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Old 07-30-2003, 09:39 PM   #1
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Question Prodigy indicating short and/or overload

Hi,

I'm trying to trace a brake fault (I think...)

Here's what I know:

When I'm parked and hooked up and pull the manual lever on my Teshonka Prodigy I get a good voltage indication on the LED and I can hear the brakes engage on the trailer. I can run the volts from 0.0 to roughly 13 with no problem.

When I'm rolling, whether I pull the lever or depress my brake pedal I generally get an "oL" indication on the LED (which my "manual" says means Overload.) About half the time, when I release the brake pedal or lever I get "SH" on the LED (which the manual says means the brake controller "sees a short.") If I don't get the short indication I get the ".c" for "connected."

If I turn the power knob almost all the way down the indicator shows 0.0 ... 0.1 ... 0.2 (I can see it working...) But if I move the knob even a bit more, "oL."

When the "oL" or "SH" indicators are showing my truck keeps rolling without any obvious braking from the trailer brakes...I haven't figured out how to drive, manually brake and run along next to the trailer listening for brakes :-) ...but I don't think I'm braking in this situation...

So what's wrong? I can't find a short on the wire (and would a short also show overload?) I popped the breakaway switch and nothing happened (problem for the future.)

How do I test to see if it is the wiring, the brakes, my controller, my truck wiring, the resistor...(etc.) Any ideas?

Hoping I'm an idiot and someone'll have a simple answer...but any ideas appreciated.

Thanks...

Bob

(Maybe I should take it to the hitch guys who installed the controller...but I'd rather figure it out without them... -B)
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Old 07-30-2003, 09:52 PM   #2
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Prodigy indicating short and/or overload

Greetings Bob!

When I had similar problems with the brakes on my '64 Overlander, a big part of the problem was with corrossion in the Bargman Connectors - - both the trailer end and the tow vehicle end. Once the Bargman connectors were replaced on both the truck and trailer ends the vast majority of the problem was solved. The balance of the problem was resolved about 30 days later when the brakes were overhauled with fully loaded backing plates.

Good luck in locating your brake gremlin!

Kevin

P.S.: I hope that you don't encounter something like was recently found on my Minuet - - wiring to the brakes had been pinched between the bellypan and frame rails resulting in a short - - it took dropping much of the bellypan to find this problem.
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Old 07-31-2003, 09:01 AM   #3
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Well, I'm assuming you have a multi-meter. If you don't, you can pick one up at Wal-Mart or wherever. First, unplug the trailer and see if you still get the short when you manuallly crank the controller lever. If you do, the short is in the truck wiring. If you don't, the short is in the trailer wiring.

Let's assume that the short is in the trailer wiring. Chances are pretty decent that it's either a fault in one of the connectors, or in the brakes.

Plug the conneting wire into the truck, and unplug the end of the connector that plugs into the trailer, and see if you still get the short. If you do, the short is in one of the connectors, or (relatively unlikely) in the wire. If you don't get the short, the problem is further down.

Here's where the multi-meter comes in. You'll want to undo both wires on each of the four brake connectors, in turn. Check the resistance of each brake coil, by setting the multi-meter on "Ohms" and connecting both of the test leads to both of the brake wires -- use the ends of the wires that are connected to the brakes, not the ends that are connected to the trailer.

Chances are that one of the brakes will test much, much lower in resistance than the others - maybe two, even. Those brake coils are then shorted out and must be replaced.
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Old 07-31-2003, 09:21 AM   #4
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If a magnet is extremely worn, namely down into the wire coil, a short will show , "when towing and activated," but will not show when at rest.

The controller nor a ohm meter will show that short, unless the whell is spinning.

Best way to check, is examine the magnets. The proper wear pattern for the round magnets is straight forward. When the surface of the screws in the magnets show wear, that's it, it's over. To allow the magnets to wear beyond the surface of the brass screws is asking for trouble.

Andy
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Old 07-31-2003, 09:30 AM   #5
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Now, there's the word of someone who really knows what he's talking about. Thanks, Andy!!!!
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Old 07-31-2003, 11:08 AM   #6
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I was helping a friend with some issues on a trailer and finnaly traced it to bad ground connection between trailer and tow vehicle. The trailer was trying to pull ground through the ball and when it couldn't pull it through the ball it tried to pull it through the lights. So brake lights would work with running lights off but not with them on. With the running lights on they would work till you hit the brakes and then all the lights would flicker or go off. It also made the turn signal indicators on the dash glow.

On the tow vehicle side there will be a ground wire that goes from plug to frame (White I think but double check that). GM vehicles are notorius for lack of ground on the frame. I know till mid 80's there was NO ground strap from frame to body. The ground path was from battery to engine block from engine block to fire wall. Once they startd Fuel injection they started ground the frame better so they could ground the fuel pump to it.
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Old 07-31-2003, 11:25 AM   #7
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Well, *wow*...

