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Old 05-01-2016, 07:06 PM   #1
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trekerboy's Avatar

1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 256
Trailer brakes feel too sensitive, "grabby"

I have a Prodigy P2 brake controller that I've only really used a handful of times, and recently I noticed that sometimes even the lightest touch of the brake pedal will about send me through the windshield (read: way too sensative)! It doesn't seem to happen all the time, but once it does happen that behavior persists for the rest of the drive.

Is this more indicative of a brake controller setup/setting problem, or of a problem with one of the trailer brakes sticking?

Anyone who's experienced this issue I'd welcome your input. AS is '79 Excella 500 31' remodel.

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Old 05-01-2016, 07:28 PM   #2
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Alcoa Roller's Avatar
1963 26' Overlander
Dallas , Texas
Join Date: Sep 2009
Posts: 88
I assume you have not tried adjusting the brake controller??? That would be my first suggestion. There should be an adjustment wheel on the controller that will increase or decrease braking on the trailer when you apply brakes in the vehicle. Get to a parking lot and test it out.

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Old 05-01-2016, 07:32 PM   #3
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2000 19' Bambi
mt. Prospect , Illinois
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Have you adjusted the controller? Sounds like the voltage output is set too high. When stopped, you slide the emergency stop lever over to the side and hold it there. The output voltage is displayed. Turn the wheel on top left to reduce the output current. Drive off and slide the emergency stop lever. The trailer should stop you smoothly. Try again and adjust the voltage up or down until you like the feel.
No WD, but a great DW!
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Old 05-01-2016, 08:03 PM   #4
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1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 256
Originally Posted by robert claus View Post
Have you adjusted the controller? Sounds like the voltage output is set too high. When stopped, you slide the emergency stop lever over to the side and hold it there. The output voltage is displayed. Turn the wheel on top left to reduce the output current. Drive off and slide the emergency stop lever. The trailer should stop you smoothly. Try again and adjust the voltage up or down until you like the feel.
From what I've read, the way to properly set the brake controller gain is to find the setting that, when applied, is just before the point that the trailer brakes would lock-up. That point for me is 9.0... any higher than that and pulling the emergency lever on the trailer brake controller would lock-up the trailer's wheels.

I adjusted the gain all the way down to 7.5 and still had the issue. I'm weary to go below this setting because beyond that it seems like the Tow Vehicle is doing more of the stopping than the trailer's brakes are.
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Old 05-01-2016, 11:56 PM   #5
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2015 27' Flying Cloud
Washington , Washington, D.C.
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Drum brakes, unlike disc brakes, are self-actuating. That means that, once engaged, they will brake harder without any additional "pedal effort" being applied. Back in the day when auto brakes were of this type and were not power assisted, this was a feature not a bug. I've noticed the same issue with the built in controller of my GMC truck. This appears mostly at very slow speeds or on wet pavement and sometimes after the brakes have had a lot of use. I did dial back the gain on my controller half a step, which made it less objectionable. But it's still there.
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Old 05-02-2016, 12:04 AM   #6
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1972 31' Sovereign
1975 31' Excella 500
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Benton , Arkansas
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When the brakes are just wearing out of adjustment they can get grabby because of the above mentioned "self energizing" feature of drum brakes becoming exaggerated when the shoes get a little lose.

If your brakes are auto adjusting, you have to apply the brakes while moving backward for the auto adjusters to work.

Superat stultitia.
The fact that I am opinionated does not presuppose that I am wrong......

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Old 05-02-2016, 04:41 AM   #7
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1977 31' Sovereign
1963 26' Overlander
1989 34' Excella
Johnsburg , Illinois
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Only the leading shoe on drum brakes is self activating. Electric brakes have mechanically amplified braking, due to the friction on the disk portion of the brakes. Test on asphalt to see if only one of your trailer brakes is locking up. Take that one apart and examine the electric magnet surface as well as the surfaces of the leading shoe and drum brake surfaces. Repair as necessary. If you are not mechanically trained, leave it to professional trailer brake repair people.
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Old 05-02-2016, 10:08 AM   #8
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I set em so I feel a little tug when I brake
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Old 05-02-2016, 10:53 AM   #9
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2009 28' International
Pacific Palisades , California
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Posts: 315
Not familiar with your particular brake controller but in many there are two different places to adjust. One affects how quickly the brakes engage and the other the strength of the engagement.

