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Old 02-22-2009, 12:09 PM   #1
AnEyeForTexas
 
1962 26' Overlander
Lockhart , Texas
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Intermittent brake lockup

After driving a couple of hours (62 Overlander), my brakes start locking up intermittently. This drug me to a complete stop on the exit ramp between I10 and I35 which was pretty exciting.

I took it to the Airstream repair place, and they rewired everything because of a faulty ground, etc., but suggested that my "brake modulator" was probably at fault. So I took the truck to the mechanic who fixed the switch that activates the brake lights when you step on the pedal.

I finally got out of town only to have the same thing happen 125 miles or so down the road. Now the "brake activator" is going nuts, ramping up to full current at the slightest touch of the brakes and locking the tires. It's very hard to drive that way.

So, two questions. (1) what is the difference (if any) between a "brake activator," "brake controller," and/or "brake modulator?" Are we talking about the little box mounted under the dash? (2) Anyone else experienced similar problems? If so, what was the diagnosis?

I'm taking the truck to a Chevy dealer to have things checked. I'm thinking the controller box under the dash is squirrely, but I'd like to know about what I'm discussing with the mechanic tomorrow.

TIA
Gary
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Old 02-22-2009, 01:06 PM   #2
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Gary,
I am pretty sure all your terminology refers to the brake controller, the little box under your dash board. What type of controller do you have and have you followed the instructions to "calibrate" it and set what I would call the "gain" or "boost" on the unit??? I would also check all wiring connections to make sure they are secure and there is no shorting going on. Also units usually work best when they are parallel with the road surface.
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Old 02-22-2009, 02:32 PM   #3
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Most modern brake controllers (box under the dash) only know that the brakes have been pressed by way of the switch that activates the brake lights. The brake controller then determines the amount of current to apply based on the inertia detector built into the unit. If the unit is ramping the current up and down to the point that the brakes lock, the unit is most likely defective. A properly adjusted brake controller should not lock the brakes. A defective break-away switch on the trailer will.

What brand of brake controller do you have? Many of them will display the amount of current they are applying to the brakes when you step on the brake.
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Old 02-22-2009, 04:37 PM   #4
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We need to know more about what controller you are using.

So far I would say that neither of the so called problems that have been addressed could have been the problem. If you had a Faulty Ground you would have had No Brakes on the brake effected and reduced overall braking. If the Brake Switch was bad you would have had No Brakes.

Don't go to a Chevy Dealer as the only thing involved with your trailer brakes that they have any knowledge about is the Brake Switch and if you have brake lights on the car that is working.

My first suggestion would be to go through the controller calibration setup and make sure it is correct. If you have a grand daughter like mine who moves every switch or dial in sight she may have changed the calibration.

Can we assume that this random stopping only happens after you have touched the brakes or has it happened completely free of applying the brake just while you are driving?
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Old 02-22-2009, 04:55 PM   #5
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Well, thank heavens it's probably not rusted out brakes.

Gotta tell the story of Esmeralda, my old, beat-up VW (named after the butterfly-sensuality-prostitute metapher in Thomas Mann's Magic Mountain). Poor Esmeralda had more problems than you can shake a stick at, completely rusted out rear brakes among them. Not having the money to repair it all, I bought a hammer at the hardware store in Munich. And when Esmeralda started jerking (a sure sign that the rear brakes were seizing up), I'd just stop the car, get out, and pound on the drums a few times. Problem solved, on with the drive. Poor Esmeralda. I traded her for a nice used camera before I left Germany.


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Old 02-22-2009, 05:01 PM   #6
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Mine did the same thing,the actuator was bad,it would say 1.5 then ever once in a while it would smoke the tires,disconnected for the other 30 miles home.Replaced it with new controller,been fine for a few 1000 miles now. Dave
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Old 02-22-2009, 05:21 PM   #7
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You may want to carefully check the 7 pin plug. It can short out inside the male (trailer side) end. I had this happen on my boat trailer and it ruined all for disc brakes and calipers. I went through everything else before I found the plug. I ordered molded 7 pin plugs for the boat and the AS. Good luck.
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Old 02-23-2009, 08:51 AM   #8
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Let's see if I can answer all your questions. I have a Lock Tite Actuator II. The problem happens without my taking action of any sort. The connections and wiring have all been re-done and tested. I've been through the controller setup (such as it is). When this problem happens I cannot even turn everything down to 0 and go on.

