Breakaway circuit not energizing brakes

[hardinrob]

Many thanks for the great information on this forum. Now I have a problem I have been unable to solve so far.

Problem:

Breakaway switch circuit not energizing brakes on 2014 Cherokee 274BH.

Supporting info:

Tow vehicle is 2012 Chevrolet Silverado with max trailering package, rated to safely pull trailer. Have safely pulled for thousands of miles in relatively flat areas of Texas. No plans to tackle mountains with current setup.

Troubleshooting steps within junction box at tongue:

Confirmed voltage is going to brakes when connected to tow vehicle and brake pedal pressed. Brakes energize.

Confirmed 12.7 volts to brakes when disconnected from tow vehicle and breakaway pin pulled. Brakes do not energize.

Guess is that it's a bad ground, but research shows each brake is grounded separately. Is there a common point where trailer brakes are grounded that, if open, would cause brakes to not work when powered from trailer battery?

Any other thoughts on why this failure is occurring?

Many thanks in advance for help diagnosing this issue. Safety is the top priority and I need to get this resolved. I'm a DIYer so I know exactly what has been done with no (or fewer!) surprises later.

[CHICKDOE]

i'm not sure exactly where you are taking the voltage measurements. but you say at the junction box on the tongue.

if the brakes ae energizing when connected to tow vehicle the grounding is ok.

in the junction box there will be a wire that runs down to the brakes that carries the 12 volt power. the brakes get grounded to the frame. there will be a ground connection in the junction box that will be connected to the frame (somewhere). so to operate the brakes while connected to tow vehicle the 12 volt power will come from the tow vehicle via the 7-pin cable, go down to the brakes, go to the frame, and then back up to the junction box and return to the tow vehicle via the 7-oin cable. this is working so the brake cabling between the junction box and the brakes is ok.

there will be a wire from the battery positive terminal up to the break-away switch and from there it will go to the junction where the 12 volt brake power from the tow vehicle joins the wire carrying that power down to the brakes. this wire will carry 12 volt power to the brakes from either the tow vehicle or the trailer battery. the trailer battery should be grounded to the trailer frame. thus the power is from the trailer battery up to the junction box, to the cable carrying 12 volt power to the brakes, then to the trailer frame and back to the trailer battery. this path will only operate when the breakaway switch is pulled. if you disconnect from the tow vehicle and pull the break away switch you should have 12 volt power at the junction of the tow vehicle brake power, the trailer 12 volt power after the break away switch, and the cable down to the brakes. this is where you need to take the voltage measurements.

hope this helps

[Flybob]

Is it by any chance using the original battery?

[5picker]

Originally Posted by hardinrob

Many thanks for the great information on this forum. Now I have a problem I have been unable to solve so far.

Problem:

Breakaway switch circuit not energizing brakes on 2014 Cherokee 274BH.

Supporting info:

Tow vehicle is 2012 Chevrolet Silverado with max trailering package, rated to safely pull trailer. Have safely pulled for thousands of miles in relatively flat areas of Texas. No plans to tackle mountains with current setup.

Troubleshooting steps within junction box at tongue:

Confirmed voltage is going to brakes when connected to tow vehicle and brake pedal pressed. Brakes energize.

Confirmed 12.7 volts to brakes when disconnected from tow vehicle and breakaway pin pulled. Brakes do not energize.

Guess is that it's a bad ground, but research shows each brake is grounded separately. Is there a common point where trailer brakes are grounded that, if open, would cause brakes to not work when powered from trailer battery?

Any other thoughts on why this failure is occurring?

Many thanks in advance for help diagnosing this issue. Safety is the top priority and I need to get this resolved. I'm a DIYer so I know exactly what has been done with no (or fewer!) surprises later.

How are you confirming the brakes do not energize when the pin is pulled?

[wanderingbob]

Have you pulled the pin and checked for voltage at the brake ?

[TacomaJoe]

I'd check the connection between the battery negative and the frame. With the brakes working when the TV is connected, I suspect that the 7-pin is providing the return path for the braking circuit. The hitch will also complete the path via the TV frame.

[wmtire]

Originally Posted by 5picker

How are you confirming the brakes do not energize when the pin is pulled?

X2. Are you manually spinning the wheels to see if the brakes work?

On a side note, several electric brake controllers have warnings to always make sure you have the trailers cord unplugged from the tow vehicle when testing the emergency breakaway switch so as to not backfeed the tow vehicles proportional brake controller, which can damage it.

[hardinrob]

Thanks for your responses.

