a short I guess?bondebond wrote:And Terryallan hits upon what I think is the culprit, in that the TV's brake controller was connected when the break-away switch was activated, sending an electrical charge back into the controller, likely scrambling it.Hmmm. It is possible I disconnected the break-away pin by hand with the brake controller still plugged in, but I can't remember. Thank you all for all of this great info. I am anxious to fix and troubleshoot this with another camping trip planned weekend after next!

There are a few things you can check, but I'll start by saying that now that we know you have a built in factory controller, if you can figure out how to check fault codes I would go there first.Above is an image of the vehicle side of the 7 pin connector. The left side image is looking into the pin connector on your tow vehicle. First thing is to ignore the center pin as it's for backup lights. Now look at the blades arranged in a circle kind of like the numbers on a clock. You will notice that the 11 o'clock blade is for a brown wire which is the tail and running lights. 1 o'clock is black wire 12V positive, 5 o'clock is your blue brake wire and 7 o'clock is your white ground wire. You might by now also have noticed that there is no brake light wire for the trailer brake lights. This is because when you put on the brakes your tow vehicle basically just turns on both turn signals but doesn't let them flash. So your brake light wires are actually both the green 3 o'clock and the yellow 9 o'clock terminals.Set your meter to 20v dc volts (or just dc volts if you have an auto ranging meter). Apply the parking brake and block the wheels on your tow vehicle. Now turn on the ignition but don't start the engine. Now put the black probe on the 7 o'clock blade and the red probe on the 1 o'clock blade. You should get battery voltage. Write down or remember this number. Now move only the red probe and check all the other pins. You should get no voltage on any other pin.Assuming that the above tests are good, turn on the running lights and measure from the 11 o'clock pin (brown tail running lights) to the 7 o'clock pin (White ground) You should get battery voltage with this measurement or pretty darn well near battery voltage. Now keeping the black probe on the 7 o'clock ground pin, move your red probe down to the 5 o'clock (blue brakes) pin. You should have no voltage on this pin.Assuming that the above tests are good, turn off the running lights and turn on the left turn signal so it flashes. Now measure from the 9 o'clock pin (yellow left turn) to the 7 o'clock pin (White ground) You should get flashing battery voltage although many meters are not quick enough to display this so if the numbers jump around it's probably good enough. The important part is the next measurement. . Keeping the black probe on the 7 o'clock ground pin, move your red probe down to the 5 o'clock (blue brakes) pin. You should have no voltage or flashing voltage on this pin.Repeat the above test using the 7 o'clock ground and the 3 o'clock green terminal and the blue 5 o'clock terminal.If you get no voltage on the blue 5 o'clock brake wire for any test you are probably good with no shorts on the brake light wiring on the vehicle side.Turn off the turn signals and running lights and get a helper. If you don't have a helper handy, turn off the ignition until you can get a helper. Keep the engine OFF, but the ignition on so the warning lights are all illuminated on the gauges. place a helper in the drivers seat and go put your black probe on the 7 o'clock ground and the 5 o'clock blue terminals. You should have no or extremely little voltage. Now have the helper just barely move the two squeeze levers together until you get a voltage reading. Did the voltage jump straight up to 9 volts or more? The voltage should ramp up as the levers are squeezed further and further. If the voltage jumps from 0 to 9+ volts with all lights off and no brake pedal pushes, then you most likely have a controller fault. If the voltage seems to ramp up smoothly with the lever being moved, you controller is probably okay. Just as a check have the helper let go of the levers and step lightly on the brakes until the lights come on. You should get voltage, but probably not more than 1.5 volts as the lights come on.

Trailer brakes lock when I brake from the truck

13 Replies

obie66
Explorer
Jun 26, 2013
Camping up at Mt Rainier this weekend!
opnspaces
Navigator III
Jun 26, 2013
Thanks for keeping us updated as to the status. Hopefully the trailer brakes work well now.

