Visit our Popular Forums

timmaah · 05-23-2013, 05:00 PM

I am trying to troubleshoot why my brakes seem to only work at about half of desired force. This is on a 1999 25' Safari.

I can't get the brakes to lock up at all, even with the controller cranked up to 13. The trailer brakes will slow the airstream down fairly well, but they don't lock up. (This is on loose dirt/gravel)

I thought it might have been the brakes were worn, so I replaced all 4 including new drums. This does not seem to make a difference. I have the brakes adjusted pretty tight. They were scraping when turned.

Voltage readings taken at all four wheels before installing new running gear showed about a volt less than the controller output. The magnets all grabbed the wheel and I am unable to turn by hand.

There is a junction box on the tongue. (I think someone lengthened the 7 pin cable) and there it also reads 1 volt less than the controller. Never above 11 volts. And it falls as well. Holding the controller level the volts at the tongue drop about a hundredth every second.

And if I pull the breakaway cable the volts read 11 and I couldn't get them to lock up.

Any thoughts? Bad ground somewhere? but where?

We are heading into the hills of Colorado very shortly, so I want these suckers working correctly, not at 50%.

robert claus · 05-23-2013, 05:19 PM

Check the power on the supplyside to the controller from the battery. It should be about the same as between the battery posts. If not, check the gauge of the wire to the controller (that it isn't too light) and clean the in line fuse and holder that should be there.

timmaah · 05-23-2013, 06:14 PM

Quote:

Originally Posted by robert claus

Check the power on the supplyside to the controller from the battery. It should be about the same as between the battery posts. If not, check the gauge of the wire to the controller (that it isn't too light) and clean the in line fuse and holder that should be there.

The controller is a P3 hooked directly into the factory 2008 Tundra wiring. The diagnostics on the P3 say 12.3 volts and 12 amps. There is no dragging even with breakaway switch pulled, so I'm not sure it is a controller issue.

We just readjusted the brakes. Didn't take it for a spin, but even on dusty grassy surface and the controller on full (or break away switch pulled) the wheels still turn when pulled by the truck.

Bigventure · 05-23-2013, 07:37 PM

Who did the brakes? Could the shoes be backwards? There are fronts and rears.

timmaah · 05-23-2013, 07:52 PM

Quote:

Originally Posted by Bigventure

Who did the brakes? Could the shoes be backwards? There are fronts and rears.

That would be me. I put the left on the curb side. They matched what came off.

The problem is that there was no change. Even before changing the brakes I was having what I think are "problems". I have nothing to compare it to.

A W Warn · 05-23-2013, 08:09 PM

Check the wire connections for corrosion at the wire nuts behind the wheels.
Check where the ground wire attaches to the body to make sure it is not corroded.

I'll bet on the corroded ground.

dznf0g · 05-23-2013, 08:13 PM

Based on what has been said, I would look for high resistance in the trailer wiring. Corroded or poor connectors. In the past, rather than trying to find a culprit area in a trailer as vintage as yours, I'd just go ahead and run new wiring from the umbilical termination through a new breakaway switch back to the drum magnets. Otherwise I was always chasing my tail to the next bad connection. Many times you will find chaffed insulation in the old wiring as well. It's not hard...just time consuming. Also, as AW Warn says, physically remove the grounds and clean the area. Go back with a star washer to get a bite into the chassis.

timmaah · 05-23-2013, 08:14 PM

Quote:

Originally Posted by A W Warn

Check the wire connections for corrosion at the wire nuts behind the wheels.
Check where the ground wire attaches to the body to make sure it is not corroded.

I'll bet on the corroded ground.

On mine, both wires disappear into the frame. I'm not sure where they get grounded to.

When I had the magnets off I checked each wheel and they were all getting the same voltage and they aren't able to be turned by hand.

dznf0g · 05-23-2013, 08:20 PM

Voltage to the magnets, of near battery voltage is an indicator of decent supply voltage integrity. Use an ohmmeter to check resistance FROM the magnet to chassis ground. Anything much above zero indicates an ineffective ground. If you can't find the ground location....create a new one...no harm in that.

timmaah · 05-23-2013, 08:20 PM

Quote:

Originally Posted by dznf0g

Based on what has been said, I would look for high resistance in the trailer wiring. Corroded or poor connectors. In the past, rather than trying to find a culprit area in a trailer as vintage as yours, I'd just go ahead and run new wiring from the umbilical termination through a new breakaway switch back to the drum magnets. Otherwise I was always chasing my tail to the next bad connection. Many times you will find chaffed insulation in the old wiring as well. It's not hard...just time consuming. Also, as AW Warn says, physically remove the grounds and clean the area. Go back with a star washer to get a bite into the chassis.

