Attention all electric brake scientists:

[bangzoom]

I've got a new situation here. TV: 2011 F250 WITH FACTORY BRAKE CONTROLLER. TRAILER: 2007 25' SAFARI SS SE. HITCH: PRO PRIDE WITH JACKS SET AT 6.75". TRAILER LOADED WITH USUAL SUMMER STUFF, FULL FRESH, EMPTY GREY AND BLACK. TRUCK LOADED WITH USUAL SUMMER STUFF. BRAKE CONTROLLER SET AT 6.5, JUST BELOW WHEEL LOCK UP. WHILE DRIVING IN HEAVY RAIN, I BRAKED TO SLOW DOWN FOR CONDITIONS AND BOTH THE NOSE OF THE TRUCK AND REAR OF THE TRAILER PITCHED TO THE RIGHT ( THE JACK KNIFE POSITION ). LATER ON, UNDER DRY CONDITIONS, THIS CONTINUED TO HAPPEN IN 90% OF BRAKE APPLICATIONS. OCCASIONALLY, IT WOULD TRACK STRAIGHT. YESTERDAY AT HOME, I WENT OUT FOR A TEST RUN TO TRY AND ISOLATE THE PROBLEM: TRUCK EMPTY, CONTROLLER SET AT 5.5, TRAILER EMPTY EXCEPT FOR FULL FRESH TANK, PRO PRIDE ADJUSTED FOR LIGHTER LOAD. AT 35 MPH, JUST A SLIGHT VEER TO RIGHT. AT 60 MPH, IT WAS BACK TO THE JACK KNIFE POSITION. AT ANY SPEED USING THE MANUAL BRAKE CONTROLLER ALONE, NO SWAY. AT ANY SPEED WITHOUT THE TRAILER, THE TRUCK TRACKED STRAIGHT WITH BRAKES APPLIED. GIVEN THE SYMPTOMS, I FIGURED I HAD POOR BRAKING ON THE RIGHT SIDE OF THE TRAILER. PULLED THE RIGHT FRONT AND RIGHT REAR DRUMS: NO GREASE EXCEPT WHERE IT WAS SUPPOSED TO BE, SHOES IN GOOD SHAPE, MAGNETS ARE 2 YEARS OLD AND IN GOOD SHAPE. DRUMS WERE TURNED WHEN MAGNETS REPLACED. WITH CONTROLLER SET TO 10, 10 VOLTS AT BOTH WHEELS, RIGHT FRONT MAGNET AT 3 AMPS, RIGHT REAR MAGNET AT 1.3 AMPS. IS THIS THE CULPRIT? I THOUGHT THAT AMPERAGE WAS PROPORTIONAL TO VOLTAGE. ANY THOUGHTS OR SUGGESTIONS WOULD BE APPRECIATED.

[HowieE]

It is as long a resistance remains the same.

I would swap the magnets and test again. If the problem moves with the magnets the magnet is the problem. If the problem remains at the original position there is a resistance in the wiring to that magnet.

[Protagonist]

Playing Devil's Advocate, there is another possibility. Don't overlook the mechanical side of things. You say that drums and shoes look fine, but are they all adjusted the same? One brake could be grabbing harder simply because the brake shoe has less distance to travel when the brakes are applied. A feeler gauge between the brake shoes and the drums will tell the tale.

[bangzoom]

Sorry i forgot to mention that. Did not test with a feeler gauge but all brakes are adjusted equally to the best of my ability. All tire pressures also equal.

[J. Morgan]

If the combination veers to the right, it seems to me that it is probably the LEFT side brakes that are not working. ?

[J. Morgan]

You can get on the dirt move slowly and fully apply the trailer brakes, the skid marks will tell you which brakes are working and which are not.

My guess is that the brakes on the left are out of adjustment and/or there is an electrical issue on the left side making the left brakes inoperable.

Maybe the left ground wire is broken?

[TG Twinkie]

I think the problem is. Not with too much brake in the trailer, but not enough. When a hitched rig jackknifes it tells me that the trailer is pushing the TV. Either because of slow response of the brake controller or maladjusted brakes on the TV. Because the trailer is pushing the TV into the jackknife position.
I would look for wiring problems on the trailer first. If there are bad splices in the wire connections at the backplate. Also check to make sure all brakes are working.
If when you apply the electric brakes manually, you can feel the trailer holding back the TV. It indicates at least some of the brakes are working. Perhaps not enough.
The trailer brakes should hold the trailer back as compared to the TV brakes. Always giving a slight rearward pull over the TV brakes. It's what keeps the rig straight.

[bangzoom]

You may be right. I just figured the good side was trying to center itself behind the trailer pivot point at the hitch, thus pushing the rear of the trailer to the right. Anyway, i just wanted to post the problem before i got any greasier.

[J. Morgan]

As a rule, when brakes on ones side are not working, the vehicle will track toward the side that is working when stopping hard.

Your ProPride throws a new variable in here, but only to the degree that the combination will move as a unit toward the good side.

I think you are going to find that the brakes on the right are hitting much harder than those on the left.

When the brakes on the right apply, the inertia on the left side of the vehicle will continue to act pushing the left side forward whole the right side tends to pivot on the right side tires, therefore the vehicle will move sharply to the right.

[HowieE]

You have defined the problem in the fact that you have one magnet that is not working on the right side of the trailer. That would cause the trailer to force the rear of the TV to the left and thus the front to the right. Find out whu you do not have that one magnet working as noted above and go from there.

[bangzoom]

Will swap magnets as suggested

[Chipster]

Whatever the cause, isn't the ProPride supposed to keep the total rig straight ? I am surprised to hear this story.
chip

[jkcru]

Don't over look the hitch. Make sure it is properly centered and all bolts secure.

[J. Morgan]

I have worked fairly extensively with trailer brakes for 25 years, from what I am able to extract from the master post, I am 99% sure the problem is going to be with the left side trailer brakes not working or barely working.

The ProPride makes the issue slightly different, but based on the information available to me I will stick with my diagnosis.

If possible the test on a dirt lot will tell you a lot.

[bangzoom]

Chipster: Problem was with the hitch. Not broken--just loose bolts. My fault.

[bangzoom]

Jkcru: It was the hitch. Not broken--just loose bolts. My fault. Thanks again.

[J. Morgan]

Good call on the hitch!