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Old 06-07-2010, 09:13 PM   #1
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Electric Brake issue /voltage

I am working on adjusting the brakes as well as a lot of other things. I have adjusted the brakes by crawling my big @ss under the Stream. I have adjusted them until they begin to lock and then back off a few clicks. After this was complete I expected the brakes to lock up when manually triggered by the brake controller slider.

Well you guessed it! They did not, I only noticed slight difference. I have inspected the pads and magnets and all look fine. I tested for voltage at the tow connector and voltage was 12.5 when applied without the plug, however when applied with the trailer plugged in i only recieve 7.5-8 volts with the manual override. I recieve the same voltage at the trailer wires.

Also, i disconected the TV and pulled the emergency pin and no locking. I also have re soldered all the brake connections and put heat shrink on everything.


Any ideas? I am stumped.

TIA
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Old 06-07-2010, 10:25 PM   #2
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Which brake controller are you using?
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Old 06-07-2010, 11:01 PM   #3
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Originally Posted by ck21084 View Post
I am working on adjusting the brakes as well as a lot of other things. I have adjusted the brakes by crawling my big @ss under the Stream. I have adjusted them until they begin to lock and then back off a few clicks. After this was complete I expected the brakes to lock up when manually triggered by the brake controller slider.

Well you guessed it! They did not, I only noticed slight difference. I have inspected the pads and magnets and all look fine. I tested for voltage at the tow connector and voltage was 12.5 when applied without the plug, however when applied with the trailer plugged in i only recieve 7.5-8 volts with the manual override. I recieve the same voltage at the trailer wires.

Also, i disconected the TV and pulled the emergency pin and no locking. I also have re soldered all the brake connections and put heat shrink on everything.


Any ideas? I am stumped.

TIA
It's not uncommon with electric brakes, to have "glazed" lining and/or drums.

Scuff up the linings, and then scuff up the brake drums and the armature plate.

But, it also sounds like you have a wiring problem on the tow vehicle.

Or, you can have one magnet that is shorted out internally. Check the resistance in "ohms" of each magnet, or what is the total resitance of all 4 magnets together.

Or, what is the maximum current drain?

Andy
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Old 06-08-2010, 11:37 AM   #4
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It is a reese brake controller. I did not install this and want to replace it asap.
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Old 06-08-2010, 11:40 AM   #5
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It's not uncommon with electric brakes, to have "glazed" lining and/or drums.

Scuff up the linings, and then scuff up the brake drums and the armature plate.

But, it also sounds like you have a wiring problem on the tow vehicle.

Or, you can have one magnet that is shorted out internally. Check the resistance in "ohms" of each magnet, or what is the total resitance of all 4 magnets together.

Or, what is the maximum current drain?

Andy
I will check the ohms when i get home on each one. as for the total I did this last night and I believe it was either 23.4 or 2.34. I can not remember.
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Old 06-08-2010, 02:36 PM   #6
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I will check the ohms when i get home on each one. as for the total I did this last night and I believe it was either 23.4 or 2.34. I can not remember.
Each magnet is about 4 to 4.5 ohms each.

Two in parallel would give you 2 to 2.25 ohms.

Four in parallel would give you 1 to about 1.25 ohms.

Four in parallel, with a full 12 volts applied, would draw about 9.6 to 10 amps. I= E/R R=EI

Additionally, you must consider the resistance (gauge) of the wiring in the tow vehicle and any resistance the connector may add to the overall total resistance of the magnet (brake) circuit.

Andy
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Old 06-08-2010, 05:14 PM   #7
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Who adjusted the controller?

First make sure the controller is mounted as per the manufactures instructions.

Common adjust method is to tow the trailer at 25 MPH and slam on the manual brake lever. Raise the adjuster till the brakes lock under this action. Once you have lockup back off on the controller just enough that the brakes no longer lock

If you are not able to reach a lockup situation then it is time to look at the brake shoe surfaces for glaze.
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Old 06-08-2010, 05:29 PM   #8
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Each magnet is about 4 to 4.5 ohms each.

Two in parallel would give you 2 to 2.25 ohms.

Four in parallel would give you 1 to about 1.25 ohms.