It sounds like it is the first one (the one you would seldom adjyst( that you need to find and adjust.

I need to do this myself as I'm having a mild version of your symptoms, but only at slow speeds. I think I accidentally adjusted the wrong one the first time we used the rig this season, so I need to yank out the manual and readjust. On mine, on the less frequently used dial, I think they give you three gross engagement settings for different size and weight of what you're towing--up to a 15,000 lb fifth wheel. I suspect that I'll find that I'm on that very aggressive "initiation of engagement of brakes" setting!

If you can find your "initiation
of engagement" setting and make that milder (after the TV brakes engage) you can then readjust your other setting. You'll readjust that one more often.

We adjust the second one "on the fly". I can reach down and find the button and see the digital readout for numerical confirmation and set it up (more trailer braking in proportion to TV braking) when going down steep grades and/or at high highway speeds. Then I back it off for stop and go traffic around town. While my wife is driving, I adjust it for her at her request as we go. Either way, I do it in small increments and then test with (always verbally pre-announced) gentle braking as we go to dial it in perfectly for the current conditions.
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Old 05-02-2016, 12:46 PM   #10
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1996 25' Excella
Tillsonburg , Ontario
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It is possible that your ramp-up or delay adjustment is wrong; the brakes are just coming on full force too quickly.. It is also possible that the sensitivity that adjusts the amount of braking to the deceleration of the TV is set too high. Work on all the things noted above. I don't have the Prodigy controller so I speak only from general knowledge. Prodigy is a pretty good controller, unlike some of the cheap ones they sell for small SOBs at some dealerships that rely on slowly increasing the voltage over a short period of time. That only works for one speed, not the whole range.
If you are experiencing intermittent problems you likely have a bad ground or a resistance in the connector on the brake circuit. The applied voltage from the controller is probably constant; you can see it on the controller I believe. So when you adjust the brakes to an acceptable performance level to overcome resistance, and then suddenly the poor connection gets better the applied voltage is now too high...grabby brakes. This would be why the symptoms stay for the rest of the trip....better connections. I scrapped a perfectly good controller way back, only to discover my ground was poor.
Trouble with poorly adjusted drums is usually constant; the brakes always grab.
Trouble with morning humidity will result in grabby brakes until the drums heat up and dry out. Intermittent grabbing of one wheel may be sticky linkages that prevent the springs from pulling the shoes back off the drum.
If the brakes are too loose they will be grabby because of the self acting nature of the drum brake as noted above. The magnet develops a lot of leverage when the shoes are too far from the drum and the magnet swings further until the shoes make contact.

In your case do the brakes respond to reducing the voltage? If not then try the other adjustments. I believe the standard for adjusting brake voltage is still to adjust the control and then do a panic stop from 20mph using just the lever on the controller. Brakes should be just shy of lock up. Then a panic stop on the whole rig will apply just slightly more voltage to the brakes. If you get that right then you start on the two other adjustments, following the steps in the manual.
BTW you're not the only one who finds this a challenge!
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Old 05-02-2016, 01:08 PM   #11
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2013 25' Flying Cloud
Edisto Island , South Carolina
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I had much the same issue with a Prodigy P3, but only at very low speeds such as those in a parking lot or at traffic lights. Sometimes I would manually turn off the boost under those conditions but it was still somewhat grabby. Under all other conditions I was very pleased with the Prodigy. But that low-speed issue finally convinced me to switch to a DirecLink controller. It does not have the issue. Is yours grabby at all speeds or only at low ones?
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Old 05-02-2016, 01:47 PM   #12
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2014 25' FB Eddie Bauer
Vero Beach , Florida
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I use a P2 myself. Had it on multiple trailers. Three thoughts: 1. Posters above have nots to lower the max voltage which is done with the thumb wheel on the left side of the P2. 2. The P2 has a feature that allows you to adjust how hard the trailer breaks activity when breaking is detected. The blue button on the to right of the controller adjusts that setting. If your trailer and TV are similar in weight you should use the b1 setting. A lighter trailer gets just b and an heavier trailer goes to b2. There is a b3 for super heavy lads. Experiment a bit to see which you prefer. Our truck and trailer are close. I like b1 for my setup. 3. When we get started for the day the trailer breaks are always really grabby. I've apologized to my wife at just about every dump station stop for nearly throwing her through the windshield. If the problem is only the first few stops you can reduce voltage as you get rolling... Just don't forget to crank it back up.

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