Check for bad ground. has to be in the electrical of the trailer. Either the ground or damaged wires with high resistance.

 

How tight did you set the pads to the drum. You should have alittle drag. I run a double ground on mine. One the the frame and another to the plug. Ive bought a new brake pad setup that had a bad magnet.

Try jacking the wheel off the ground a spin it by hand. And see if they well lock up And check the voltage while doing it.

And ive always replaced drum and pads at the same time. Did you run the pads down the rivits. It mite have wore to much of metal out of the drum. So they mite be to big.

 

That's my first though.... the wires are all run through conduit which makes it difficult to trace them the whole way. I know that the main ground is good because I just redid it a few weeks back when I was having light problems. The 10ga wire coming from the brakes is grounded to the trailer frame and also to the vehicle (through the plug). That should be sufficient, right?

 

The drums have a little bit of drag right now. I tighten them up even more than that when I was trying to get the brakes to work, but it had little effect when driving.

I had both wheels in the air yesterday and spun them by hand. They stopped spinning instantly when the brakes were applied.

The old pads weren't worn very much. I just figured that my old magnets were weak, which is why the brakes weren't working very well. That's why I didn't replace the drums at the same time.

 

I would pull the saftey breakaway pin on the brakes and then try and drive away. The tires should be fully locked up by the trailers battery. It's got to be a bad connection somewhere. I assume you have at least 12 gauge trailer brake wiring too. I would check each connection, as most trailers use the crimp connectors and they corode after a couple years in the best conditions. You could allways cut and re crimp and use the heat shrink connectors. I've been adding conductive grease too, as it keeps the water out. My RV trailer had a bad connection, I tinned both ends solder them together and heat shrinked that mother, plus eletrical tape for extra insurance.
Measuring the voltage is a good place to start.

 

Time to get out the voltmeter.

Bare the brake wire right before it splits off to the axles, right by the axles. When you apply the brakes full on, you should see 12V there.

If you have 12V there, cut the wire and insert the voltmeter as a 20A ammeter. You should see 12A going to 4 wheels, 3A per wheel.

I bet the electrics are OK. I bet your drums are glazed, oily, dished or worn and your magnetic pucks can't get a grab on the drums to properly apply the brakes.

I'm putting electric over hydraulic disks on my new trailer.

 

I'm betting that the drums may be the issue too... I didn't even think about checking them out when I had them apart; not that I had new drums to put on there anyway. I'm going to check out the electrical tomorrow, and if it's good, I'll try to find some drums locally and throw them on there.

 

Best I can get is 10v at the wheels. Without the plug in, I get 12V from the truck.

Looks like it's time to start playing with the wiring. First thing to do is re-wire the plug. I'm going to use some ring terminals to make sure that I get a good connection to the plug. The grounds look and test pretty solid, but I will see if I can ground each brake at the wheel while I'm messing with it.

Other thoughts?

 

You've got a bad ground in the loop. Either where the brake controller grounds or where the trailer plug ground.

You might also have a short somewhere on the trailer that is causing a lot of current and thus the voltage drop.

12V should give you 12A. 10V should give you 10A. Magnetic pull varies as the current squared, so you should get 100/144 = 60% of the braking output with your wiring like that.

You should get 12V at the wheels with the breakaway wire pulled. How much braking power does that give ?

You'll need good drums/magnets and shoes as well as a good braking power feed in order for the system to work well.

I'd fix the electrical problem before I went any further.

 

Spent 3+ hours on it tonight and didn't make any progress. I added a new ground at one of the wheels and changed all of the connections for the existing grounds, but no change in voltage on the meter.

I may start 'fresh' tomorrow and just run two new wires for the brakes. Everything else is working fine, so no need to mess with the lights. All of my wires are run through conduit, so I can't visibly check the existing wire to check for shorts, etc. I ran out of daylight and didn't get to check the curent draw. If I check that, and it reads at 10A (assuming I still show 10V), that means that I don't have any shorts, right?