Each time I ask a question I get tremendous advice. Thank you all!

Since I don't want the problem to be in the wiring (!) ...and, from what I can tell (and everyone says) Andy *knows* his Airstreams... I'm going to pull the wheels and look at the magnets this weekend...

...well, I'm going fishing one day, so the work will be on the *other* day...

Is there a guide anywhere that can walk me though the brake inspection? Are the magnets generally available or do I get to finally buy something from Andy? (I'd buy there in any event, but I'd like to do the fix this weekend if possible...)

And, while I'm looking at the brakes, is there any thing else I should look for?

I've got the multi-meter and assorted electrical "stuff..."

Thanks again (and again...)

Bob
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Old 07-31-2003, 12:55 PM   #8
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Bob.

Look for loose studs on the magnet arm. Look at the adjuster springs. If they are old, they will break when you least expect it. That in turn, destroys the drum and shoes.

Most owners change the adjuster springs evry few years, just to be on the safe side. It appears that they crystalize from tremendous heat to cool, many many times. Once they become brittle, that's it.

Check the grease seals. They could be leaking. It is wise and prudent, to never reuse any grease seal. They are not that expensive.

Also check the shoes, for wear and "cracks." If so, they must be replaced.

Andy
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Old 09-01-2003, 08:38 PM   #9
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Hi --

It's been a month, but I finally got to pulling the wheels and taking a look at the brakes... ...to my (inexperienced) eye, they don't look so bad...

I've attached a picture of the more worn of the two magnets. If you can see something I can't Please Please tell me!

And, I've got a couple of questions...

First, what is the proper wire run inside the brake? On one side I've got a wire that enters the brake and goes up to the arm the magnet floats on and then follows the arm ll the way to the magnet. On the other side, the wire goes pretty directly (with some play) to the magnet (i.e. does NOT go up and over the hub.) Does it matter? Which is right?

Second, I've got a shiny spot about an inch and a half long at the top outside edge of the front curved plate the pads adhere to. This looks like a wear spot. Do these parts adjust or do I need a replacement (or is it okay?)

I still get the short/overload indication...any ideas appreciated.

I've got more pictures. Let me know and I'll shoot them over.

Bob
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Old 09-02-2003, 05:13 AM   #10
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Bob.

When the wear on a round magnet is "flush" with the "top" of the three screws, it's over.

The magnet you have shown, is fine.

Magnets wires can be routed several ways. It actually makes no difference, as long as they are floating.

When working on electric brakes, it is wise to check the breakaway switch, AND, the magnets. Pull the breakaway switch pin, and check each magnet with a heavy weight, such as a hammer. That operation will check the switch and all the magnets, to make sure they are electrically ok.

CAUTION!!!!!!
Do not leave the breakaway switch out more than "5" minutes. To do so, can and will burn up the magnets.


Have no idea about the shiney spot. Another photo??

Andy
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Old 09-02-2003, 09:43 AM   #11
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Hi Andy,

Thanks -- When parked and when I depress the brake pedal I can hear the magnets on both sides (so I thnk they are working.) The problem comes along when I brake the moving vehicle.

Quick question: Is there a resistor or something in the circuit of a properly configured Prodigy that could be either mis-functioning or not there? (I didn't do the install...) The reason I ask is that when I have the Prodigy turned *way* low, I don't seem to get the problem as often, if at all. I was thinkgin that a bad resistor might allow too much power through giving a false indication of a short or overload?

Bob
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Old 09-02-2003, 12:44 PM   #12
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Bob.

Since you have a meter, measure the current drain of the magnets.

Measure it on a sliding scale, and lets see what readings you get.

That's the real test for a short or overload.

You could also, have a bad controller.

Andy
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Old 09-02-2003, 02:47 PM   #13
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Here is a bulletin from Tekonsha that was sent to me, I dont know if this helps in your situation but it cant hurt to post it ! Here is the url http://www.tekonsha.com/files/Techni...2020020060.pdf
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Old 09-03-2003, 02:27 PM   #14
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Hi...

After Andy's note and the post from 71Tradewind, I decided to ask the guys at Tekonsha. Here is their response:

"Hello Bob;

"The Prodigy showing the SH is definitely a short. OL is an overload condition which does indeed go along with the short. There is a short on the blue wire and what is happening is a brake wire is putting power back onto the blue wire and that is causing an overload. This is typically found on the trailer side of the plug or in the plug itself. You definitely have a problem here that needs fixed before your brakes will work properly.

"If I can be of further assistance, please let me know.

"Have a Great Day !!

"Charlene Clark
Technical Service
Tekonsha Towing Group
888-785-5832"

So I'm going to take my preconceptions out of the loop and rebuild the Main connector at the head of the trailer. If I still have a problem, then I'll disconnect one brake and then the other to see if I can isolate this.

I *am* going camping this fall. I am.

Thanks,

Bob
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