Trailer Brakes

[marpel]

As per another thread, I have yet to change out the 7 pin cable.

Prior to doing so, I decided to confirm whether the old cable is still usable.

I hooked up the 7 pin to the truck (which recognized the trailer), and ran through the lights/turn signal/brake lights process (can't recall what that process is called) and all lights worked and message indicated no issues.

However, the manual brake controller does not activate the trailer brakes, nor does applying the truck brake pedal.

So, a couple questions:

- Don't really understand the a/m check process. Does it only show the wiring to the various lights is working? In other words, this does not test the full brake circuit?
- if that is correct, no brakes then suggests there is an issue somewhere after the 7 pin cable?
- And if there is an issue at one of the brakes (ie loose wire), will that affect all brakes?

Thanks in advance,

Marv

[djsamuel]

marpel wrote:
Resurrecting this thread.

As I have been tied up looking after my grand-daughter, have been unable to work on the trailer until today. With old 7 pin cable and new one which I replaced today, the lights etc work, but none of the brakes operate (tandem axle).

I hooked up a brand new battery and pulled the breakaway switch. The brakes did not activate at any wheel.

I have checked the wiring at the front of the trailer and was only able to go under the trailer and do a visual on the brake wiring to all wheels, and everything looked OK (I know this is not definitive).

So, if the brakes are wired in parallel, which it appears they are, and if all brakes are inoperative, does this mean the issue is in the main cable somewhere prior to the first wheel connection? Just trying to get some advice on exactly where I should concentrate on looking.

Unfortunately, I am still doing babysitting duties so my time is limited to work on this. And the best part,I only have until this next weekend to figure this out.

Thanks in advance for any help,

Marv

Not trying to state the obvious, but you don't have a separate battery for the breakaway system do you? My trailer had that and when I tested the breakaway switch it didn't work, which is how I discovered the separate battery (which was dead). I've since wired the system to the house battery.

Just trying to help you avoid a mistake I made. 🙂

[StirCrazy]

you said it worked when you manualy applied the conrtoler, so then there shouldnt be a wiring issue at all, either your gain is turned down or its just not applying as you are stopped. when I have to do a tug test on my 5th wheel it doesnt appy untill I have rolled a little bit, has to detect motion. best way is to turn the gain to max, then go drive around the block at a deicent speed and then apply the brakes and see if it slows you down.

[Sjm9911]

Disconect the feed wire fron the brakes, put a meter on it and test it for voltage. Only way to know for sure.

[JIMNLIN]

Something else to check.....You can get 12v at the magnets with just a couple of strands of the brake wire. However it take the whole stranded wire to get proper amps to the brakes.
When buying new or a used rv/work trailer I always run a amp check at the magnets.
I've found those clam shell wire connectors over a short time can loose enough connection to limit amps to the brake....but still get 12v.

[marpel]

Resurrecting this thread.

As I have been tied up looking after my grand-daughter, have been unable to work on the trailer until today. With old 7 pin cable and new one which I replaced today, the lights etc work, but none of the brakes operate (tandem axle).

I hooked up a brand new battery and pulled the breakaway switch. The brakes did not activate at any wheel.

I have checked the wiring at the front of the trailer and was only able to go under the trailer and do a visual on the brake wiring to all wheels, and everything looked OK (I know this is not definitive).

So, if the brakes are wired in parallel, which it appears they are, and if all brakes are inoperative, does this mean the issue is in the main cable somewhere prior to the first wheel connection? Just trying to get some advice on exactly where I should concentrate on looking.

Unfortunately, I am still doing babysitting duties so my time is limited to work on this. And the best part,I only have until this next weekend to figure this out.

Thanks in advance for any help,

Marv

[marpel]

Grit dog,

Yes, the brakes worked fine previously, although with another truck. Due to circumstance, the trailer has sat for a number of months (bit over one year). And I have been able to confirm the current truck's trailer brake system does work (with another trailer).

Marv

[Grit_dog]

joebedford wrote:
Just to throw a contrarian post into the mix, on my truck 2011 Chev, the pressure sensor on the master cylinder failed and the brake controller (factory) would not activate the trailer brakes in auto or manual. Brilliant design - I had to haul trailer to get repaired without any trailer brakes. SCARY. They had no reason to disable the manual control.

That’s not contrarian. That is great info, as it’s not a typical cause of no trailer brakes.