What size wire should I run if I start new?

 

I use a Jordon Ultima brake controller. It reads the amps right on the unit.

Each brake magnet is supposed to draw 3A. I think you have 1 axle with brakes = 2 magnets = 6 amps.

I would bypass the brake controller with a wire like you did and measure the current draw right at that wire. I'm guessing you are going to see more than 6A because there is a short somewhere and some of the current is going to ground. Then I would check the current draw at the wheels.

I don't know what to say about the wire size. The run is probably 30 feet and it only needs to carry 6A. There is a calculator here:
http://thecarpcstore.com/cms/index.php?option=com_content&view=article&id=47&Itemid=63

Don't feel bad. I once spend a day trying to figure out why my trailer batteries didn't charge properly when hooked to the truck. Voltage at the battery as 11.5 V, with 14 V at the truck alternator. Found 2 problems. Bad ground where the connector connected to the truck frame and a poor connection in the box buried deep within the pin box.

 

If I'm seeing 12V at the truck without the trailer plugged in, can I rule out a grounding issue on the truck?

The next time I mess with it, I will probably just hot wire it to the battery on the truck instead of having to go squeeze the lever everytime I want to check the voltage. Looks like rain tomorrow, which is a bummer because I'm trying to get this thing operational before a trip on Friday. Looks like it might be a late night on Thursday!

 

If I'm seeing 12V at the truck without the trailer plugged in, can I rule out a grounding issue on the truck?

If you are using the ground from the plug aswell, then yes... if not, how do you know that the ground is good if you are grounding the test lamp to the truck frame.

 

My thoughts as well. I was using the ground in the plug and getting a full 12v. When I switched to the trailer though, it dropped to 10v. I think I'll run new wires for the brakes and a new main ground tomorrow or the next day. Hopefully that will solve my problem.

 

If I'm seeing 12V at the truck without the trailer plugged in, can I rule out a grounding issue on the truck?

No. The ground needs to be good enough to pass 6A. It might work fine with a 100 ma test light.

To properly test the truck you might want to hook it to another trailer and measure the voltage at its brakes.

To properly test the truck circuit use the brake feed at the connector and the ground wire to the connector. I've seen lots of trailers that were incidentally grounded through the trailer ball because the ground wire from the connector on the truck or trailer wasn't working.

 

To properly test the truck circuit use the brake feed at the connector and the ground wire to the connector. I've seen lots of trailers that were incidentally grounded through the trailer ball because the ground wire from the connector on the truck or trailer wasn't working.

I think I've done this... I had the volt meter connected to the truck plug for both hot (trailer brake wire) and ground. It was reading a little over 12V, just like the battery.

 

You can also measure the ground wire after the brakes. Measure from ground wire to ground trailer, this will give you the difference in potential if you have a bad ground. The entire voltage should be used up by the brakes.

You see no voltage, but if you see something it is power being used to get through the resistanceof the bad ground. Google measuring voltage drop.

You can also measure across any connections checking for voltage drop. Put one lead really close to the trailer plug, other lead next to brakes, if you see anything, it is voltage drop across the wire. You may get point (.) something, but should be minimal.

Remember a meter measures the difference of porential, this is how the voltage drop measuments work, you may have 12v on one side of a connector, then 10v on the other side of it. Putting the leads on each side of the same wire should read zero, if not then you are seeing the diffference in potential. In this case it should be 2v.

Hard to explain in writing. Hope this makes since.

I dont think I get a full 12v on the brake wire, never measured it that high. Also I only run my controller on 1 up to 2. So even with your drop, I think you would have plenty of braking. My 16 with one axle will not drag a tire on asphalt, try it on gravel and see. Mine will easily lock up on gravel.


VOLTAGE DROP TEST

A voltage drop test is the only effective way to find excessive resistance in high amperage circuits. It's a quick and easy test that doesn't require any disassembly and will quickly show you whether or not you've got a good connection or a bad one.