In looking at the tech notes it's interesting that so many fuses were blown but no diagnostic trouble codes in the controller. I have no idea what BTC is but I'm guessing (Body ?? Computer) and the TBM is the Truck Brake Module?

Anyway at least they have replaced the module and the plug so hopefully you can go camping again.
obie66
Explorer
Jun 26, 2013
Well, its back and all working great. Below is the full analysis from Ford service - some of which doesn't totally add up. The blown fuses and non-working lights were not an issue initially (I had all lights, blinkers, brake lights - but it is true that when I took the multimeter to it on Saturday, I was not getting reading - so maybe it just all went downhill in a short period. The other odd thing was the replacement of the trailer plug - indicating it was broken with corrosion. They had to replace that after replacing the controller. Here's the diag:

No lights to trailer. Found no DTC for BTC. Found 3 fuses f82, f58, f31 and one relay (#6 and 1 blown fuse. All lights working. TBM shows trailer not connected. Went symptom test. Found TBC module not sending correct voltages to plug.. Replaced TBM. Truck is currently working properly at this time. Checked trailer malfunction in the plug. Disassembly of plug found broken and corrosion. Need to replace plug in trailer. Installed new trailer plug. Now system is working properly.
bondebond
Explorer
Jun 25, 2013
I'm glad you were able to hone in on it fairly quickly. You wouldn't expect something new to have a problem, but it happens. Hope it's an inexpensive fix, too. Let us know the outcome.
obie66
Explorer
Jun 25, 2013
Sorry for the delayed response. You all had me on the right track and saved me a lot of time troubleshooting wiring on the trailer. It was the controller. On Saturday morning I tried the voltmeter tests. I was getting totally inconsistent results. No reading on the initial battery voltage test, full reading on the running lights, nothing on the brake test. There were inconsistent readings and didn't have complete confidence in my multimeter, but it seemed the controller was not sending any power. So I hooked up and tried to drive, and my issue of locking was gone. That is because it wasn't applying any brakes. I tried raising the level, and the controller indicated "no trailer". So definitely the controller. I took it into Ford and they have confirmed it was causing shorts. I will post the full diagnosis when I get it back.

Thanks again for all of your help. I seriously would have been trying to chase wiring on the trailer shorts without this post because I just assumed being a fairly new truck and controller that it wouldn't be that.
obie66
Explorer
Jun 20, 2013
Wow - opnsspaces, this is *awesome* I can't wait to do these tests Saturday morn and see where it leads me! Thank you!!
obie66
Explorer
Jun 20, 2013
Wow - opnsspaces, this is *awesome* I can't wait to do these tests Saturday morn and see where it leads me! Thank you!!
obie66
Explorer
Jun 20, 2013
Forgot to post the controller pic.
opnspaces
Navigator III
Jun 20, 2013
There are a few things you can check, but I'll start by saying that now that we know you have a built in factory controller, if you can figure out how to check fault codes I would go there first.

Above is an image of the vehicle side of the 7 pin connector. The left side image is looking into the pin connector on your tow vehicle. First thing is to ignore the center pin as it's for backup lights. Now look at the blades arranged in a circle kind of like the numbers on a clock.

You will notice that the 11 o'clock blade is for a brown wire which is the tail and running lights. 1 o'clock is black wire 12V positive, 5 o'clock is your blue brake wire and 7 o'clock is your white ground wire. You might by now also have noticed that there is no brake light wire for the trailer brake lights. This is because when you put on the brakes your tow vehicle basically just turns on both turn signals but doesn't let them flash. So your brake light wires are actually both the green 3 o'clock and the yellow 9 o'clock terminals.

Set your meter to 20v dc volts (or just dc volts if you have an auto ranging meter).

Apply the parking brake and block the wheels on your tow vehicle. Now turn on the ignition but don't start the engine. Now put the black probe on the 7 o'clock blade and the red probe on the 1 o'clock blade. You should get battery voltage. Write down or remember this number. Now move only the red probe and check all the other pins. You should get no voltage on any other pin.

