Help with my brakes!! - Page 2

dkwin1 · 07-10-2012, 09:40 AM

Yes your probably right. Never thought of that.

dkwin1 · 07-10-2012, 11:29 AM

OK. I brought it to a local RV center here close to home and they were nice enough to test the output of the 7 pin with a special part to confirm I am getting voltage out when the brake is applied. When I had the gain on 6.0 the light was fairly dim but when we increased it to 8.0-9.0 the light was where it was supposed to be. The guy told me that the magnets are probably getting worn but I should be OK.

He did tell me that if I had the means to jack up the 5th wheel (which I never did and really don't want to do as I have no idea how to jack this thing up) I could jack it up until the wheels are off the ground and then have someone apply the brake and see if the wheel spins.

Any tips/suggestions about jacking this thing up (I have a 3 ton floor jack). This really scares me but I want to do it for my own piece of mind. Any tips are greatly appreciated.

OldCoot · 07-10-2012, 11:38 AM

Quote:

Originally Posted by dkwin1

...Any tips/suggestions about jacking this thing up (I have a 3 ton floor jack). This really scares me but I want to do it for my own piece of mind. Any tips are greatly appreciated.

Cut a 4 x 4 to fit between the axles and jack on the 4x4. DO NOT jack on the axles!

dkwin1 · 07-10-2012, 12:00 PM

So jack on the frame. Correct.

OldCoot · 07-10-2012, 01:06 PM

Quote:

Originally Posted by dkwin1

So jack on the frame. Correct.

Only between the axles. The frame itself will not take the load of one side of the trailer.

Between the axles there are steel tubes and the actual frame itself is a fabricated I beam made of thin material.

dkwin1 · 07-10-2012, 03:25 PM

I called the dealer that I actually bought the unit from and the service manager said that the led should be bright as h*ll even at a gain of 3.0. He said from the start that it is the truck not outputting enough voltage. While I did not believe that I am starting to. I will be dropping the truck off at Ford in the next couple of days and let them deal with it. Hopefully it is in the truck as it is still under warranty.

I am not going to jack the 5th wheel up until I get the truck back from Ford and see if they solved the problem.

FOI- you mention steel tubes and the frame is made of fabricated I-beam. are you saying to jack on the tubes. Sorry for the stupid questions but I am new to this and really don't want to screw up here. Thanks.

Dave_Monica · 07-10-2012, 05:51 PM

Quote:

Originally Posted by dkwin1

He did tell me that if I had the means to jack up the 5th wheel (which I never did and really don't want to do as I have no idea how to jack this thing up) I could jack it up until the wheels are off the ground and then have someone apply the brake and see if the wheel spins.

I don't see the point of these recommendation by the dealer. You've already established this on your road test and trouble shooting.

I do see the opportunity to check the adjustment of the brakes if you were to jack it up...only need to do one side at a time. The wheels should be free to turn but you should hear the brake shoes contacting the drums.

Dave

OldCoot · 07-10-2012, 06:07 PM

[QUOTE=dkwin1;220788]...you mention steel tubes and the frame is made of fabricated I-beam. are you saying to jack on the tubes. Sorry for the stupid questions but I am new to this and really don't want to screw up here. Thanks.[/QUOTE

There are no stupid questions especially yours. If you place the 4x4 BETWEEN the axles it should be next to a formed angle that is below a 2x2 steel tube which is below a 2 x 4 steel tube. The frame is just not strong enought to carry the pressure of a jack. The steel tubing spreads the load out along about a 4' length of the frame.

dkwin1 · 07-11-2012, 01:36 PM

I other question that hopefully someone knows. I wanted to take some voltage reading on the brake pin myself but someone told me that you have to have a special 7 pin plug with flying leads in order to fake out the truck in thinking there is a trailer hooked up. You cannot simply put a meter on the brake pin as there will be no voltage there because the truck thinks there is nothing hooked up. Is this true?

dkwin1 · 07-11-2012, 01:36 PM

Old hoot. Thanks for your feedback. Boy you sure do get out.

dkwin1 · 07-11-2012, 01:42 PM

Oops. Meant old coot. Sorry.

jimh · 07-11-2012, 02:15 PM

Quote:

Originally Posted by dkwin1

I other question that hopefully someone knows. I wanted to take some voltage reading on the brake pin myself but someone told me that you have to have a special 7 pin plug with flying leads in order to fake out the truck in thinking there is a trailer hooked up. You cannot simply put a meter on the brake pin as there will be no voltage there because the truck thinks there is nothing hooked up. Is this true?

this is strictly a guess: i would think the voltage shown with a meter would be higher that it would be if under a load. a good voltmeter will offer little to almost no load.

**Herk7769** · 07-11-2012, 02:21 PM

Can't speak to all controller types, but my GMC integral controller uses the completed circuit through the brake magnet to ground to determine if the camper is "connected."

