Power voltage to brakes??

You have a bad connection somewhere. Does the other magnets show close to battery voltage? If so the area of problem is pretty limited.

ivbinconned wrote:
Never been happy with braking on our C Creek. Just installing all new brake assemblies and checked voltage at right rear and it shows only 9.5 volts!!
This is not via the truck. I have it connected directly to a tested 12.6 volt battery .
Should I see that kind of a drop from the battery?

No. Not normal.

Shouldn't have that much voltage drop, I would expect perhaps a few tenths of a volt drop due to wire resistance.

Sounds like you may have severe corrosion at some wire spices.

Or like one of my TTs, it came from factory with three splices between the trailer tongue and the first axle (near as I could tell the factory was using up all of the leftover floor drops on that TT that should have been discarded).. All of the splices were corroded.

You have the option of cutting and replacing every splice or abandon the existing wire and refresh with a much heavier gauge wire.

Typically RV manufacturers will use the lightest gauge wire they can get away with, it works, but due to increased resistance of the lighter wire and distance of the wire it will rob you of brake performance.

I used two pairs of 10 ga wire on my 26ft TT, made a large improvement over the factory 16 ga wire that I found they used.

Did you measure the voltage at the battery while loading it with the brakes? Maybe the battery voltage is dropping

I pulled the breakaway pin to test off house batteries and gained a volt. 10 volts.

following this thread,
I have a 18K weight TH and could not lock up the brakes, so I took it to a repair center and they found some problems and fixed them, but still could not lock up the brakes, so I asked them why not and they said cause of the weight of the TH, well I said I didn't have any problem locking up brakes on my previous TH that weighed 15K, they had no reply.

ivbinconned wrote:
I pulled the breakaway pin to test off house batteries and gained a volt. 10 volts.

Yep, you have a lot of voltage loss, most likely due to some very corroded crimp connections.. Not unusual as the RV industry does not use weather proof crimps and moisture wicks into the connection.. Corrosion of copper creates an dull oxidized layer which conducts electricity poorly.

However as one poster mentioned, while you have the battery under load, take a voltage reading at the battery and then compare that to the voltage at your brake magnet connections.

The reason for this is while you battery may read 12.6V or 12.8V when no load is present, it can sag considerably under load if battery is partially discharged or no good at all.

Something else to consider, the brake wire is run in a pair or set, both pos and negative ground are run from tongue to the magnets. You do not want to use the trailer frame for measurements as it may skew your readings if there is a bad ground or ground wire at the front of the trailer. Do not be tempted to connect the magnets to the trailer frame at the rear of the trailer, doing so may result in poor performance and may also cause your brake controller to not properly detect the brakes (IE No connection messages).

Once you have good reading of battery under load you can now better determine how to proceed.

If you have some decent wire (14 ga or 12 ga) laying around, you could temporarily connect that wire from the tongue back to the first axle (disconnect the existing wire from the connections on the front and at the first axle). The remeasure the voltage.

If you get almost the same voltage as the battery at the first axle, then you have an issue with the wire running from tongue to the first axle. If that is the case, I would simply abandon the existing old wire in favor of running fresh new wire. Trying to find and repair brake wires can be difficult depending on how they ran them.. My current TT those wires were run inside the trailer walls..

GottaRunGottaCamp wrote:
following this thread,
I have a 18K weight TH and could not lock up the brakes, so I took it to a repair center and they found some problems and fixed them, but still could not lock up the brakes, so I asked them why not and they said cause of the weight of the TH, well I said I didn't have any problem locking up brakes on my previous TH that weighed 15K, they had no reply.

You have an extremely heavy trailer, you may even have the same brake size on your current trailer as the old trailer. The brakes tend to run in "families" of weight ranges. For instance, I am familiar with "3500 lb" and "5200 lb" axles.

3500 lb axle brakes covers axles from 3,000-4,500 lbs or so with 10" drums.

5,200 lb axle brakes covers 4,500 lbs - 8,000 lbs with 12" drums..

Now with that said, you also have a very long trailer and looks like it is a 5th wheel version putting the axles further back. That means you most likely have more wire from front to the axles.. More wire run = more resistance = more voltage drop at the end of the run.

So, you have at least two problems..

More weight on the same size brakes.

More wire resistance due to longer distance of wire run.

You can do the same voltage checks, verify the battery voltage at the terminals under brake load. Then compare that voltage to what you measure at the brake magnets.

If you see more than one or two tenths of a volt less at the magnets you may need to consider upgrading the wire size to reduce the voltage drop over the distance.

If you do not detect much or no difference in voltage then the issue becomes more of the fact that the brakes may not be sufficient for your load..

Now, do be aware, locking up the brakes is not really needed and accidental lockup may be detrimental and now days many controllers cannot provide enough output to always lock wheels at full output. Not sure if any of the controller manufacturers even recommend that for setting up your controller any more..

You do want to be able to "feel" the braking effort when setting your controller up without locking up the trailer brakes. Each controller has it's own setup instructions so consult those instructions for proper setup steps.

On edit..

You can check Dexter Axles service manual HERE as a good source of info.

Dexter recommends the MINIMUM of 10 ga wire for 4 brakes and hitch to axle distance of 30ft-50ft (see page 11 of the manual) your trailer falls into the minimum recommendation of 10Ga. Note, you CAN exceed the minimum recommendations in wire size, won't hurt and may improve a bit better on performance.

Dexter also mentions "burnishing in" your brakes on page 11, this is a procedure which allows the brakes to conform to the drum properly faster than normal driving. When brake shoes are new, they may or may not always make full contact with the drum, so the brakes may feel weaker than they should until they wear in a bit. (I ran into that when I replaced my backing plates, took a few thousand miles before I had brakes that felt as good as the old ones).

Page 12 of the Dexter manual also states..

"Note: Not all trailer brakes are capable of wheel lockup. Loading conditions, brake type, wheel and tire size can all affect whether a brake can lock. It is not generally considered desirable to lock up the brakes and slide the tires. This can cause unwanted flat spotting of the tires and could also result in a loss of control."

The spec to measure is amps. s/b 3 amps per wheel. Use your DC clamp meter and post the results.

BTW when the truck is running... the source voltage will be 1 to 2 volts higher.

time2roll wrote:
The spec to measure is amps. s/b 3 amps per wheel. Use your DC clamp meter and post the results.

BTW when the truck is running... the source voltage will be 1 to 2 volts higher.

OP already has mentioned that they are only getting 10V at the brake magnets when they pull the emergency breakaway switch..

There is no way they will ever see 3A per wheel as long as there is less than 12.6V-12.8V at the magnets..

Actual current drawn by the magnets is governed by the voltage present at the magnets. Less voltage available at the magnets = less current drawn by the magnets.

Magnets on DC voltage look and act like a resistor, 12.8V at 3A draw means about 4.2 Ohms worth of resistance..

At only 10V they would expect to see about 2.38A per magnet or about 79% of the max braking effort that they should have..

They have a huge voltage loss somewhere and until they find where that is they won't have full potential braking effort.

Reading the current isn't needed or required for this troubleshooting and may cause one to run down some rabbit holes that wasn't needed.

Measure the current (I's use a clamp on ammeter first to make sure as most in-lines are limited to around 10 amps.

Then look at the wire size.. And length.

Then google Wire Size Calculator