Brakes

Submitted: Monday, May 27, 2013 at 06:01
ThreadID: 128747 Views:2431 Replies:8 FollowUps:13
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Hi All
A problem with the brakes on the van that someone may be able to help me with.
One of the wheels was hotter than the other 3 wheels. So I took the van to a van place and they did the normal things like replacing some bearing and re-greasing the rest. They checked the brakes using a 12 volt battery all all worked ok.
I took the van for a test drive and the same wheel was still hotter than the others, so then jacked the van so all tyres could be spun while still connected to the vehicles electrical system.
They found that when the vehicle brakes were applied the wheel that was getting hot was locking up and the other 3 could still be spun, although 1 wheel did have some braking but still could be moved.
The magnets all made the humming sound as if they were all working.
I thought the earth on the vehicle may have been a little light so I increased the wire size but still no improvement.
Any ideas
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Reply By: Cargra - Monday, May 27, 2013 at 16:53

Monday, May 27, 2013 at 16:53
Try backing off the adjustment on the errant wheel, sounds too simple but have no idea what else could be causing the problem.

cheers graham
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Reply By: Turist - Monday, May 27, 2013 at 18:07

Monday, May 27, 2013 at 18:07
Voltage drop to the 3 wheels that are not working is a strong possibility.
Is the wheel that has some braking effort on the same axle as the one that is working?

The brake cabling should be such that if power is lost to one wheel, broken wire for example then the opposite wheel should not work to avoid unequal braking let to right.

Using a multimeter with very sharp pointed probe check voltage at magnet cable on each wheel while brake control held full on.
Voltage should be almost equal at all 4 brakes.

I had a similar problem and found that one brake wire was not soldered from the factory, just twisted together and taped up.
Corrosion eventually created a bad connection and voltage drop.

Bob
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Follow Up By: Noosa Fox - Tuesday, May 28, 2013 at 05:48

Tuesday, May 28, 2013 at 05:48
If you know an electrician with one of those metres that can measure current when placed around a cable that might show how many amps are going to each magnet.
(It is just a thought, I am not an elect)

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Follow Up By: Cargra - Tuesday, May 28, 2013 at 16:40

Tuesday, May 28, 2013 at 16:40
Interesting point about the brake cabling Bob. Are you saying that's how the cabling is originally installed or does one have to have it modified? Sounds too complex for BTI.


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Follow Up By: Turist - Tuesday, May 28, 2013 at 17:36

Tuesday, May 28, 2013 at 17:36
BTI should have wired the brakes this way.
It was done that way on both my vans.

Bob
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Follow Up By: Noosa Fox - Wednesday, May 29, 2013 at 03:43

Wednesday, May 29, 2013 at 03:43
This is how my van is wired

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Follow Up By: Turist - Wednesday, May 29, 2013 at 21:37

Wednesday, May 29, 2013 at 21:37
This is my experience.
I had a severe deterioration in braking effort so I put the van on stands and started a check of the system.
First check was to see if in fact all brakes were working so I activated the breakaway switch.
A walk around showed that the front two brakes were not working at all.
Inspection revealed that there was a broken wire , broken by stone impact about 70mm outside the front RH brake backing plate.
I repaired that and re-checked operation with the breakaway switch activated and found that I now had all four brakes working.
This posed a question, how had I fixed the LH front brake?
So I started checking by disconnecting individual wires and metering the circuit.
What I found was that the van was wired with two series circuits as shown in the diagram.
My assumption was that this is deliberate to avoid unequal left/right brake application in the event of one wheel failing.
A break at any point in the series circuit will stop that circuit working.

Now the electrician at BTI that did my job left the company about 6 months after the van was built so maybe not all vans are done that way, who knows?

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Follow Up By: Noosa Fox - Friday, May 31, 2013 at 05:21

Friday, May 31, 2013 at 05:21
Thanks Bob for the explanation.

Because there was a red and a black wire going to each wheel I thought that the Red would have been active at both wheels but obviously from your description it may not be.
Now I will have to check under my van and see exactly how the wires run, but it may well be wired as your van is as that would explain why I had a drastic loss of braking when the wire on one wheel broke. Instead of loosing just 1 wheel I might have lost 2 wheels.

