HOW TO: Brake wiring is UNDERSIZED. Some answers and partial solution....

[John E Davies]

Dexter specifically cautions the installer to use large wires for the electric brake system. From the service manual here https://www.dexteraxle.com/docs/default-source/default-document-library/light-duty-electric-brakesc67a839d2ba463c18d7aff64007a4014.pdf?sfvrsn=0

 

[attachment file=Dexter electric brake wire guidelines.png]

 

Oliver installed grossly undersized wires on my trailer. I do not know what size main wire runs inside the hull, but in the left wheel well there are two pairs of 18 AWG wires, one for each axle. the white wire is the supply wire, the black wire is the Dexter wire that crosses over to the right side brake:

 

 

The Dexter wires are a connected pair of 20 AWG wires, running through the hollow axle tubes.

 

I have been chasing a problem where the left front brake is doing way more work than the right front. It overheats, gets grabby and I am afraid that it is going to ruin the brake by frying the linings, grease and seal. I have been into the brakes two times, taken them apart, lubed everything and haven't been able to improve them. Before ordering new brakes I decided to upgrade the wires, just to make sure there was not an issue with too much voltage loss.

 

I bought a really nifty miniature inductive ammeter to do some measuring. It is a fantastic tool and I strongly recommend one for your emergency kit. It has a built-in VOM (volt/ ohmmeter with leads) as well as the inductive amp gauge function. ... https://smile.amazon.com/gp/product/B00O1Q2HOQ/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

 

To use it, you must have the wire separated from any others in the bundle. It will not work with two or more wires at once. I pulled the breakaway switch cord and measured total amps going back to all four brakes:

 

 

Specified current is 3 amps per brake magnet at 12 volts. I was plugged in, so shore power had my battery at 13.2 for the start of the test. The little wires coming off the switch get pretty hot, they are undersized too ;(

 

I measured each brake current separately. Right front:

 

 

Left front:

 

 

The other two were similar and I noticed that the right ones were drawing slightly less current than the left ones. That could have been variations in the magnets, or it could have been a crimp connection problem or those darned undersized wires. I decided to run larger wires across each axle to eliminate any voltage loss due to the too-small Dexter wires. There was nothing easily done about the factory wires without digging around underneath the battery compartment inside the trailer and running new big wires. At least there were two undersized wire pairs, not just one. Here are the factory crimp connections:

 

 

Note there is some clear silicone on them where I was checking voltage with a sharp probe last week.) They showed no signs of corrosion and appeared to have been crimped with the correct tool. I cut them all off. I bought weatherproof butt splices to replace them with, These are really expensive at Ace Hardware, $5 for three. They are way cheaper in bulk from eTrailer or Amazon.

 

 

I used 14 AWG stranded wire that I already had. It is still not large enough, but it is way bigger than the feed wires coming from the hull. Going even larger would not accomplish anything. The benefit of this size is that one 14 AWG wire will fit in one side of the splice, and two 18 AWG wires will fit in the other side, for a neat, snug connection. When crimped and shrunk, they make an exceptional connection for three wires or two.

 

I pulled the old wires out of the axle tubes and tossed them in my recycle bin. I ran the new ones along the outside of the tubes, on the back side so they will be protected from stones. Why outside? The inside wires are loose, banging and scraping inside the tubes and there is no way to inspect them without actually removing them. Wires on the outside are easy to inspect and they will not move around if properly secured. The right side splices:

 

 

The left side splices, where the feed wires join:

 

 

The wires secured to the tubes, and split loom added where they cross the U-Bolts:

 

 

Before securing them at the ends, I rechecked the amps, and found a slight improvement. Left front:

 

 

Right front (measured from the wire near the left brake):

 

 

So, at this point I knew my brakes were in good shape internally and the wires were not causing any problems. I tested the brake performance using my infrared remote temp gun, after going down a 1 mile, 300 foot descent, using no engine braking. The left front was still getting hot, and the right front was still not really doing much but the temperature delta had dropped from 100 degrees to 90 degrees, probably an insignificant variation. I doubt the wiring change helped any.... You could sure smell that left front brake.