[jkwilson]

Gdetrailer wrote:

jkwilson wrote:

Gdetrailer wrote:

jkwilson wrote:
How do you know the controller isn’t activating the brakes? Did you use a compass or listen for the hum at the wheels?

DC does not "hum", "buzz", "sing" or play any tune, you will not hear a thing.

Newer brake controllers while they do employ PWM to control the braking output operates at a very reduced output when you are sitting still. Even the manual lever output is reduced and does not apply full braking voltage when sitting still.

Even on older brake controllers, I never had any luck getting a compass to give a decent repeatable indication. There is a huge chunk of iron (drum) between the magnet and your compass. That drum absorbs and redirects a lot of the magnetic fields generated by the electro magnet and by the time it gets to your compass is very, very weak.

What I have found as 100% reliable way to trouble shoot is to jack up one side at a time and roll the wheels by hand and pull the break away pin. Wheels must stop as soon as the pin is pulled.

The breakaway system is supposed to apply full battery voltage from the trailer battery to the trailer brake magnets, if the breakaway system isn't working, then very good chance your truck system isn't going to make the brakes work either (IE trailer wiring problem)..

Put pin back in and you should now be able to roll the wheels by hand again. If they don't stop, then you need to access the wires behind each backing plate and verify that you have or don't have voltage with the breakaway pin pulled (note, the magnets are not going to melt either as per another Internet myth).

No voltage at backing plate then you have a break before the axles.

Voltage at the backing plate then you need to check the mechanicals behind the drum.

If you lift in the correct place, you can lift both wheels on the same side at a time.

Turn your flashers on with brake gain high. You’ll hear the magnets.

I have a 2013, 2019 and 2020 F250s, that does not happen.

Your flashers have zero to do with the IBC brake controller on Fords, you can turn up the gain to the max on the Ford IBC and while you are sitting still the controller will reduce the output even using the manual control. The flashers will not override the brake controller. The reason for that is when you are still, there is zero reason to apply full braking voltage.

Perhaps maybe if you turned on your windshield wipers and hummed "I love a rainy night" perhaps the brakes might hum with you?

Ford IBC folds back the braking output according to speed and that includes the use of the manual over ride.

It is done for your safety so you do not accidentally over apply electric brakes manually while driving at low speeds.

DC does not make a sound and even with the newer IBC controllers which use PWM to control the output any noise possibly made will be "solo" (so low you can't hear it).. The PWM is done typically at a high frequency which will be above human hearing range (young adult hearing range tops out at 20Khz, PWM typically will be above 20Khz).

Trailer brake magnets make a very distinctive sound when the brakes are applied. You are 100% wrong. It’s loud enough to hear it standing near a parked trailer. If you’d care to bet on it, I’d be in for any amount you want to lose.

[Gdetrailer]

jkwilson wrote:

Gdetrailer wrote:

jkwilson wrote:
How do you know the controller isn’t activating the brakes? Did you use a compass or listen for the hum at the wheels?

DC does not "hum", "buzz", "sing" or play any tune, you will not hear a thing.

Newer brake controllers while they do employ PWM to control the braking output operates at a very reduced output when you are sitting still. Even the manual lever output is reduced and does not apply full braking voltage when sitting still.

Even on older brake controllers, I never had any luck getting a compass to give a decent repeatable indication. There is a huge chunk of iron (drum) between the magnet and your compass. That drum absorbs and redirects a lot of the magnetic fields generated by the electro magnet and by the time it gets to your compass is very, very weak.

What I have found as 100% reliable way to trouble shoot is to jack up one side at a time and roll the wheels by hand and pull the break away pin. Wheels must stop as soon as the pin is pulled.

The breakaway system is supposed to apply full battery voltage from the trailer battery to the trailer brake magnets, if the breakaway system isn't working, then very good chance your truck system isn't going to make the brakes work either (IE trailer wiring problem)..

Put pin back in and you should now be able to roll the wheels by hand again. If they don't stop, then you need to access the wires behind each backing plate and verify that you have or don't have voltage with the breakaway pin pulled (note, the magnets are not going to melt either as per another Internet myth).

No voltage at backing plate then you have a break before the axles.

Voltage at the backing plate then you need to check the mechanicals behind the drum.

If you lift in the correct place, you can lift both wheels on the same side at a time.

Turn your flashers on with brake gain high. You’ll hear the magnets.

I have a 2013, 2019 and 2020 F250s, that does not happen.

