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jazzbone · 08-04-2002, 12:23 PM

My family is just trying to leave on vacation today and the brakes on our airstream aren't working. The truck brakes work and there is the usual hum like the brakes are working and the brake lights go on, but my dad says the brakes aren't engaging on the trailer.
Also is it dangerous to drive without brakes on the trailer on fairly flat road?
any help would be appreciated

sudden impact · 08-04-2002, 01:02 PM

i have,but you want to be xtra carefull. i towed my a/s from charlston, s.c which is about 250 miles from my house. but i was towing with a 1 ton truck,so braking was'nt a problem,just allow double the stopping distance. but if you have the time i would try too find out the problem

uwe · 08-04-2002, 05:01 PM

I would not go out on a vacation without the brakes on my Airstream, I also tow with a 1 ton vehicle. It is absolutely unsafe. Have the brakes fixed, or check the brake controller adjustment.
If the magnets are humming, then probably you need adjustments on the brake controller.
Read the manufacturer's instructions, and try again. Chances are it's something simple.
Don't have your vacation ruined by an accident because of the trailer brakes.

**Action** · 08-06-2002, 12:45 PM

The brake lites and the brakes themselves are on seperate circuits. So do not rely on the brake lites as an indication that the brakes work.

It is also possible that you have a mechanical issue. You may want to pull a wheel to check things over especially if it has been some time (more than a year) since you have checked in there.

>>>>>>>>>>>Action

**jcanavera** · 08-06-2002, 01:54 PM

Just curious, if he hears the hum, how is he determining that the brakes aren't working?

One thing I would do to test is to activate the manual braking function from my brake controller (without stepping on the vehicle brakes) and see if I encounter resistance. If there is a proper amount of resistance, then the brakes are getting power from the controller.

Assuming you have braking at this point, a second check would be to verify if the brake controler's level switch and gain switch are properly adjusted.( I am also assuming you have a traditional pendulim based controller). Normally you get your tow vehicle and trailer on level ground, step on the brake and adjust the level knob until your controller justs shows minimal activation of the trailer brakes. At that point you can drive slowly and apply your vehicle brakes while turning the gain knob. This will give you the amount of braking that you deem proper for effective stopping of your trailer. Too much gain and your trailer wheels lock up, to little and the tow vehicle is not getting the assistance necessary from the trailer brakes.

You could have a completely different problem but a maladjusted controller can give you symptoms of no brakes. I hope your problem is in this area.

Jack

Pahaska · 08-06-2002, 02:43 PM

Electric brakes are servoed. The drag of the magnet rotates the shoes outward to drag againstthe drum. The wheel must turn some degrees before the brakes wll take effect.

Why would you hear a hum? The brakes are DC activated and there is absolutely no reason for there to be a hum. There is usually a soft clank of magnet against drum when current is applied and that is all the noise there should be with the trailer stationary.

**jcanavera** · 08-06-2002, 03:19 PM

Quote:

Originally posted by Pahaska
Why would you hear a hum? The brakes are DC activated and there is absolutely no reason for there to be a hum. There is usually a soft clank of magnet against drum when current is applied and that is all the noise there should be with the trailer stationary.

John I'm not an electric person but I've had three different trailers and all have exibited a hum (albeit very low pitched) when the brakes were engaged. You just get your ear down by the wheel and you can hear the hum when power is flowing to the brakes.....unless less that buzz is from something else

Jack

Pahaska · 08-06-2002, 05:11 PM

I never heard a hum, although my hearing is not the best courtesy of being an F86D instructor years ago.

I have a little test rig that I built some years ago when I was having some brake problems with my Scamp. It is a truck-end socket with a toggle switch that wraps the charge line which is hot from the battery to the brake line. When I turned on the juice, I always heard a clunk from the magnets , but that was all. If I turned the switch off and on again, there was usually no repeat sound because the magnets were still against the drum.

The hum makes me wonder whether some controllers vary the braking force by chopping the 12v. There really shouldn't be a hum unless the voltage is changing, either AC (and we know it's not AC) or possibly chopped DC.

jazzbone · 08-11-2002, 06:13 PM

Thanks everyone for the feedback. My dad (who is a very careful driver) took it all the way to big sur and back (to Santa Barbara), without any problems. We saw a mechanic and he said everything was fine. I think the problem is that the brakes aren't adjusted properly, (they're too light). I think we can fix it ok though.

