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Problem With Braking While Pulling A Trailer...

TriSum

By TriSum
in Ask A GM Technician

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TriSum Enthusiast

TriSum

Posted
Posted

I have a 2007.5 C4500 C&C. I pull a 53' enclosed trailer with this truck. I'm having a problem when coming to a stop, below 30 mph or so, the truck starts to buck back and forth- it gets pretty violent. If I just use the trailer brake to stop, no brake pedal, it will act normal.

 

I tried pulling all of the abs fuse, (3 40 amp), and it did not change.

 

The trailer is new and I have pulled it with another truck and it does not do this.

 

Any ideas ?????

 

Thanks, David

TriSum Enthusiast

TriSum

Posted
  • Author
Posted
What do you have for a controller in the truck?

 

Ooops! I guess that would have been good information to include. It's a Prodigy.

 

Thanks,

 

David

compulynx Enthusiast

compulynx

Posted
Posted

Easy fix. It is a badly engineered brake light switch. To test, go to the truck, and set a mirror or get the rear close to a wall so you can see the lights. With the truck running, hit the brake. You will see the lights. Now, let off very slightly, I bet the lights go out. This was a defect in my 2008 model also. There is a new part #, I assume it it the same for the 4500's....

 

They modified the switch to have less spring pressure, so it would stay on if you let off slightly on the brakes....

 

There is also a TSB on this problem.

 

Here is what happens. Controllers like the Prodigy have what is called "Boost". This will send a pulse of voltage to the brakes as soon as the switch lights up the lights. The problem is, with the lights going on and off under light braking...the boost is pulsing on anf off, causing the jerking.

 

To test that, turn boost to 0, the off position. You will se a marked difference....

 

I put the new part # switch in, and presto, problem solved.

 

I am not putting the # here, since I am not positive the 4500 is the same #. Someone on here can verify if the TSB is the same part for the 4500 as it is for the 1500 and 2500.

 

TSB Number:08-08-42-003

 

 

ADDED: Found a thread on it..

http://www.gm-trucks.com/forums/index.php?showtopic=99425

 

C

TriSum Enthusiast

TriSum

Posted
  • Author
Posted

According to the parts guy, they are the same part number for all of the trucks. I will have them check this in the AM. I will post my outcome.

 

Thank you very much !!

 

David

 

 

Easy fix. It is a badly engineered brake light switch. To test, go to the truck, and set a mirror or get the rear close to a wall so you can see the lights. With the truck running, hit the brake. You will see the lights. Now, let off very slightly, I bet the lights go out. This was a defect in my 2008 model also. There is a new part #, I assume it it the same for the 4500's....

 

They modified the switch to have less spring pressure, so it would stay on if you let off slightly on the brakes....

 

There is also a TSB on this problem.

 

Here is what happens. Controllers like the Prodigy have what is called "Boost". This will send a pulse of voltage to the brakes as soon as the switch lights up the lights. The problem is, with the lights going on and off under light braking...the boost is pulsing on anf off, causing the jerking.

 

To test that, turn boost to 0, the off position. You will se a marked difference....

 

I put the new part # switch in, and presto, problem solved.

 

I am not putting the # here, since I am not positive the 4500 is the same #. Someone on here can verify if the TSB is the same part for the 4500 as it is for the 1500 and 2500.

 

TSB Number:08-08-42-003

 

 

ADDED: Found a thread on it..

http://www.gm-trucks.com/forums/index.php?showtopic=99425

 

C

compulynx Enthusiast

compulynx

Posted
Posted

One other thing. Even with the new switch, I have learned that if I will be in city stop and go traffic for a while towing, I turn the boost off on the Prodigy. Much smoother stops.

 

Boost works great on the open highway and mountains.

 

C

brims Senior Enthusiast

brims

Posted
Posted

I wish you good luck getting that switch. I'm still waiting on mine, I got jerked around for a month by the local dealer, then GM Parts Direct told me they couldn't get it, now I'm waiting for GM to get off their dead ass and start making the thing again as it's still on back order. I want to say 2-2.5 months by now.

TriSum Enthusiast

TriSum

Posted
  • Author
Posted
I wish you good luck getting that switch. I'm still waiting on mine, I got jerked around for a month by the local dealer, then GM Parts Direct told me they couldn't get it, now I'm waiting for GM to get off their dead ass and start making the thing again as it's still on back order. I want to say 2-2.5 months by now.

 

Well, the dealer my driver went to had 3 in stock, which was great. The bad thing is it did not fix the problem.

 

Any other suggestions ??

 

Thanks, David

TriSum Enthusiast

TriSum

Posted
  • Author
Posted

UPDATE: The dealer changed out the switch, but it did not fix the problem. I'm waiting to talk to my driver and see if it got any better or what. Will update.

 

Anyone else ?????

 

Thanks, David

 

I have a 2007.5 C4500 C&C. I pull a 53' enclosed trailer with this truck. I'm having a problem when coming to a stop, below 30 mph or so, the truck starts to buck back and forth- it gets pretty violent. If I just use the trailer brake to stop, no brake pedal, it will act normal.

 

I tried pulling all of the abs fuse, (3 40 amp), and it did not change.

 

The trailer is new and I have pulled it with another truck and it does not do this.

 

Any ideas ?????

 

Thanks, David

TriSum Enthusiast

TriSum

Posted
  • Author
Posted
I have a 2007.5 C4500 C&C. I pull a 53' enclosed trailer with this truck. I'm having a problem when coming to a stop, below 30 mph or so, the truck starts to buck back and forth- it gets pretty violent. If I just use the trailer brake to stop, no brake pedal, it will act normal.

 

I tried pulling all of the abs fuse, (3 40 amp), and it did not change.

 

The trailer is new and I have pulled it with another truck and it does not do this.

 

Any ideas ?????

 

Thanks, David

 

 

Well,...............................

 

 

 

It was the brake controller. I guess the Prodigy has an inertia switch inside and for some reason it doesn't work well with large heavy trailers.

 

Unbelievable !!!

 

Thanks all for the help.

 

David

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