 

Temperature, degrees F, max reading:

 

LF: 244

 

RF: 155

 

LR: 200

 

RR: 205

 

If  I can get that LF down 50 and the RF up 50, they would all be working the same, providing even and worry free braking. Time for a new set of brake assemblies on the front axle. I hate electric brakes, there are so many things that can go wrong with them, and the only way to inspect them is to disembowel them... Disc brakes are scheduled for the winter.

 

John Davies

 

Spokane WA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[John E Davies]

Suggestion, test your brakes as described, in a controlled setting, to see how hot they get. If one or more is hot or cold in relation to the others, you have a problem.

 

If you are willing and able to do your own work, you can futz around forever and try to figure things out. If you have to pay a shop $100 per hour, then just have them install four new brake assemblies, and YOU supply the brakes, Otherwise they will charge you full MSRP or even higher.

 

Buy your brakes at eTrailer, they are cheap and you will save a lot. Be aware the shop will not be happy and they will not offer their own warranty on the parts, just on their labor. But Dexter has a five year limited warranty on their brakes, so you should be able to get reimbursed from them if there is a problem later.

 

This is an Old School "manual adjust" brake, which I strongly recommend. The self adjusting ones just do not work well and they add extra springs and friction points to cause drag. These are the ones I ordered....

 

https://www.etrailer.com/Accessories-and-Parts/Dexter-Axle/23-27.html

 

John Davies

Spokane WA

[Raspy]

John,

 

I remember suggesting that your grabby brakes could be caused by grease on the lining. IIRC, you fixed that by cleaning the linings. Did you replace those shoes, and if so, did you replace all of them, or just the one that was grabbing? Could it be that some shoes have more friction than others if they are not the same material, or not as grease free?

 

Interesting how grease makes a shoe grab harder.

 

My brakes were very weak in the beginning. They would not skid on the maximum setting. Now, I'm down to about setting 4 and they are working fine. I'm sure they are holding evenly because I feel no left or right pull.

 

Next time you are in there, it might be interesting to switch the magnets between the hot brake and the cold brake and be sure no grease is on the magnet friction area. The magnets might become grabby too, or just slip and not hold much.

[John E Davies]

John,

I remember suggesting that your grabby brakes could be caused by grease on the lining. IIRC, you fixed that by cleaning the linings. Did you replace those shoes, and if so, did you replace all of them, or just the one that was grabbing? Could it be that some shoes have more friction than others if they are not the same material, or not as grease free?

Interesting how grease makes a shoe grab harder.

My brakes were very weak in the beginning. They would not skid on the maximum setting. Now, I’m down to about setting 4 and they are working fine. I’m sure they are holding evenly because I feel no left or right pull.

Next time you are in there, it might be interesting to switch the magnets between the hot brake and the cold brake and be sure no grease is on the magnet friction area. The magnets might become grabby too, or just slip and not hold much.

 

Very good comments, I never replaced any linings. It is possible that the left shoes are contaminated due to the (small) grease leak I previously had. You cannot swap magnets (or shoes) side to side since they are L/R specific due to the shape of the swinging arm they are riveted to.

 

The one grabby brake works fine most of the time, it only gets grabby when it heats up. So I don’t see how contaminated linings could be doing that. But maybe so....

 

I have complained before about Dexter price fixing, it makes no sense to buy individual parts like shoes when you can buy the entire assemblies at 60% off MSRP. The parts are not seriously discounted and no shops stock them anyway... they all just swap out the assembled backing plates.

 

John Davies

Spokane WA

[Rleog]

John

 

Thanks for taking the time to comprehensively document this potential problem. I don't think that I have this problem because the trailer seems to be braking evenly. I'll be doing the 6000 K bearing service soon and will then have a close look at the brake assemblies and wiring.

 

If my brake controller wires are the same as yours I'll likely change them out also, following your well illustrated examples.

 

Bob G.

[John E Davies]

John

Thanks for taking the time to comprehensively document this potential problem. I don’t think that I have this problem because the trailer seems to be braking evenly. I’ll be doing the 6000 K bearing service soon and will then have a close look at the brake assemblies and wiring.

If my brake controller wires are the same as yours I’ll likely change them out also, following your well illustrated examples.

Bob G.

 

Thanks for the kind comment.