**Action** · 08-11-2002, 06:22 PM

Jazzbone,

It is possible to adjust the brakes with a wheel jacked up off the ground (from the inside of the backing plate) however I would recommed that you remove a wheel and drum assembly to check everything else too. Then reinstall the brake drum and spin to see if the shoes barely touch the drum. If not remove the drum and adjust the star wheel on the bottom that spreads the shoes apart.

And if you have disc bakes there is no adjustment so ignor the above.

>>>>>>>>>>>>>Action

smily · 08-21-2002, 09:24 AM

Okay,
I am in Brake mode while I await the curtains to be finished.....

Question: Are the brakes supposed to humm all of the time?

I just installed the new brake controller and a new 7 way connector on my Dodge Ram 1500.

Then I ran a hot wire from the Brake controller to the seven way connector and a hot wire from the battery to the 7 way connector.

Obviously the wire from the Brake controller is for the brakes and the hot wire from the battery is for charging the trailer battery.

First, I checked all of the lights to include Brake, running, and side markers. All are good. Brake lights come on when the brake pedal is pressed.

After connecting the seven way connector to the trailer, I walked to the wheels of the trailer and I heard an obvious Humming from the wheels. (I have not pressed the Brake pedal yet).

At first I consider that the wires may be reversed at the seven way connector, (hot and Brake wire), so I disengage the "hot wire" from the battery and the humming at the wheels stopped.

I asked my eight year old son to press the brake pedal and I can hear a soft "clank" at the curb side wheel well, no noise from the street side. I do not hear any humming from either side of the trailer.

I have a adapater cable that came with trailer. The adapter converts from round pins on A/S to 7 flat pins.

I am going to check wiring through adapter and compare to PDF from A/S .com to confirm wiring.

I am wondering, should I hear a "humm" from the wheels all of the time or just when the brake pedal is pressed.

Smily

thenewkid64 · 08-21-2002, 10:10 AM

Smily,

Have you checked the function of your breakaway switch. There should be a pin and cable switch on the tounge of your trailer that engages the brakes when the the pin is pulled. If this switch has become corroded, you may have voltage leaking thru it. This could account for the hum. The clue here is the fact that disconnecting the 12 VDC feed for the battey stops the hum. The breakaway switch uses the 12 volt feed from the coach battery to engage the "emeregency brakes" thru the breakaway switch.

Do you have a battery installed in the coach? You could disconnect(Cut wires) to the breakaway switch and see if you have working brakes with no hum while all 7 wires are connected.

If there is no switch, you may want to see if there are some wires on the tounge that have been spliced together. They may be remmnants and could also be part of the problem.

You should hear the soft clunk on both sides. The concern I would have if only one side is working is that the trailer would want to pull to one side as you stop, so check the connections behind the wheel on the side that is not clunking when the pedal is depressed. There are two wires from the coach and from the wheel each should be connected induvidually and the is no polarity.

Let us know what you find.

**jcanavera** · 08-21-2002, 10:14 AM

Quote:

Originally posted by smily
Okay,
I am in Brake mode while I await the curtains to be finished.....

Question: Are the brakes supposed to humm all of the time?

I am wondering, should I hear a "humm" from the wheels all of the time or just when the brake pedal is pressed.

Smily

Smily,
This was an observation that I have noticed but I only hear the hum when the brakes are on. Also note that the hum I hear is very faint and I have to get my ear down by the wheel to pick it up. Others on the list haven't heard that hum. I wouldn't be concerned if you can't hear that. The key is that the brakes are engaged and you did hear the "clank" so don't get concerned. Of course you do need to hear the other side engage also. I guess I'm lucky since I clank and hum.

Jack

LeeC · 08-21-2002, 10:33 AM

You might hear a slight hum from the wheels when the brakes are activated but should not hear any hum when the brakes are not activated.

smily · 08-21-2002, 10:54 AM

Folks,
The Humm is loud! I can hear it from the tow vehicle. It is not deafining but considering the feed back, the humm is loud.

