Downhill Brake Controller Zeroing Out

[RVtrek]

So I've started towing my trailer around, and for the most part, everything is working exactly like it should.  The only exception seems to be if I'm going very slow down a snow-covered hill.  Under that situation (this is around 10mph or less) and I need to stop or slow down greatly when going down the hill, the brakes on the trailer will cut out, the voltage on the brake controller will show zero, and then after a portion of a second, the brakes will kick back on.

When I'm traveling on the highway and need to use the brakes, they're working fine.  If I'm on side streets and using the brakes, they work correctly.  In fact, they work really well, I can hardly tell I'm stopping twice as much weight, the truck just really doesn't feel any different.

It's only when I'm going down a snowy hill at low speed and using lots of brake pedal pressure does this situation occur.  It *almost* feels like it's an ABS type of thing kicking in.  I'm pretty sure the trailer wheels are locking up given the amount of brake pressure and the snow covered hill, so is my controller trying to help the tires regain traction or something?

Other than this issue, everything else mechanically has been working out great with towing the trailer.  Any ideas?

 

[highdesertranger]

what type of brake controller? make an model? highdesertranger

 

[wayne49]

Sounds like the circuit breaker popping under heavy continuous load then resetting.

Maybe adjust the brake controller to not so heavy.

 

[RVtrek]

what type of brake controller?   make an model?  highdesertranger

Tekonsha 90195 P3 Electronic Brake Control, amazon link.

 

[RVtrek]

Sounds like the circuit breaker popping under heavy continuous load then resetting.

Maybe adjust the brake controller to not so heavy.

I didn't even know there were circuit breakers in my truck!  Relays and fuses, sure, but I've never heard of a circuit breaker.  Handy that it resets itself!

I certainly could adjust the voltage down on the brake controller, but I feel like it's pretty well dialed in to where it needs to be to help me stop the rig.  (I think I have it set at a max of 7.0 or 7.5 volts right now.)

If the circuit breaker is resetting, maybe because the amperage draw is too high?  The truck's wiring system is old, and, well, kinda crappy (but it does all work).  I'm wondering if a new set of wires from the engine bay all the way to the 7 pin wiring harness would take care of it?

 

[tbair]

Tekonsha 90195 P3 Electronic Brake Control, amazon link.

I was curious about trailer brakes (I have truck camper so I have not experienced them) so I read the manual. Then manual does mention that it has an inertial sensor which might be what is causing the problem? It does detect at least some voltage and amp problems so that may not be the issue. Again I know nothing other than the manual.

 

[RVtrek]

I was curious about trailer brakes (I have truck camper so I have not experienced them) so I read the manual. Then manual does mention that it has an inertial sensor which might be what is causing the problem? It does detect at least some voltage and amp problems so that may not be the issue. Again I know nothing other than the manual.

I don't *think* it's the inertia sensor that's causing the brakes to drop to zero.  Their voltage is relatively high (>3) when the drop happens, and the whole rig is still moving at the time.  I'm not sure what the exact voltage is, I'm usually looking at my environment instead of the voltage when in that situation.

 

[jimindenver]

Try the same situation but manually active the trailer brakes and see if it does the same. Also do the brakes cut out when you are holding the rig say at a stop light?

 

[RVtrek]

Try the same situation but manually active the trailer brakes and see if it does the same. Also do the brakes cut out when you are holding the rig say at a stop light?

I'll try to remember to manually activate the brakes next time I'm in that situation.  Interesting to see what it does.  I'll also play around with just manually applying the brake while stopped and see how it responds.  Of course, my trailer is in storage now for about a week until my next adventure, so this will all have to wait a bit.

When holding at a stop light, the brakes do not go out.  However, I don't sit with my foot pressed as hard as I can on the pedal when stopped at a light either, I'm generally pressing pretty lightly.  The voltage at stop lights ranges from 0.6v to ~1.3v.

 

[wayne49]

You said this happens on downhill run? Any downgrade or a longer and/or steeper grade?

Do you use engine braking by down shifting going downhill? That helps save the vehicle brakes and the trailer brakes.