 

I want to strongly emphasize that you can’t tell by how the trailer is acting if one or more of the brakes are working unevenly. Even if my one grabby brake locks up hard on pavement, smoking and flat spotting the tire, the trailer stays straight and true. Only by stressing them on a steep descent and then measuring the temps can you truly know how they are working. A TPMS that shows temp will not be accurate or have a quick enough response to do this. It might just show the TIRE as running slightly warm. We need to focus on the drum temps.

 

I hope a number of owners will do this and check in here. I expect this is not unusual, just under reported!

 

These temp guns were once well over $150. Now they are so very cheap it makes sense to have one in your glovebox or map pocket for quick checks on the road. ...https://smile.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=Laser+temp+gun

 

I actually have two, one in my shop that years ago cost $80, and one that I carry, the latter was free from Harbor Freight during a promotion. It is poor quality but functionally the two are identical. If you buy a cheap one and it eventually quits, toss it and get another.....

 

John Davies

 

Spokane WA

[Rleog]

Thanks again.

Just ordered a temp gun.

Bob

[John E Davies]

Another reason to move your wires outside the axle tubes.....

Common Reason for Shorting Trailer Brakes - Electric Trailer Brakes - Check Your Axle Wires

John Davies

Spokane WA

[JRK]

I understand that the size of the wire, if too small, would cause resistive heating in the wiring and possibly melting of the insulation and/or a fire. Is it the restricted amperage due to the wire size that possibly causes the improper operation of the brakes?  Changing the external wiring along the axle might help increase amperage flow along those wires, but I assume that there remains 18 gauge wiring in the hull, which restricts the amperage (current) flow, so changing the external wiring really does nothing to improve current flow to the brakes. Which also creates an overheating hazard inside the hull due to resistive heating of the wiring. So OIiver has delivered a dangerous, hazardous condition not only for brake operation but also a fire hazard-only when the brakes are operating? To correct the problem, the wiring from the 7-pin connector to the brakes needs to be changed to probaly a 10 gauge stranded wire, depending upon length of run (according to nec chart)? Definitely 18 gauge is too small to handle 3 amps.

[Geronimo John]

On 3/14/2021 at 5:26 PM, JRK said:

 To correct the problem, the wiring from the 7-pin connector to the brakes needs to be changed to probably a 10 gauge stranded wire, depending upon length of run (according to NEC chart)? Definitely 18 gauge is too small to handle 3 amps.

@JRK:

I share most your thoughts.   Some more pondering on my part is in order for the below:  

• I am wondering how the brake controllers wires for millions of brake controllers, from the drivers position all the way back to the rear RV axles, are handling the max braking events?  None of my many TV's and Trailers I have owned have had mega sized cables as suggested.  I suspect this is the case for lots of reasons.   In our case, my first one is that the max amp pull of 12  amps  (3 amps X 4 brakes) is rarely a  long duration continuous load.  Secondly, modern brake controllers sense when a vehicle is stopped and back off the power flow to the magnetic coils when stopped, again shortening the duration.  As such, maybe these ideas contribute to having used smaller wires for many many decades in millions of TV's.

• Using commonly used American Wire Gauge Cable/Conductor Sizes and Properties as a guide is not commonly practiced for short runs such as a TV and Ollie.  For example, it lists a #12 AWG  wire (assumed to be copper) as only carrying 9.3 amps.  Where as they are allowed a continuous use rating in residential of 16 amps, and 20 amps intermittently.  Hence they are protected by a 20 amp breaker.  A #10 conductor is listed with a max current of 15 amps.  Yet our Oliver, and about a million other similar trailers use these as 30 amp conductors and breakers.   My experience as an engineer suggests that 14 ga would be a sufficient choice.  However, your 10 ga would certainly work!  Overkill, but it will work great!

All that said, when it comes time to replace my brake assemblies, I'll certainly upgrade the wiring, not to 10 ga, but for sure larger than that which Oliver used.  And as JD pointed out, it will not be run inside the axle.  

Finally, and it is a very rare occasion that I have ever suggested taken a JD suggestion even further.  But here I go into unchartered regions....., My recommendation is to also run the larger replacement wires through a gray plastic (UV Resistant) conduit (Maybe 3/8") across the back side of the axle.  Where the cable inters and exits the pvc, I will heat shrink wrap the cable with a 4" section (2" inside and 2" outside the PVC), and seal both ends of the conduit with a suitable Silicon sealant.  These extra precautions are to protect the line from physical road damage, hungry rats. 

