5th wheel brake issues

[RobertN]

I am puzzled by my 5th wheel, and trying figure what to check next...

My 5th wheel just does not have great braking. I replaced the front shoes when I got it two years ago(checked brakes, repacked bearings ect). Last couple of trips, braking seemed marginal at best; it felt like they dragged, but no real braking, so I put it on jackstands.

I would not say they have been great since I got it, but they seemed to be ok. Probably because the front brakes were working overtime. And, the controller was turned WAY up. It was a 8 year old unit when we got it.

I leveled the controller per the controller booklet.

- It is a 27' Wilderness 5th wheel, 7500lbs GVWR; it is not big, nor very heavy. And, we have it lightly loaded.

- The front axle brakes appear to work fine. The shoes I installed two years ago have ok wear.

- The rear brakes were not wired properly. The positive went to the left rear brake, and the negative to the right rear brake. The shoes appear to have more than 50% lining.

- Before we did a trip to the coast in July, I adjusted the shoes; they still seemed in adjustment per the book.

- Before correcting the rear axle wiring, I checked the front axle. I could hear the magnets buzz when my wife used the manual function on the controller. But, I only had 8V at the magnets(at the crimp on the pig tail). The connection was soldered...

- After correctly connecting the back axle wires, the magnets on that axle buzzed when the controller was manually operated. The voltage at the front or rear brakes, was only 6V now when the brakes are activated.

- The magnets all ohmed out at 3.2ohm, as per the book.

- Current at each brake was about 1/2 what the book says, which makes sense as the voltage was 1/2(6V vs 12V).

- The controller adjusts properly per the manual. It is a 12 or so year old Tekonsha Sentinel. It is supposed to be able to handle 8 brakes(4 axles).

- FWIW, the brakes did not seem to work that great on my flatbed trailer with the tractor loaded. It is a 7klb trailer, brakes on one axle. It is close to capacity with my tractor loaded.

 

[Diamondpilot]

I read the first two lines and can all ready tell you what your issue is. Trailer manufactures take every short cut in the book. I have seen it many many times over and the problem is you either have 18 or 16 ga wire going to the brakes. You need 12 ga min for that length of a run, aprox 25 from the pigtail. I would go with 10 ga myself.

Look it up. Many sites recommend 12 ga wire for 2 brake axles under 25' and 10 ga for 3 brake axles and runs longer than 25'


I will bet you a steak dinner this is your issue if you do indeed have something less than 12 ga wire.

Chris

 

[slowzuki]

Also, what is the grounding wiring like? The current needs a good complete circuit for both the positive and the ground. Are you getting a proper 12V at the truck connector to start with? Do the magnets pull in proper if you hook a battery directly to each one individually? Any hidden scotch locks or damaged wiring?

 

[RobertN]

The Dexter book for the axles/brakes says minimum 12g too. It is 12g. Ya, the IR drops across 18g would be terrible.

I have checked wiring and grounds thru the trailer. I need to open up one of the connectors to get voltage at the truck. I did try both connectors; I have the "T" so there is one in the bed, and one on the receiver hitch for my other trailers.

I have had ground issues with trailers before, so that was first on my checklist.

 

[Bird]

Robert, I also wonder about the size of the brakes. When I bought a 1988 CarriLite 32' 5th wheel, they had built it with 3,500# axles. But since I had it rigged with not only air-conditioner, but generator and washer/dryer. Anyway, it turned out that I had 7,300# on the axles. Brakes weren't too bad, but when I had everything from the frame down replaced with 5,200# axles and bigger brakes, both in diameter and width of the shoes, the difference in the brakes was like day and night. That was with the same wiring and brake controller.

 

[Diamondpilot]

One other thought that came to mind after reading Birds response. I had a customer with a 7,000# camper with 205/75/15 tires. Everything worked great. He wanted me to order new wheels and tires and he wanted to upgrade to a D range tire. Smallest we could get in a Radial was a 225/75/15. Going up from a 205 to a 225 or about 2" bigger tire made the brakes about 1/2 as effective. It would push his 1/2 ton GM around pretty good.

Have you changed the tire size?

Chris

 

[RobertN]

I did not, but previous owner did. Tire specced on trailer tag and in manual is 205/75/15. It has on it, 225/75/15.

I know from lifted 4x4's with big tires, big tires = less effective braking...

When I got it two years ago, everything did work better though...

Have you changed the tire size?

Chris

 

[Ken45101]

You are going to have to find where you are losing the voltage, both 12v and ground. Run a ground wire from the truck battery back to your voltmeter. See what voltage is on the ground wire at the brakes. And of course find out where you are losing the voltage on the hot wiring too.

Ken

 

[Reg]

What you need to look at is the CURRENT that is being drawn (as well as the voltages).
If you have or can borrow a battery charger with a decent ammeter on it hook that up directly to the trailer plug's brake and ground wires, you should see 12 amps being drawn.
If that checks out OK at the trailer plug the chances are good that you have high impedance somewhere in the truck.

 

[psj12]

While looking at the gage of the power wire in the trailer don't forget to check out the power wire in the truck. It should also be 12ga or better. The ground wiring between the trailer and truck, and the ground wire on the truck should be of equal gage as the power wire. While grounding will occur through the mechanical trailer connection you cannot depend on that.