I forgot to mention in my previous reply post that my break away switch is already "cut". There are two wires hanging from the break away switch but I do not see any wires that they were previosly connected to. These wires were already cut when I bought the trailer.

So, as to bleed through current, I am not certain. Will the brakes work without the breakaway switch? I will fix another day.

Where does the Breakaway switch hook up to?

I do have a single conductor hanging from the adapter cable that I referred to in my previous post. I assumed that it may go to an electric jack, (if it ever had one or for future). Any way this conductor is single and it is about 14 -12 AWG.

Can I see wire to brakes from rear of wheel without removing wheel? I have tandem axles. I will look for disconnected wires but The humming leads me to believe that wire is connected.

Although, I did not notice the continuity LED illuminte on my brake controller. ( Brake controller has continuity LED, Escort Brand)

Standing by for update,
Thanks,
Smily

smily · 08-21-2002, 11:08 AM

Oh! New kid,

When I referred to disconnecting hot wire and Humm stopped, I was referring to the Tow vehicle battery.

I did not disconnect the trailer battery.

Although there is a switch from my Univolt to my Trailer battery, (came with the trailer) the switch acts as a "disconnect between the battery and the Univolt.

I suspect that this switch was added on after manufacture.

Any way this "Disconnect" was open at the time of the testing and the humm. I leave this disconnect switch in the open position when I am using 110 volts in the trailer because I read that a Univolt can "cook" a battery if left on all of the time. Is this correct?

I can check the brakes again with the trailer battery engaged. Maybe there was a problem between the Univolt and the voltage applied through the seven way connector.????????

I am shooting in the dark and reaching for the sky...........

Smily

Pahaska · 08-21-2002, 11:17 AM

The loud hum means that you probably have the full 12v to the brake magnets. I, too, would be concerned with the breakaway switch since that switch, by nature, puts the full voltage on the magnets. If not the breakaway switch, I would look for a short from the charge circuit to the brakes.

Do you have a trailer battery? Sounds like you may not have one. If you have a trailer battery, disconnect it. Then disconnect the 12v charge wire, turn on a light switch in the trailer, and have someone see if the light comes on when you step on the brake pedal (or better yet put full voltage on the brakes with the panic lever on the brake controller). If the light comes on, then the brake circuit is shorted to the 12v charge circuit somewhere.

BTW: If you don't have a breakaway switch, you should have one. State laws vary, but most every state requires breakaway switches on trailers of Airstream size.

smily · 08-21-2002, 12:17 PM

I do have battery in trailer. I have a "disconnect" in the rear compartment. I use this disconnect to isolate the battery from the Univolt to prevent overcharging of the battery.

I read somewhere that a Univolt can overcharge and "dry" the battery out if left hooked to 110 volts for long periods. I leave my trailer hooked up to 110 volts while in the driveway at the house.

I agree that the Break away switch is crucial to safe operation but I merely trying to isolate and correct the brake problems at this time.

Once I figure out where the breakaway switch is supposed to hook to, I will splice the wires that are currently hanging from the Break away switch to their respective mates.

Any idea where the "mates" are to be found. I did not notice anything obvious. I will look under the trailer today.

Thanks for the help,
Smily

Pahaska · 08-21-2002, 12:39 PM

I can only tell you where it is connected on my trailer, but I suspect all AS are going to be the same in that respect.

The breakaway switch is connected inside the front center of the trailer shell on the floor. One leg of the breakaway is shown attached to the blue brake wire, the other goes through a 20A Type 2 breaker to a terminal block that is fed from the battery. This does not go through the disconnect.

The charge line attaches to the adjacent terminal on the terminal block. The line from the breakaway switch to the breaker/terminal block is labled as "blue".

thenewkid64 · 08-21-2002, 12:43 PM

Smily,

I think you just gave me a clue. The beakaway switch is a normally closed switch. Meaning when the pin is pulled it closes, the pin holds it open. If the two wires that come from the frame are connected together you have activated the "emergencey brake" system. There should be 2 wires off the switch and 2 wires on the frame rail. One wire from the breakaway switch should go to one wire off the frame rail. Polarity is not an issue.

If the two wires on the frame rail are connected, disconnect them from each other. This should stop the brake hum.

As to the disconnect switch on the univolt, does it disconnect the battery entirely from the trailer or just stopthe univolt hum?