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Follow Up By: Turist - Friday, May 31, 2013 at 05:45

Friday, May 31, 2013 at 05:45
Might depend on which electrician did the job Brian.
There have been a few doing the job over the years.

Bob
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Reply By: Spannl - Tuesday, May 28, 2013 at 06:17

Tuesday, May 28, 2013 at 06:17
Thanks everyone for your advice.
I took the van back to the van repairer today and they worked on it again.
I was there when they bought it back from a test drive and the front passenger side brake was smoking hot the front drivers side was hot but not as hot as opposite side front, back 2 were warm.
The repair said that the front brakes should be hotter than the back as they work harder than the back just like a car!
I questioned this as the van does not have a load sensor valve like a car.
Happy to hear what your thoughts are on front to back axle braking if they should be equal in braking force there for temp.
On the question of wheels that are getting hot.
Front passenger side main wheel getting hot.
Front driver side lesser in temp
Back 2 hardly hot to cold.
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Reply By: Noosa Fox - Tuesday, May 28, 2013 at 18:24

Tuesday, May 28, 2013 at 18:24
I think I would have a more knowledgeable person fix the brakes.
On our trip to Melbourne I noticed that the van brakes were not operating as good as they should and I increased the power at the controller and the boost
While in Victoria I checked and adjusted the brakes and bearings and found that one wheel had a broken wire.
After the repair and adjustment I have driven over 500km and made some hard braking and each time I stopped checked the wheels for temperature in case I had over adjusted something but all wheels have been cold to touch, and braking has been good and I can feel the van holding the vehicle back.

I cannot see how when one wire comes from the car supplying the brake current and then that goes to 4 wheel brakes if 1 wire breaks at a wheel how that would affect the current going to the remaining 3 wheels would be affected or how the wheel opposite the broken wire wheel could be different to the other 2 wheels.

I know that when I tried a multi meter to check voltage at the brake I couldn't get a reading and now I have a light to check to see if there is power across the wires.

Brian
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Follow Up By: Turist - Wednesday, May 29, 2013 at 02:57

Wednesday, May 29, 2013 at 02:57
Brian if each axle group is wired separately in series and any one wire on that circuit breaks then both left and right brakes on that axle will not work.

If all four brakes are wired in parallel then if one wire breaks then only the brake connected to that wire will stop working.
The issue here is that the uneven left right braking can create instability as well as loss of braking effort.

One axle losing braking effort on both sides causes lack of brake effort but you still have equal braking.
Some manufacturers connect in individual series circuits, some in parallel.
My BT has individual series circuits, one on the front axle, one on the rear.

Some will argue that there is a possibility that the second magnet in a series circuit will suffer some power loss through voltage drop but this does not seem to be the case.

Still only one wire from the car Brian, where it goes next is the tricky bit.

Bob
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Follow Up By: Noosa Fox - Wednesday, May 29, 2013 at 03:22

Wednesday, May 29, 2013 at 03:22
I see what you mean now Bob, BUT

If the brake supply wires come down the left side of the van and then divide and go to front and rear axles so that line "A" does the front 2 wheels and line "B" does the rear.
I have a couple of questions for you.

Then the wiring in series would go to the left wheel and onto the right wheel.
If a rock takes out the wire going into the right wheel brakes how does that affect the left side?

Similarly the supply wire to the left side wheel would have to go to the magnet where another would then come back out through the backing plate and on to the brake on the right hand side.
My van has the wires going to each axle as you describe but the wires going into the first wheel join at the junction where the supply goes to the other side of the van so they are in affect now in parallel. Each time we have had a broken wire to any of the brakes it has been just before it goes into the backing plate of where it has that severe kink as it goes through the backing plate.

How can a broken wire where it goes into the backing plate of one wheel affect the braking on the other wheel as I don't believe that any of the vans would have the supply wire joined inside the hub at the magnet?