BONUS SUGGESTION:  Spray all exposed wired outside the hull (IE under the hull, in the front basket, and for the cables going to the TV) with peppermint oil and water solution.  Most wire insulation eating critters (Mostly rats and mice) hate peppermint.   It is also useful to spray tires, and jacks to dissuade those critters.  

I look forward to your and our owners thoughts. 

Thanks,   Geronimo John 

[JRK]

I don't think that it is actually 12 amps - it is 3 amps spread across the 4 brakes, which is partly why they are grabbing for JD, especially if only 2 amps is allowed to pass. I am not sure how they are wired, parallel or series. It would be nice to have a real wiring diagram that should show proper size wire and how they are wired.

[Geronimo John]

According to E-trailer, they state in their "How much power do electric brakes use?" the following:

While there is no absolute standard for amp requirements on trailer brakes there are common practices between trailer component manufacturers. This creates a defacto standard. We’ve determined amperage requirements based on extensive testing, customer experience and information gathered directly from trailer component manufacturers. We’ve found the most common amperage draw on a 7-inch brake magnet to be 3.2 amps maximum.  The increased amperage of a 10 or 12-inch brake magnet tends to max out at 4 amps. This means that a double axle brake system would be drawing a maximum of 16 amps for a full emergency stop.

So, I'm thinking that when replacement or repair time comes around, that AWG 14 is likely to be a reasonable choice.

Your thoughts?  

GJ

[John E Davies]

On 3/18/2021 at 4:42 PM, JRK said:

I don't think that it is actually 12 amps - it is 3 amps spread across the 4 brakes

Reposting a pic from the top of the thread.... This is the DC amperage current draw for the entire four brake system, measured at the breakaway switch, with four AGM batteries and no shore power connection, with the BAS switch plunger pulled. (With lithium batteries the current will be a little lower). They are wired in parallel, which is why you see this number -  the individual magnet draws of (about) 3 amps each add up.

Your brake controller may only be applying 3 amps to all four, depending on how you have it adjusted and the trailer weight, but that is a different matter entirely. Many controllers don't show current, The Tekonsha P3 shows voltage. My (really) old Jordan Ultima 2020 mechanical unit (rheostat with a bicycle-type steel cable that attached to the brake pedal) showed only amps.

If you have a P3, you can go into the Troubleshooting menu and get to an ammeter, it shows actual current going through the blue control wire, but this has nothing to do with the full amperage "panic stop" when the BAS is operating:

John Davies

Spokane WA

Edited March 23, 2021 by John E Davies

[Geronimo John]

On 3/18/2021 at 1:42 PM, JRK said:

I don't think that it is actually 12 amps - it is 3 amps spread across the 4 brakes, which is partly why they are grabbing for JD, especially if only 2 amps is allowed to pass. I am not sure how they are wired, parallel or series. It would be nice to have a real wiring diagram that should show proper size wire and how they are wired.

@JRK:  Here is the Dexter chart that reflects what I thought concerning amperage to their dual axle brakes:

[Geronimo John]

On the other hand, here is the Dexter AWG wire sizes chart.  With an OEII, we would be on the 4 brakes, under 30 feet  =  12 AWG.

So the text book answer is 12 AWG.  But I still think that 14 AWG would work very well.  That said, when my time comes to replace the cable.... I'll ponder it a bit more.  🙂

For those wanting the full Dexter Service info, it may be found at:  

     http://www.dexterpartsonline.com/files/2036913/uploaded/600-8K Complete Service Manual.pdf

GJ

Edited March 24, 2021 by Geronimo John

[Rivernerd]

Seems clear to me from review of this thread that, to be consistent with Dexter's specs, Oliver should now be using 12 AWG CU wire for Elite II electric brakes, since there are 4 brakes.  Thanks to those who have posted here for figuring this out!

Does anyone know if Oliver has upgraded the wire gauge for the Elite II electric brakes from the 18 and 20-gauge conductors John Davies noted three years ago, at the beginning of this thread ?   I'd like to be assured that when my Elite II is built next year, Oliver's manufacturing methods comply with their supplier's specs, and that my trailer brakes will function as designed.