Bit of a puzzle going on with electric brakes

[noteven]

I hooked up the Big Toyhauler the other day. All lights and signals function correctly. But - no brakes. Hmmm.... 

I am a bit of a dummy when it comes to things electrical. 

Here is what I know so far, with Hayes air/electric controller:

Jump 12v direct to the brake terminal on the trailer cord, brakes come on.  Verified with one wheel off the ground and listening for magnets humming. 

Test truck 7 way plug.  12v is present on the brake connection in the plug at all times. When trailer is plugged in it's brakes do not come on. 

Cleaned connections in truck and trailer plugs. 

13.5v at battery terminals on truck at slow idle.

12.6v at the blue wire coming out of brake controller at all times. 

12.6v at black wire coming in to brake controller from truck. 

0v at red brake switch signal wire from truck.  12v at this wire when truck brakes are actuated. Trailer brake blue wire volts do not change, stay at 12,  brakes to not come on. 

Disconnect Hayes, connect a simple Tekonsha controller. 

All readings etc. identical to above.

Tomorrow I connect a 3rd known to be good controller from another truck. 

No fuses blown. 

Any and all ideas welcome. 

Thanks

 

[Wrknrvr]

What are you pulling the toy hauler with. Pickup or MDT.

Some late model Chevy/ GMC trucks have a electric thing on the rear of the chassis. If it is not working properly it can cause problems.

 

Let’s start with this first,   Vern

[GlennWest]

12v always coming from tow vehicle? That can't be right. Brakes would stay on. I would tow vehicle receptacle bad.

[Darryl&Rita]

Brakes aren't activated by voltage, it takes current to drive them. Each brake should run about 3 amps. If you insert your meter leads into the wiring on each axle, set to DC AMPS, each axle should read 6ish amps. Most meters will handle 10 amps, so don't get rushed and try all the axles at once. I'd start with the rear axle, and work my way forward. If you don't get any current readings on the trailer axles, it's time to look at the splice box at the hitch, the connections at the bumper, then the tow vehicle wiring. Work your way forward.

[noteven]

9 hours ago, Wrknrvr said:

What are you pulling the toy hauler with. Pickup or MDT.

My wee Kenworth - Hayes air/electric controller

Some late model Chevy/ GMC trucks have a electric thing on the rear of the chassis. If it is not working properly it can cause problems.

 

Let’s start with this first,   Vern

 

9 hours ago, GlennWest said:

12v always coming from tow vehicle? That can't be right. Brakes would stay on. I would tow vehicle receptacle bad.

I suspect it is a low current "leak" - see Darryl's remarks below

 

7 minutes ago, Darryl&Rita said:

Brakes aren't activated by voltage, it takes current to drive them. Each brake should run about 3 amps. If you insert your meter leads into the wiring on each axle, set to DC AMPS, each axle should read 6ish amps. Most meters will handle 10 amps, so don't get rushed and try all the axles at once. I'd start with the rear axle, and work my way forward. If you don't get any current readings on the trailer axles, it's time to look at the splice box at the hitch, the connections at the bumper, then the tow vehicle wiring. Work your way forward.

The problem appears to be on the truck.  Another person (who does heavy haul etc) used it to move their Big Toyhauler. He called me "how do I set this brake controller?" I let him know ok bye.  It came back and got put away for the winter. It got a couple bob tail exercise trips last summer. I hooks on the trailer this fall and no brakes. I calls person above "oh ya... I forgot to let you know there were still no brakes..." 

Anyway I put power direct to the trailer circuit at the plug in the shop and brakes come on. I did not measure as above thank you for that info. 

Today I am going to check truck vs a known good brake trailer, call Hayes tech support etc. 

[Kirk W]

10 hours ago, noteven said:

Test truck 7 way plug.  12v is present on the brake connection in the plug at all times. When trailer is plugged in it's brakes do not come on. 

                

              

Pin #2 should not have 12V at all times but only when the trailer brake control is apply trailer brakes. If all lights are off  and truck engine is running, only pin #4 should read 12V when measured to ground, or the truck frame. It would be wise to shut everything off and then measure the resistance from pin #1 to the truck frame looking for 0 ohms or very close to that. The same action on the trailer plug to the trailer frame would also be a good idea. 

Have you checked to see if the trailer's brake-away switch will apply the trailer brakes? If the trailer is not the problem, that should happen without any tow vehicle connected. 

 

[Wrknrvr]

  Now I am thinking I better plug our truck in to the fifthwheel today. We have been sitting from the beginning of the covid thing, so I better check today. I did pull the wheels for greasing and check things. All look good, but better test the whole braking system.

  We were leaving today but weather has postponed our travels. And the Jeep is still drivable. As in it is supposed to be loaded on the truck by now. Maybe today or tomorrow.

  Still making toys in the machine shop before we leave. The wife would not let me take the lathe along for the winter.

 As Darryl says start at the back of the truck, on the easily accessible junctions. Then maybe the easiest accessible junctions at the cab area.

 

 I will try and keep the snow off I-15 for you. 

 

   Vern

 

 

[dennisvr]

Does your controller have a lever on it so your can actuate the trailer brakes without the truck brakes?  If so I would move the lever and check for voltage at the plug.  If you get voltage when the lever is moved, then the problem would be between your truck brake system (elec or air) and controller or the controller itself.  

 

[Wrknrvr]

   Do you have brakes yet. Or is the snow too deep to work in.

 

  Just curious,    Vern

[beemergary]

You should have 12v at 2 locations when the brakes are activated. Is that 12v just your 12v hot wire?