To do a voltage drop test, you create a load in the circuit that's being tested. Then you use a digital volt meter (DVM) to measure the voltage drop across the live connection while it is under the load. Voltage always follows the path of least resistance, so if the circuit or connection being tested has too much resistance some of the voltage will flow through the DVM and create a voltage reading.


Read here

http://www.aa1car.com/library/voltage_drop_testing.htm

 

While we're on the topic, is there a trick to figure out how much drag the brakes should have when you're adjusting them? I'm always worried I'm going to glaze the lining or something.

 

For wire, I use the low voltage wire from from HD or LOWE's. It's not colored but only one wire has writing on it and it has thick insulation. I use the 12 ga. etrailler has the right stuff that looks like romex ( but stranded wire). http://www.etrailer.com/p-10-2-1.html Leave a big service loop and just tape or ty-rap it on the axle. Makes it a lot easier to connect to the hubs.

As for the brakes they are just like other drum brakes, but the magnet drags and makes a scraping noise. So adjust them by feel. Adjust them out until you notice the hub starts feeling tight and then back it off until it spins freely.

Get a prodigy brake controller if you don't have one. I've run others and this thing is worth dough.

Your on the right track when you used the battey right at the trailer plug.

 

I believe it's already wired with 12AWG, but I'll have to verify the size. I know that it's 14AWG at the smallest.

Brakes are adjusted pretty good right now. I will probably order some new drums and throw them on just to be sure that the magnet has a good surface to grab. Even with only 10v, I think the brakes should be working better than they are right now.

 

I've always been told that when adjusting trailer brakes to keep tightening them until you completely lock the wheel up and cannot turn it. Then back the adjuster off until you have light drag. This is supposed to recenter the shoes in the drum.

 

I'm no mechanic or even play one on T.V., but I've worked a my share of drum brakes over the years. What you said is correct. But they have you tight them up as they what you to take out all the play in the shoe from moving up and down. You could have one shoe higher or lower than the other and this will help align them up and down to be centered. The slight drag is with new shoes as they never seem to fit your drums perfect and this will wear the pad a bit and then you will have full contact after a while. If your checking the adjustment as part of a PM. Then tighten them and back off until they turn freely as they are now matched to your drums:grinpimp: my .02

 

Replaced the drums today with some new ones.... brakes work worse now than before. I confirmed 12.5v - 13v at the wheels with the truck running. The brakes technically work (they stop the tires from spinning when in the air), so I know the magnets are engaging. Shoes are adjusted to a slight drag. Tried adjusting them tighter and looser, but no change either way.

Any ideas?

 

I think it may be time to take it to a local trailer supply shop? Might be worth it to bite the bullet and take to an expert. There's only soo much help guys can give you on a forum, sometimes it's just easier to have somebody look at the thing... But that's just my .02

 

it may be time to take it to a local trailer supply shop

My thoughts as well. Now I'm wishing I would have just done that from the start....

Brakes are on the correct side. The control arm of the magnet is pointing forward.

 

Brakes are on the proper side of the axle right?

 

I had a mechanic/friend tell me that the Ford controllers do not operate at
low speeds or in reverse.

I had concerns about my trailer brakes with similar issues.
Try pulling the breakaway switch and checking function.

 

I scanned through the thread real quick, and didn't see any mention of this. Have you tried taking a car battery and connecting it directly to the brake magnet using short pieces of heavy wire for both the positive and ground? That would definitely rule out any wiring or brake controller issue and point you directly to a magnet/drum problem.

 

Does your meter have an amp setting? Most do even the $2 H.F version.
You should get an amp reading too. It was mention before, like 2.5-3 amp draw on the brakes per magnet. If the ammeter is at the plug, you will get the total current draw from all magnets. If the ammeter is connected at one of the magnets, you will measure the current draw through that magnet only.

Note: The brakes should be wired in parallel, not in series. You need to have both a power and ground wire running to the magnets and not just grounding one side of the magnet to the frame.

Pic's Pic's Pic's Sometimes a good, well focused picture can tell a thousand words.