How would I check for resistance? I was wondering if rewire would be a solution, but I'd like to pinpoint it as an issue before I do.

timmaah · 05-23-2013, 08:22 PM

Quote:

Originally Posted by dznf0g

Voltage to the magnets, of near battery voltage is an indicator of decent supply voltage integrity. Use an ohmmeter to check resistance FROM the magnet to chassis ground. Anything much above zero indicates an ineffective ground. If you can't find the ground location....create a new one...no harm in that.

Thanks. All the voltage at the magnets was the same as the tongue. A volt below what the P3 says.

I shall check the resistance tomorrow.

dznf0g · 05-23-2013, 08:29 PM

Are you saying that you only have 11.6 (ish) volts at the TV 7 pin connector? That seems low. You may have a high resistance issue in the TV brake wire......or a combination of issues.

timmaah · 05-23-2013, 08:36 PM

Quote:

Originally Posted by dznf0g

Are you saying that you only have 11.6 (ish) volts at the TV 7 pin connector? That seems low. You may have a high resistance issue in the TV brake wire......or a combination of issues.

Yes. That is tested at a junction box on the tongue. I'm not sure how to test in the TV as the controller doesn't work if the umbilical cord is not attached.

but yeah.. a combo of issues? heh. The break away switch pulled won't lock up the brakes and seems to provide only 11.x volts. Battery voltage is definitely higher.

dznf0g · 05-23-2013, 08:48 PM

Disconnect the controller output wire from the truck wire that runs to the rear connector. Run a long test wire out the truck door, connected to the controller output on one end and connect the other end directly to the junction box brake connection. Now check voltage at the magnet(s). If it is near battery voltage and controller output voltage you have eliminated the trailer chassis wiring as an issue. If I understand your wiring routing (it is different than mine), you will have routed the test wiring around the umbilical and the truck wiring (not sure where the breakaway is in relation to the umbilical and the junction box). Now, if you have near batt voltage at the magnets, individually test resistance with your ohmmeter: 1) the breakaway switch with both ends disconnected from the harness 2) the umbilical brake pin to the disconnected corresponding umbilical brake wire end, and 3) use the long bypass wire connected to the disconnected TV brake wire at the controller end all the way back to the TV umbilical connector pin. If any of these have more than .5 ohm or more, I think you will have isolated your problem. Hope this make sense.

timmaah · 05-23-2013, 08:56 PM

Thanks Rich..

Makes perfect sense.
Now to find some time for even more troubleshooting.

idroba · 05-23-2013, 09:33 PM

Rather than checking voltage, or resistance, the easiest thing to do is to check the current the magnets take. Find the + 12 volt pin on the 7 wire trailer plug. Find the brake wire on the plug. Put an ammeter between those two wires. Properly operating wiring should result in 2.5 to 3 amps per wheel, or 10 to 12 amps total for a 4 wheel setup. If you are not getting that reading there is some electrical issue to deal with, from corroded wires to poor grounds. If you read the full current, then there is probably something wrong with the brake setup itself (shoes, adjustment etc.)

Bob Thompson · 05-23-2013, 10:32 PM

In Post #5 Tim said he put the "lefts on the curb side".........aren't lefts supposed to be on the driver side?

timmaah · 05-23-2013, 11:02 PM

Quote:

Originally Posted by Bob Thompson

In Post #5 Tim said he put the "lefts on the curb side".........aren't lefts supposed to be on the driver side?

Ugg yes you are correct.. You'd think a grown man could keep them straight.

I put the lefts on the driver side / street side. The arm the magnet is attached to is facing forward.

My post 5 i stated it wrong.

cwf · 05-23-2013, 11:40 PM

One thing that must happen.. you must get brakes warm enough to transfer brake material from pads to drum/disc. So, on all my vehicles, I do some 'power' stops to 'set in' the brakes. They last a long time, rarely squeal and when they do, I repeat the heavy braking and get them hot..

Usually 3 brake applies from 60 to about 10 MPH... then let cool a bit... say for a couple of miles at 60, then repeat... do this for 4 cycles.. let brakes cool down as you drive and slow normally...

Now, test as you did before...