[noteven]

2 hours ago, Wrknrvr said:

   Do you have brakes yet. Or is the snow too deep to work in.

 

  Just curious,    Vern

Been off the project for a couple days - it has been sunny and nicely above freezing so helped with a couple outside jobs. 

Heated shop to work in 😎 once I get back to it.

[noteven]

2 hours ago, beemergary said:

You should have 12v at 2 locations when the brakes are activated. Is that 12v just your 12v hot wire?

The controller indicator light is on with no trailer connected and off with trailer connected. It then comes on when brakes are applied. This is correct as per Hayes manual.

The controller has 12v from truck on black wire, 12v from truck on red wire when truck brakes are activated. White/ground has continuity to truck at the 7 way plug and the controller connection. 

The problems I am chasing are: brake circuit (blue wire) is showing 12v (with key on) whether the controller is activated or not, but the brakes are not activating on the trailer.

The brakes activate on the trailer when 12v / ground are supplied direct to the cord. 

I have been doing other things for a couple days. 

Thanks

 

[GlennWest]

sounds like lost ground. Need a clamp on amp meter. Yu would not supply ground with it.

[Wrknrvr]

  Some times I think very slowly. Really slowww. Some controllers have a pendulum to activate the system. So that could be one problem with your diagnosis. Vehicle has to be slowing down to activate the controller.

  Since it has been awhile since I have worked on brakes it takes awhile to remember stuff. I do believe there should only be about 6volts dc on full activation from the controller. If the emergency cord is pulled it will supply for battery voltage. Like 12vdc and will lock the brakes. 

  So I will think that crude brake controllers are just a rheostat? Not really sure about that. Adjust them to suit and it applies that given voltage. The pendulum may regulate the voltage applied in more modern controllers.

  So after that thinking I would check all connections in the wiring. Now one thing could be that someone used the frame for a ground. Check all connections.      Maybe a regular 12vdc test tight to see what happens. If you use a meter or led light it may give a false indication.

  Also some modern electronics have voltage in the system all the time. Not sure about your controller. It will not pass amperage. But makes electric stuff last longer. If you experience the voltage in the system on something that you think it is not supposed to be there it is dam confusing..

 

  on Aquahot heating systems use the the switching of power for pumps on the ground side of a motor.   What the heck, the motor has power all the time. Dam confusing until you understand it. In reality I think electronics stuff works better and longer with the ground switched.

 

  Onetime years ago I was working on a hydraulic leveling system.   What the he—. I finally figured out that the motor was switched on the ground side. The tech service person explained it to me. Then the system was easy to diagnose. But before he explained it I was really mad to say the least. 

 

     Hope this helps,   Vern

[Kirk W]

Vern has given some very good advice. Modern brake controls have some type  of decelerometer built into them. Cheap ones were just a pendulum but better ones use an electronic device. They cause the amount of power applied to the brakes of the trailer to decrease as you slow and most will stop completely when sitting still with the brake applied. 

Another thing to realize is that if you are taking measurements without the trailer connected then you are working into an open circuit. When you do that you will always read the full source voltage applied. Only when current is flowing can you read the actual voltage that is applied to each part of a circuit. A simple volt/ohm meter will only give you an accurate reading for what your brake controller applies to the trailer brakes when the brakes are applied and that will vary depending upon the deceleration rate at the moment. To accurately check all functions of a modern brake control system, better shops use a device like this one from Norther Tool.    

                

The best way to check the trailer brakes for full application is to pull the brake-away switch. When you do that the full voltage from the trailer battery is applied to the brake solenoids and stays there until the plug is put back into the switch.

As Vern said, early brake controls were just a rheostat that was mechanically linked to the brake pedal and moved with the pedal but modern controls are not tied to the pedal at all but apply when they get a signal from the tow vehicle brake and then operate by their own electronic system. The manual apply brake switch should apply power even sitting still but you will still need to have the trailer connected or you will be reading source voltage and not the actual voltage applied. 

[Kirk W]

12 hours ago, noteven said:

The brakes activate on the trailer when 12v / ground are supplied direct to the cord. 

That does pretty much the same thing as it does to pull the brake-away so if the brakes apply fully when you do that, it means that the trailer brakes are OK.

[noteven]

Thanks for the replies. My truck went on a couple short flat land trips without me last summer with electric brake trailer not mine. The user confirmed his trailer brakes were not working last trip “with that truck you don’t notice on dry roads” Forgot to mention it….

The control is a Hayes air/electric proportional contol. It responds to the air brake application pressure of the truck. I got bizzy with some stuff and haven’t sat down to contact their support line to see if I have equipment to test it.

Kirk I called 2 shops about that brake control tester - um, ya, we don’t have one of those…

Couple more places to chase after the week end.

 

[Darryl&Rita]

1 hour ago, noteven said:

I called 2 shops about that brake control tester - um, ya, we don’t have one of those…

Build one. Plastic tool box, ammeter rated for 20 amps DC, rotary selector switch, and headlamps for the load. Put a trailer cord end on a piece of extension cord, feed into the box. Through the ammeter, to the selector switch, then to the loads. If you use the right wattage bulbs, each one can simulate an axle. Select one axle, two, or trip. Watch the ammeter needle, each "axle" should be roughly 6 amps. If you build it with a female connector and a power supply, you can also use it for testing the trailer side.

[noteven]

Fixed it!

Got back to the issue late pm today. 

Wiggling of wires while checking continuity and whaddya know - 

Intermittent broken ground between the controller and the batteries in the truck wires. 

Thanks everyone for replies and ideas.