I'm inclined to believe that it is the controller. I'm just trying to narrow the problem down to brakes or controller.

Thanks for the advise. I'll continue continuing on.

Gary
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Old 02-23-2009, 09:09 AM   #9
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Kelsey makes a small clip on amp meter for monitoring brake current. If you can get one of them clip it on the output line from the brake controller and when this happens see if there is current coming from the controller. Another way to check this is when the brakes lock disconnect the output wire from the controller and touch the 2 wires together checking for a spark. If you see a spark the controller is feeding current to the brakes and is most likely bad.

If you do either of these tests and do not see current coming from the control while the problem is present I would do a Phil suggested and check for a short in the plug or receptacle. These are very tight areas with the wires not well insulated between connections and if not installed with care and result in cross connections

An off the wall thought. Is it possible that the brake safety wire is so tight that it is being partially pulled out and setting the brakes wit the trailer batteries. Not sure I can see this happening and resetting itself but I have seen brakes locked by the safety switch.

What causes the problem to go away once it happens? Do you bake up the rig? Do you unwire anything? Or as mentioned do you hit anything?
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Old 02-23-2009, 10:38 AM   #10
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I would also check ..........

Have you checked the break away switch. Those switches are exposed to the elements.
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Old 02-24-2009, 10:02 AM   #11
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A repairman is coming today to install a new controller. Even if that is not the problem, it will be a better one than the mechanic in Lockhart installed. I will insist that this one have a switch or plug installed so that it can be disconnected without affecting the signal lights in case the controller is not the problem. I'll let you know the outcome.

Gary
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Old 02-24-2009, 12:25 PM   #12
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Quote:
Originally Posted by gnored View Post
I will insist that this one have a switch or plug installed so that it can be disconnected without affecting the signal lights in case the controller is not the problem. I'll let you know the outcome.
Gary
Gary I am sorry but I must say the installation of an Over Ride Switch is a very bad idea.

Besides being unsafe I am sure that if anything happened and your insurance company got wind of it they would walk away and may even through to the lions.

You still have not mentioned how you release the brakes once this happens. Does it just resolve itself or do you do something.
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Old 02-27-2009, 02:23 PM   #13
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Well I got the new controller (a Tenosha-something or other) and the problem pretty much went away. Brakes kicked in once on the way to Alpine.

Curious. If I stay under 55 the problem doesn't happen at all. What could speed have to do with it? What could hills have to do with it (it only happens when going uphill).

Aaarggh!

Gary
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Old 02-27-2009, 03:03 PM   #14
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Well if the brakes kicked in ONCE with the new controller the problem clearly was not the controller. That and the fact that you have to remain below 55 mph is another indication the problem is not yet solved.

I can only think of 3 sources of power for the brakes. You have addressed the controller and I have to assume that you could not have had 2 defective controller or that 2 installers had no idea of what they were doing. So for the other 2 sources.

As mentioned before the wiring in the receptacle is subject to shorting across connections do to the very close spacing between terminals. However a short in these components would tend to be constant and not subject to road vibration. However it is any area that I would clearly inspect just to get it out of the equation.

The third source of power to the brakes is the brake away switch. This switch is held open by the plunger that is connected to the wire cable leading to your TV. The easy way to test it would be to stick a pin into each of the wires going to the switch and checking voltage to ground on each wire. Use an analog meter because the reaction time on this type of meter is much faster. You should see voltage on one wire and none on the other. If you clearly find the Hot wire I would attach the voltmeter to the other wire and then wiggle, do not remove it, the plunger in the switch. If at any time while playing with the plunger you see voltage the switch is either bad or the plunger is not set in far enough the work properly.

Considering the age of your trailer you might consider changing the switch anyway.
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