Assuming that the above tests are good, turn on the running lights and measure from the 11 o'clock pin (brown tail running lights) to the 7 o'clock pin (White ground) You should get battery voltage with this measurement or pretty darn well near battery voltage. Now keeping the black probe on the 7 o'clock ground pin, move your red probe down to the 5 o'clock (blue brakes) pin. You should have no voltage on this pin.

Assuming that the above tests are good, turn off the running lights and turn on the left turn signal so it flashes. Now measure from the 9 o'clock pin (yellow left turn) to the 7 o'clock pin (White ground) You should get flashing battery voltage although many meters are not quick enough to display this so if the numbers jump around it's probably good enough. The important part is the next measurement. . Keeping the black probe on the 7 o'clock ground pin, move your red probe down to the 5 o'clock (blue brakes) pin. You should have no voltage or flashing voltage on this pin.

Repeat the above test using the 7 o'clock ground and the 3 o'clock green terminal and the blue 5 o'clock terminal.

If you get no voltage on the blue 5 o'clock brake wire for any test you are probably good with no shorts on the brake light wiring on the vehicle side.

Turn off the turn signals and running lights and get a helper. If you don't have a helper handy, turn off the ignition until you can get a helper.

Keep the engine OFF, but the ignition on so the warning lights are all illuminated on the gauges. place a helper in the drivers seat and go put your black probe on the 7 o'clock ground and the 5 o'clock blue terminals. You should have no or extremely little voltage. Now have the helper just barely move the two squeeze levers together until you get a voltage reading. Did the voltage jump straight up to 9 volts or more? The voltage should ramp up as the levers are squeezed further and further. If the voltage jumps from 0 to 9+ volts with all lights off and no brake pedal pushes, then you most likely have a controller fault. If the voltage seems to ramp up smoothly with the lever being moved, you controller is probably okay. Just as a check have the helper let go of the levers and step lightly on the brakes until the lights come on. You should get voltage, but probably not more than 1.5 volts as the lights come on.
obie66
Explorer
Jun 19, 2013
First of all, let me just say I *love* this forum. I'm a PUP newbie this year, and the content here from past posts has helped me through a lot of questions without ever having to ask. So thank you all for such kind knowledge sharing.

I am already so much more knowledgeable than I was a day ago, just by this thread.

Its going to take some troubleshooting, and my first available daylight time is not until Saturday, so this gives me a lot to start with, but I won't have many answers as to what I've learned until then, so standby!

opnspaces - I do have a voltmeter - how do I look for a short between brake wire and brake lights? Great idea to test with a friend's, but unfortunately I don't have anyone locally that I can do this with.

opnspaces wrote:
How did you disconnect the emergency plug( breakaway switch)? As far as I know the only two parts to the emergency plug are the cable/pin, and a positive wire to the battery....If you pull the power wire for the breakaway switch does the problem go away?

Yes - I just pulled and re-inserted the pin. I will also try pulling the power wire on the breakaway.

bondebond - I attached a picture of the controller - it is a digital controller built into my truck as an option from Ford. When I squeeze the two manual levers together, it replicates the same problem - a locking effect. Dialed down to zero, doesn't help, and its hard to tell what dialing up does because it feels like a full lock from the beginning. According to the Ford manual, this thing is supposed to detect brake module faults and wiring faults. I discovered in the owners manual that there is a series of digital indicators on this controller that I need to troubleshoot too.

I haven't explored the wiring underneath too much - on my troubleshooting list - what should I be looking for? Exposed wiring that could cause a short I guess?

bondebond wrote:
And Terryallan hits upon what I think is the culprit, in that the TV's brake controller was connected when the break-away switch was activated, sending an electrical charge back into the controller, likely scrambling it.

Hmmm. It is possible I disconnected the break-away pin by hand with the brake controller still plugged in, but I can't remember.

Thank you all for all of this great info. I am anxious to fix and troubleshoot this with another camping trip planned weekend after next!