As such there is "some" voltage on the brake circuit pin all the time. Full voltage should only be there if the tow vehicle's brake is pressed all the way down or the manual override is on full.

dkwin1 · 07-11-2012, 02:38 PM

Thanks to everyone who has responded to my problem. Boy am I learning a lot on this forum.

1 more question. I drive with the gain at 6.5. When you slide the slide on the controller does it output max voltage to the brakes or what does it do. I read on here that you should adjust your gain to the point that you are not locking up the tires when you slide your controller. I am trying to understand what the slide does on the controller.

**Herk7769** · 07-11-2012, 02:52 PM

The manual "slider" applies a variable voltage to the trailer brakes.

The more you squeeze the toggles together the higher the voltage applied to the brake magnets.

The higher the voltage at the brake magnets; the stronger the magnets are at grabbing the brake hub.

The stronger the brake magnets the more pressure is applied by a lever that is attached to them to the brake shoes; that then lock to the TURNING hub.

NOTE: if the drum is NOT turning you have NO BRAKES even squeezing it full.
The magnet will NOT move like graphic; it will just grab the hub and not move.

The hub has to turn in order to jam the brake shoe lining into the hub.

The brake controller should be adjusted such that there is no noticeable pull or push on the truck when braking.

If, when you brake the truck, the trailer seems to "push" you; the controller is set too "LIGHT". If you feel it yank on the truck (or pop the 5th wheel hitch) the controller is set too "heavy."

dkwin1 · 07-11-2012, 02:57 PM

Herk,

So are you saying that if you only slide the toggles 1/2 way your only putting 1/2 max voltage to the brakes.

What I read here and I am trying to find it is that you should adjust your gain to the point that you are not locking up your brakes when you fully squeeze the toggle. However it sounds from you that this would be impossible since when you squeeze the toggle completely together it will lock the tires out and certainly lock them up. I am just trying to understand what this toggle does. Does it completely lock up the tires when completely squeezed??

jimh · 07-11-2012, 03:33 PM

adjust as herk said.

what goes on in the controller when u apply the brakes, the brake light signal goes to the controller. the controller will deliver a voltage proportional to how quick the viehicle is being stopped (with the amt of gain u have adjusted)...ie there is a pendulum inside the controller that swings according to how hard the vehicle is stopping. on the external controllers, u have to adjust a lever to vertical after installing the controller. The truck manufacturer has already done this step.

they may have a more different way of detecting the rate of deceleration than the pendulum now days, but that is basically what is going on.

the gain determines the amt of voltage the manual lever is allowed to put on the brakes. haven't noticed if it is also controlled by how much u push the lever. i'm thinking it does.

**Herk7769** · 07-11-2012, 03:54 PM

I can only go by what I know and understand about MY controller.

The variable gain that you SET into the controller determines the max voltage that can be applied with full braking. It should be set BASED ON THE WEIGHT of your camper.

When set correctly you should be able to stop the camper at low speeds (about 20 MPH) WITHOUT skidding the trailer's wheels YET not feel the camper pushing you. Take the camper loaded for camping to a large parking lot (we have a big K-Mart where I set mine) and play with the settings till it feels right.

Remember skidding the tires means you have NO trailer brake action; not max brakes. Skidding tires quickly develop a layer of melted rubber that acts like oil under the wheels.

The manual slider bypasses the controller and applies maximum voltage unaffected by the gain setting to your camper's magnets and can easily lock them up at LOW SPEEDS. (Just try it - without the DW on board as she will not be pleased).

It is VERY difficult (maybe impossible) to lock up the camper's tires at speed. There is just too much inertia in the spinning hub for a magnetically applied brake shoe to do it.

Where the manual toggles earn their money is if you are in a violent sway or a loss of truck braking, you can apply the camper's brakes WITHOUT applying the truck's brake. This will straighten out the combination without worsening the sway emergency.

Again; this applies only to MY understanding of how the GMC controller functions.

jimh · 07-11-2012, 04:15 PM

this is for several post back when it was asked if u could test the controller w nothing connected. u can't, if u check the voltage with nothing connected, u will find it to be 12 volts.

i'll have to check the manual lever operation the next time out...interesting question.

**Herk7769** · 07-11-2012, 05:50 PM

Trailer Brake Controller Reads NC, No Trailer Connected, With or Without a Trailer Connected | etrailer.com

Seems to indicate a ground needs to be made (through the magnets) and a power signal from the brake controller has to be sent (from the override or brake pedal press for significant signal to appear on the brake pin of the connector.

A Ground on the brake pin seems to be required for a "trailer connected" to be displayed on the controller. How it determines a ground is available is a mystery if no signal is there to measure it.

Perhaps a "comparator" circuit in the controller? Comparator - Wikipedia, the free encyclopedia

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