I can hear the magnets engage when the truck is connected and the brake pedal is depressed. I also disconnected the trailer connection and tested the breakaway circuit while rolling in the driveway. Brakes did not engage.

In the junction box, I'm testing at the connection where the blue wire from the truck connection, and the blue breakaway lead, connect to the black wire that goes to the brakes.

I get voltage from either the truck pigtail or the breakaway switch when each is individually applied, but the brakes do not engage when the breakaway circuit is energized.

I too suspect a bad ground and that the ground pathway is being supplied by the truck pigtail when connected. The negative connection from the battery to frame is clearly visible and tight. Where else could the ground be bad?

This is really frustrating.

[CHICKDOE]

what you describe doesn't make sense, assuming you are testing to proper connection.

just for a double check, disconnect from the truck and then test the voltage at that connection both with the breakaway switch pulled and not pulled. this should verify that this connection is in fact intended to power the brakes.

it is also possible that the trailer battery is low and does not have enough power to activate the breaks, but you say it is supplying 12.7 volts. if so it should operate the brakes.

on our trailer there is a single wire that runs between the battery positive terminal and the junction box. this is connected to the 12 volt charge line from the 7-pin cable and is used to charge the battery while towing. this wire is also connected to one side of the breakaway switch. this allows battery power to reach one side of the breakaway switch. the other side of the breakaway switch is connected to the trailer brake wire. this wire is also connected to the brake wire from the 7-pin cable. i'd double check to make sue you have these wires properly identified. of course your trailer may be different but i suspect this is a pretty common configuration.

[Thomas ho]

start truck turn on headlights, pull forward , get out reach back ,yank controller wire as if trailer came loose from vehicle, make sure it clicks and stays out. try to drive away " fkrward" . if you can drive forward you NEED A NEW BREAKAWAY SWITCH. they dont last forever. moisture etc. way to much thought for a simple solution.

[hardinrob]

I absolutely agree, this makes no sense.

Breakaway switch is new. Testing confirms proper function. The trailer failed the suggested rolling test, as I indicated earlier.

I pulled the attached image from elsewhere on this forum. The diagram is my setup. I'm testing at the point indicated by the hand-drawn blue arrow.

The only explanation for me so far is a failed ground when the breakaway circuit is engaged. But where is it failing?

[bubbles]

Is it possible your brakes ground leads are not terminated to chassis ground and instead directly to the tow vehicle ground wire?

[Mike134]

Electrical troubleshooting is tough over the phone, almost impossible online.

I'd suggest read as much as you can to understand how the trailer brakes work both from the truck and the break away switch.

Then go to work troubleshooting. picture electricity flowing like water through a pipe that may help you.

[TacomaJoe]

Does the WHT GND wire from the J-box tie to the frame at the same point as the BLK NEG wire from the battery? Does the hitch light work without the 7-pin connection?

[NavyLCDR]

Originally Posted by TacomaJoe

Does the WHT GND wire from the J-box tie to the frame at the same point as the BLK NEG wire from the battery? Does the hitch light work without the 7-pin connection?

I would start there. The white wire from the 7-pin cable should also have a connection in the junction box to the trailer frame. The brakes' should also have one wire from each brake attached to the trailer frame (or one wire from each brake connected to each other and connected to 1 common point on trailer frame).

[TGR]

With the trailer plug disconnected from your tow vehicle, you should be able to read something near the battery voltage on the trailer’s 7-way plug between pins 1 and 2 when the break-away switch is activated. If you don’t have the proper voltage, then the connection at the wire nut shown in your diagram should be checked first.

If the proper voltage is present during the above test, then it’s likely a ground issue. You can run a temporary ground from the white wire nut to the trailer’s chassis and see if the trailer brakes now work. Hopefully, one of these ideas will identify the problem area.

[Larry-NC]

Could be a hidden break in the hot lead between the junction box and the axles. You've checked for 12v at the junction box. Check it at the axles. If nothing else, just poke a hatpin through the wire near the axles and check for 12v.

Also, get a long clip lead and check resistance between the ground at the axles and ground at the junction box. Could there be rubber bushings at the Torflex axles so the wheel ground wires need to go to the frame?

[chriscowles]

I personally experienced this problem last summer while on a long trip. By chance, I discovered that pulling the pin on the switch did not result in a closed circuit. I travel with a spare. It worked fine after I replaced it.

Put an VOM across the pigtails out of the switch and pull the pin. It should measure 0 ohms. If not, the switch is bad.

Take care that there is no voltage on the wires when testing.

Edit - Never mind. I see this sentence, now. : "Confirmed 12.7 volts to brakes when disconnected from tow vehicle and breakaway pin pulled."