Jump to content
Sign in to follow this  
John E Davies

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

Recommended Posts

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:

 

IMG_5343.thumb.jpg.11673f14dc9b3a80959e6be097f9ce66.jpg

 

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:

 

IMG_5333.thumb.jpg.5f54be817b5185d90d2f91ccce4f5e4b.jpg

 

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:

 

IMG_5338.thumb.jpg.bd83295ff119da9f68991c8b13f2de96.jpg

 

Left front:

 

IMG_5340.thumb.jpg.36f1dbfa27b047dfc9a59759cf6d2116.jpg

 

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:

 

IMG_5342.thumb.jpg.f3395e35b2fe9dabebc413311661e920.jpg

 

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.

 

IMG_5345.thumb.jpg.4b9ebe783be772218f65416b1c47a6d1.jpg

 

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:

 

IMG_5348.thumb.jpg.00f33229b65b83ea69023d4110847cdf.jpg

 

The left side splices, where the feed wires join:

 

IMG_5349.thumb.jpg.b9f6fb474bf5d18b0f6dfd2f114ee8c5.jpg

 

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

 

IMG_5350.thumb.jpg.ab850a671699f63705e03c88f2b7d55e.jpg

 

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

 

IMG_5346.thumb.jpg.5563926c87c97d32c52ceef87eab80b6.jpg

 

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

 

IMG_5347.thumb.jpg.fca5321100ac1786f4675ecacd2b0959.jpg

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dexter-electric-brake-wire-guidelines.png.af3628fba8279540586fb5affa8b02a3.png


"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

 

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

Share this post


Link to post
Share on other sites

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


"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

 

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

Share this post


Link to post
Share on other sites

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


"I only exaggerate enough to compensate for being taken with a grain of salt."


LE2 #92 (sold),   Black Series HQ19   

Share this post


Link to post
Share on other sites
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


"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

 

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

Share this post


Link to post
Share on other sites

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 1

Bob G

Share this post


Link to post
Share on other sites
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


"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

 

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...