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Old 07-01-2008, 09:11 PM   #15
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1969 31' Sovereign
Broken Arrow , Oklahoma
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Be sure to check the ground wire on the TV you may be getting the ground through the trailer ball. Pulling the brake-away pin provided the brake power from the trailer battery and uses the same wiring only a different path so that is a good clue on where the problem is.


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Old 07-02-2008, 05:22 PM   #16
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Thanks for the many helpful replies.

Last evening I replaced the break away switch. It was origonal equipment in a "99 trailer, so I thought that it would be a good step. I also applied some fine sandpaper to the brass leads in the electrical hookup cord on the trailer. They were a dull brass color: they are now shiny. The receptacle side on the truck appears as new.

This morning I went on a test drive. If anything, the braking ability seemed to be a bit worse. At 25 mph, regardless of gain setting (tried 6 and 10), or B1, B2, or B3 boost setting, the trailer brakes do little to stop the vehicle. When I returned from the drive I pulled one drum off and again checked the numbers at the magnet. The results were a little higher than I earlier obtained. With engine running, at full gain (13), voltage is 11.0, amperage is 4.1.

This evening I have recorded the following data (all with engine running):

-Battery voltage - 14.3
-At input to Prodigy - 14.3
-Output wire of Prodigy (full gain) - 13.7
-With lead run from brake magnet to Prodigy output wire - 12.6 volts. Used #12 wire with lighter wire clip wires on one end. This result falls within your definition of being close.

There are more measurements to be performed as listed in the post. More data to follow! I'm heading back outside.

Thanks, Steve

This evening I proceeded to start the diagnostic procedure laid out by Beginner. This is a progree report on the first couple of steps.

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Old 07-02-2008, 05:42 PM   #17
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1991 35' Airstream 350
Siloam Springs , Arkansas
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The posts and data seem well rounded. Don't forget the other half of the circuit. Make sure all is well grounded. The controller, trailer plug and the grounding points of the brake circuits at the axles. The current must make it back to the TV.
Jeff & Cindy
Hunter RIP

'09 27FB Flying Cloud
'91 350 LE MH
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Old 07-02-2008, 07:59 PM   #18
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1984 31' Excella
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Voltage Checks

You are measuring voltage, not current.
The lighter #16 wire will work just fine.
Remember, you have a resistance somewhere between the brake magnets and the controller or between the ground wire of the brake magnets and the negative post on the tow vehicle battery.
Only have the full gain selected long enough to make the voltage measurement (10 seconds or so), for this you need an assistant/helper.
You don"t need to have the engine running, just the ignition turned on.
Post results as soon as you get them.
Describe the points at which you made your voltage checks fully, this will help me.
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Old 07-02-2008, 09:57 PM   #19
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If you test the break away switch make sure you unplug the umbilical or you may fry the controller
Sail on silver girl. Sail on by. Your time has come to shine.
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Old 07-03-2008, 12:52 PM   #20
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I solved a similar issue by following any exposed wiring with my Radioshack infra-red thermometer. It showed a hot spot at a soldered connection inside many turns of insulating tape. Ten years of very slight moisture ingress had caused electrolytic corrosion between the solder and the copper wire. This caused the hotspot, the resistance, and the poor performance. A common problem is corrosion or a loose wire inside either part of the 7-way connector. I fixed this on an Argosy in the Florida Keys last winter, when the distressed owner had useless brakes.
Nick Crowhurst, Excella 25 1988, Dodge Ram 2500 Cummins Diesel. England in summer, USA in winter.
"The price of freedom is eternal maintenance."
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Old 07-07-2008, 01:07 PM   #21
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Here's a reply I got from Dexter about locking up the brakes in panic stop situations.

Hey Marshall,

One thing is that contrary to popular belief the trailer brakes are designed not to lock up. You can however get the brakes to lock up if you apply full force to them while on dirt or small gravel at a slow speed. If the brakes lock up when in full motion then it becomes a safety issue (especially with lighter trailers as yours) and that is why we don?t want the brakes to lock up.

Also refering to brake operating temperature:

If you can put your hand on the hub or wheel and leave it there for a few seconds then you don?t have anything to worry about. It is when you cannot stand to touch it without getting a burn on your hand that you need to worry. When it is that bad you can usually smell the hot pads on the brakes when you are close to the wheel area. I would say that you have nothing to worry about with them. As always, I am here to answer your questions.

Take Care,

Danny Gilbreath

Quality Manager

Dexter Axle Plt. 16
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Old 07-18-2008, 05:20 PM   #22
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Finally, we have some progress in restoring good brakes on the trailer.

A friend volunteered to help look for an electrical problem. To make a very long story short, we tried many things and could not come up with a significant problem in the wiring. We did add grounds.

I took the Airstream to a small local RV repair shop that was well recommended. They in turn looked for an electical problem to no avail. The first comment they made after inspecting the brake assemblies was that the brake drums appeared to have been replaced. I advised them that I was certain that those drums were original equipment. (I bought from the original owner, who in 4 1/2 years virtually never used the Airstream.) The brake assembly - backing plate, shoes, magnet, etc. were made by Dexter, which these folks consider to be the leader in the industry. The drums, however, were made by Reliable. While Reliable drums are OK, they said, they are not nearly as heavy as the comparable Dexter drum.

We decided to replace the entire brake assemblies and drums. We used an oversized one at that. There was some scarring of the magnet and drum surfaces, but no one that inspected them initially thought that they would not perform properly. However, the possibility of degraded magnets, magnet wires, and drum surfaces was the only good option left to us.

The good news is that the brakes are now working as expected.

The many folks on this forum were essential in narrowing down the possibilities. I thank all of you very much! Steve

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