Your flashers have zero to do with the IBC brake controller on Fords, you can turn up the gain to the max on the Ford IBC and while you are sitting still the controller will reduce the output even using the manual control. The flashers will not override the brake controller. The reason for that is when you are still, there is zero reason to apply full braking voltage.

Perhaps maybe if you turned on your windshield wipers and hummed "I love a rainy night" perhaps the brakes might hum with you?

Ford IBC folds back the braking output according to speed and that includes the use of the manual over ride.

It is done for your safety so you do not accidentally over apply electric brakes manually while driving at low speeds.

DC does not make a sound and even with the newer IBC controllers which use PWM to control the output any noise possibly made will be "solo" (so low you can't hear it).. The PWM is done typically at a high frequency which will be above human hearing range (young adult hearing range tops out at 20Khz, PWM typically will be above 20Khz).

[jkwilson]

Gdetrailer wrote:

jkwilson wrote:
How do you know the controller isn’t activating the brakes? Did you use a compass or listen for the hum at the wheels?

DC does not "hum", "buzz", "sing" or play any tune, you will not hear a thing.

Newer brake controllers while they do employ PWM to control the braking output operates at a very reduced output when you are sitting still. Even the manual lever output is reduced and does not apply full braking voltage when sitting still.

Even on older brake controllers, I never had any luck getting a compass to give a decent repeatable indication. There is a huge chunk of iron (drum) between the magnet and your compass. That drum absorbs and redirects a lot of the magnetic fields generated by the electro magnet and by the time it gets to your compass is very, very weak.

What I have found as 100% reliable way to trouble shoot is to jack up one side at a time and roll the wheels by hand and pull the break away pin. Wheels must stop as soon as the pin is pulled.

The breakaway system is supposed to apply full battery voltage from the trailer battery to the trailer brake magnets, if the breakaway system isn't working, then very good chance your truck system isn't going to make the brakes work either (IE trailer wiring problem)..

Put pin back in and you should now be able to roll the wheels by hand again. If they don't stop, then you need to access the wires behind each backing plate and verify that you have or don't have voltage with the breakaway pin pulled (note, the magnets are not going to melt either as per another Internet myth).

No voltage at backing plate then you have a break before the axles.

Voltage at the backing plate then you need to check the mechanicals behind the drum.

If you lift in the correct place, you can lift both wheels on the same side at a time.

Turn your flashers on with brake gain high. You’ll hear the magnets.

[Grit_dog]

You didn’t say if the brakes worked previously recently with another truck or ?

[marpel]

Thanks very much for the continued replies and advice.

I just went through jacking the trailer and inspecting/regreasing etc, each wheel. I am comfortable with that stuff, but didn't consider checking the electricals. It was only when I hooked up the trailer to the truck (brand new '22), that I discovered no brakes. And as electricals is not my strong suit, I sought advice from the forum. And I am learning a lot, so thanks for that.

I think next step will be, as others have advised, activate the breakaway system. Then go from there.

Having said that, My grand-daughter is about to arrive for a couple week visit and she demands my full attention, so the brakes will have to wait a bit. As we are driving her back home (BC to Denver) with the trailer, I will have to figure this stuff out prior to heading out.

Thanks again for all your help,

Marv

[Grit_dog]

Gdetrailer wrote:

Grit dog wrote:
To see if the trailer side is good, jump 12v to trailer side pin for the brakes. Should lock them up tight.
Your truck sounds fairly new. Is there a readout for trailer brake gain?

Don't have to "jump" anything, just pull the emergency breakaway pin then pull forward.. Break away system overrides the vehicles system (vehicle brake controller, wire and socket).

All wheels must lock and hold when break away system is activated.

Break away switch supplies full 12V from the trailers' on board battery.

If break away system does not lock any wheels then you must troubleshoot and diagnose the TRAILER electrical system and the mechanical part of the brakes behind the drums.

If break away locks all the wheels then consider changing the 7 pin connector and cable.

You have a 99% chance the trouble is not the vehicles fault but folks love to blame the vehicle for everything.. :R

Great tutorial but does nothin to diagnose a short in the trailer plug or pig tail, upstream of the breakaway system.

[joebedford]

Just to throw a contrarian post into the mix, on my truck 2011 Chev, the pressure sensor on the master cylinder failed and the brake controller (factory) would not activate the trailer brakes in auto or manual. Brilliant design - I had to haul trailer to get repaired without any trailer brakes. SCARY. They had no reason to disable the manual control.