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Follow Up By: Turist - Wednesday, May 29, 2013 at 03:31

Wednesday, May 29, 2013 at 03:31
Give me some time & I'll try to draw a curcuit diagram for you.
Bob
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Reply By: Noosa Fox - Wednesday, May 29, 2013 at 00:32

Wednesday, May 29, 2013 at 00:32
Just a thought I had while driving.

If they have fitted new brakes and backing plates then some may be fitted on the wrong side and if so would not be doing much braking while the one facing the correct way would be doing all the work.

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Reply By: The Hob - Wednesday, May 29, 2013 at 04:24

Wednesday, May 29, 2013 at 04:24
I believe that circuit design may not be the problem. Can't be series circuit unless power goes through one side and into the other side before earthing out. I doubt this is so.

Problem is more likely to be inside the brake drum. Generally there is a leading and a trailing shoe and if these are assembled back to front or left side is on the right then problems can arise.

As noted by above posts, this can lead to varying brake applications.

Alan

My brakes seem to be effective without side to side temp variations
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Reply By: MuzzaJ - Wednesday, May 29, 2013 at 18:59

Wednesday, May 29, 2013 at 18:59
Hi All
This post is from a regular Poor Dumb Bastard Award receipent .... (three in total, so far), so take it easy on me.
I have been following the post/replies regarding Spanni and his BRAKES issue. I am interested in any answers to the following question.
If Spanni was to disconnect his trailer plug ie no power to the BT and then take the BT for a drive (slowly and carefully of course) then pull up using only the tow vehicles brakes. If the heating problem is still be evident. The question is ...What has it to do with a voltage problem within the braking system?
As a regular PDBA receipent and having few qualifications to make comments on such matters, I maintain that the HOB is on the money ie it is not voltage but a brake drum issue.
I am interested in any further comments
Murray

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Follow Up By: MuzzaJ - Wednesday, May 29, 2013 at 21:03

Wednesday, May 29, 2013 at 21:03
Hi All
Spelling correction "RECIPIENT" No wonder I've been awarded 3x PDBAs
Good health and safe travelling
Murray

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Reply By: Spannl - Wednesday, Jun 05, 2013 at 05:46

Wednesday, Jun 05, 2013 at 05:46
Thanks All for your replies
Just to answer some of your responses
I have not adjusted the brakes as I believe the caravan repairer should have carried out this when they had all the wheels off.
I have not taken the van for a drive without the power connected but as the back wheels are not working there must be something going on with the system.
I spoke to BT late last week and got some info from them on how they wire the brakes up.
And also found out that they have have a case like this before.
I also spoke to Simplitiy which backed up some of BTs tests to be carried out.
Both said to test the amps to each wheel with brakes applied using a clamp on amp meter.
They say it should be around 2amps at each wheel.
BT said in the case they had in the past they could not find anything wrong with the system so they replaced the brake backing plate on the one getting hot and it fixed the problem but they could not explain why.
I have ordered a clamp on amp meter that reads DC amps at low amps and a brake adjusting tool to carry out these tests and adjustments.
The other thing BT said is if the backing plate is an ALCO to throw it away and only use Dexter backing plates.
My question to all is does anyone have experience with these backing plates and what have you found works.
Simplitiy say they fit both backing plates and have not heard of any problems with either.
Also does anyone have knowledge of where to purchase Dexter backing plates in NSW?

Thanks All

Laurie
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Follow Up By: Noosa Fox - Wednesday, Jun 05, 2013 at 05:55

Wednesday, Jun 05, 2013 at 05:55
You can purchase Backing plates direct from Simplicity. That is where I get mine from when required.

I know it will not show you the AMPS but you can easily check the power supply using a light rather than a meter. The LED side lights are ideal to make sure you have power there.

Brian
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Follow Up By: Turist - Wednesday, Jun 05, 2013 at 07:52

Wednesday, Jun 05, 2013 at 07:52
I have done over 100,000 Kl with Alco brakes, absolutely no problems with the backing plates, overheating or other mechanical issues.
BT are guessing I suspect.

Have you done the voltage check that I suggested?
It may save you the cost of another meter.

Bob
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