The circuit breaker is somewhere between the output of the controller and the 7 pin connector. Only the person who installed the controller would know where that is exactly.

Do not replace with a larger amperage CB.

-Wayne

 

[Every Road Leads Home]

Hi RVTrek,

No advice for you on the brake control issue, but just wanted to say what a great looking trailer. Read some of your blog and am now considering a Becker trailer as well. Though I had figured out what company I was using, but now will seriously be looking into these.

 

[RVtrek]

You said this happens on downhill run? Any downgrade or a longer and/or steeper grade?

Do you use engine braking by down shifting going downhill? That helps save the vehicle brakes and the trailer brakes.

The circuit breaker is somewhere between the output of the controller and the 7 pin connector. Only the person who installed the controller would know where that is exactly.

Do not replace with a larger amperage CB.

-Wayne

This has only happened twice (I've had the rig for a very short time).  It happens when going down a step enough grade that brakes are needed, but it's very short, and we're talking about speeds under 20mph and I want to slowly come to a stop.  I haven't had to try any mountain passes yet.

The hills aren't big enough, long enough, or running at a high enough speed to warrant engine braking.

I'm thinking I'll do some more testing, and if it continues to trip the breaker, I'll upgrade the wiring to something a bit thicker with less splices in it.  I know my current wiring is a bit of a hack job because it had to be repaired at least once.

 

[highdesertranger]

anytime your braking is a good time to downshift. if you had a stick shift wouldn't you down shift? as far as the controller, I am sure you have gone over all of the manual and checked everything twice. have you tried to contact the manufacturer? highdesertranger

 

[RVtrek]

anytime your braking is a good time to downshift.  if you had a stick shift wouldn't you down shift?  as far as the controller,  I am sure you have gone over all of the manual and checked everything twice.  have you tried to contact the manufacturer?  highdesertranger

If I'm going down a mountain, I'll downshift.  The truck already had overdrive shut off, and I was only going about 10 mph or so, so if I just push on the brakes on the truck it would have stopped the whole rig, regardless of what the trailer was doing.  I was just noticing this zero-ing out behavior in these conditions.

My next step is to do some diagnostic tests with the rig once I get a chance to.  Right now the trailer is at my storage facility and I won't be seeing it again until sometime next week.  The city I live in doesn't allow on-street overnight parking, and since I'm in a townhouse right now, there's no room in the "driveway" to keep it at the house.

And yes, I checked the manual, thoroughly.  No mention of this concept in it at all.

If after the diagnosis work (and probably some fresh wiring), if it's still happening then I'll contact the manufacturer.  Generally by the time I need to contact tech support I already know what the issue is, what the solution is, and I just have to walk through the process with them.

 

[closeanuf]

Did you buy and install the adapter from the maker of the controller or was it wired in the "old fashioned" way?
Just something else to consider.

 

[RVtrek]

Did you buy and install the adapter from the maker of the controller or was it wired in the "old fashioned" way?
Just something else to consider.

I purchased a vehicle-specific wiring harness for the brake controller from the same company that makes the controller.  I'm not concerned about that side of the wiring.  It's the wires going underneath the truck from the engine back to the trailer that I'm more concerned about.  This might turn into a RTR project.

 

[RVtrek]

BTW, I think I've figured this out.

If I'm pressing on the brake pedal, but start to release some pressure on the pedal, the controller will immediately go to 0 volts.  This occurs even if I'm still slowing down and am technically still applying the brakes.  As soon as I reduce my pressure on the brake pedal, it goes to 0.

I tried other tests where I do not release pedal pressure, and the brake controller will continue to apply voltage as needed.  I've also tried manually applying voltage all the way up to it's maximum output, and holding it there, and it complies with those tests.

Now that I'm aware of this behavior, I know what to expect.  Basically, the controller is expecting me to never partially release the pedal.  I should either release it, or hold it steady (or press harder).  With that information, braking hasn't been an issue.

 

[highdesertranger]

thanks for the follow up Michael, good info to know. highdesertranger