Four in parallel, with a full 12 volts applied, would draw about 9.6 to 10 amps. I= E/R R=EI

Additionally, you must consider the resistance (gauge) of the wiring in the tow vehicle and any resistance the connector may add to the overall total resistance of the magnet (brake) circuit.

Andy
Andy,

I just checked each brake at the wheel. I recieved 3.5 ohms from the two wires at every wheel. This was with both wires disconnected from the trailer. I would not think that every mag has an internal short but i guess anything is possible.
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Old 06-08-2010, 05:40 PM   #9
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Andy,

I just checked each brake at the wheel. I recieved 3.5 ohms from the two wires at every wheel. This was with both wires disconnected from the trailer. I would not think that every mag has an internal short but i guess anything is possible.
That is about correct for the old round magnets.

But, one of those wires could be shorted or partially shorted, within the magnet itself. All you could do,is check from one of the wires to ground.

However, it would be best to check the as you move the magnet in and out, which means taking each wheel off.

That may not be the problem, but all avenues should be checked out.

Andy
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Old 06-08-2010, 05:56 PM   #10
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Your readings are correct. Magnets are generally 3.5 ohms.

Again who adjusted the controller and to what standards?

There are several things in this equation. You have adjusted the shoes, you have checked and found no voltage drop to the magnets, you have checked the electrical integrity of the magnets. You do not know if the controller is adjusted. You can't look elsewhere till you answer that question.
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Old 06-08-2010, 06:07 PM   #11
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Shouldn't there be 9 to 12 volts at a brake magnet when the brakes are applied? This could be tested at a brake magnet wire set outside of the wheels the same place that you checked for resistance.

This time with a volt meter and some one in the vehicle either standing on the brake pedal or manually activating the controller. Engine off key on.

Or am I incorrect in this? I believe the original poster stated in post # 1 there was only 7 to 8 volts at the trailer plug with the brakes applied. I am assuming some voltage drop from TV to trailer, however I would expect to see over 8 volts if the wiring was good on the trailer plug to the brake magnets.

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Old 06-08-2010, 07:02 PM   #12
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Your readings are correct. Magnets are generally 3.5 ohms.

Again who adjusted the controller and to what standards?

There are several things in this equation. You have adjusted the shoes, you have checked and found no voltage drop to the magnets, you have checked the electrical integrity of the magnets. You do not know if the controller is adjusted. You can't look elsewhere till you answer that question.
I adjusted the controller to all positive settings. The controller was set to 10 on a scale of 1 ~ 10, 10 being the highest. This gave me the most voltage. With the stream disconnected I have 12.5 volts all day long on the same pin. As soon as I connect the stream I recieve 8 volts.

I have adjusted the shoes to where they begin to drag and then backed them off a few clicks.

Chris
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Old 06-08-2010, 07:08 PM   #13
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Shouldn't there be 9 to 12 volts at a brake magnet when the brakes are applied? This could be tested at a brake magnet wire set outside of the wheels the same place that you checked for resistance.

This time with a volt meter and some one in the vehicle either standing on the brake pedal or manually activating the controller. Engine off key on.

Or am I incorrect in this? I believe the original poster stated in post # 1 there was only 7 to 8 volts at the trailer plug with the brakes applied. I am assuming some voltage drop from TV to trailer, however I would expect to see over 8 volts if the wiring was good on the trailer plug to the brake magnets.

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Action,

I was under the same impression that under full braking with the manual slider i was to have 10 ~ 12 volts at the plug and the brake mags. I tested behind the wheel and have 8 volts there as well. Same as the main plug. I have just replaced the plug on both sides thinking that this could be the problem however it did not fix the issue. The TV has 10ga wire to the back of the plug and 12ga from the plug to the trailer. From here it drops to 14ga all the way back to the brakes each having its own pair of wires.
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Old 06-08-2010, 08:15 PM   #14
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I am not sure why you are not willing to adjust the controller as per instruction.

The controller will vary the voltage and current so just measuring voltage doesn't tell you anything.

If I recall you said you had 7.8 volts at the controller and at the brakes. This indicates the wiring is good.
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