Electric brake problem - looking for answers.

Thanks for the suggestion Rosco. The van is used often. Does the usual migration north for 5 months each winter and was last used in November 2013. In order to eliminate the van as the problem I had my Dad hook his car up to it this morning and the brakes work fine behind his tug.

Cheers
Martin

Well that leaves me out .... buggered if I know.

Yep, using my multimeter. Just working with what I have. Yep a test light would be a good addition to my tool box.

All indicator, tail and brake lights are working with the new socket so it should be ok?

Thanks
Martin

sorry but that is faulty reasoning.
Just because one thing works, that does not mean another thing is not faulty.

Step by step systematic fault finding is what will getbthe job done.

what is happening with the indicators and tail lights has not a thing to do with the brakes.

cheers

Correction...what is happening with the indicators and taile lights MAY have nothing to do with the brakes.

cheers

Yes, activating the slide control while moving and foot off the brake pedal is what I've been doing. No braking at van wheels at all.

I'm getting 12.75v at van side of plug (earth pin 3 & pin 5) with brake pedal depressed. I'm getting a progressive voltage increase up to 12.55v using the slide.

Cheers
Martin

If you are getting 12 volts at both pins, there is no effective earth on the car side of the plug, that is, there is no voltage drop across the magnet coil. If you are measuring 12 volts between the pins, the brake magnets should be energising, at least.

Thanks Brian, the earth wire just disappears into a harness at the back of the car. Where would I start looking? Does the fact that I'm getting 12.75v at pins 3 & 5 make a plug earthing problem unlikely?

Thanks
Martin

Martin, if you have a set of jumper leads, connect one of the leadss between the chassis of the van and the chassis of the car, make sure of good contact at both ends.
If an earth fault exists this should make it go away temporarily.

Thanks Brian, just tried your suggestion, still no good. :(.

Um be carefull of the asumption that the chasis of the van is earthed.

There are a multitude of earthing issues and variations....there are also many misconceptions about earthing in DC systems. systems.....sometimes I think is is wise to do away with the idea of earthing and speak in other terms.

First check that the electrical system in the van does or does not have a connection between the chasis and negative wires.

Second check that the negative wire in the socket on the car is well connected to the chasis and the chasis is well bonded to the battery negative.

There are many rubber isolations in vehicles....there should be straps bonding various parts of the vehicles to each other and the negative terminal of the battery.
Often..this is not the case or these bonds have failed.

Because the quality of the chasis bonds can vary and it is difficult to test this with instruments normal people have.
the only sure way is to inspect these earth bonds and make sure clean contact is there.

One thing with hub mounted electric brakes is that there may be an unreliable bond between the axle and the chasis.....realy there should be some sort of wire for the negative retrun from the brake magnets.

If you cant confirm or trace an earth...make a new one.

HMMM...there may be an earthing issues her..may be.

for example. IF the trailer does not have a good or any bond between the chasis and the negative wire in the plug....AND the brakes are earthed tru the chasis.

The parents tow vehicle may be providing a good earth thru the tow bar and tow ball........the original posters car may not be providing this tow ball earth.
OR, some such variation on the theme.

Just because it works ...don't mean its right.

cheers

Had a similar problem and rang manufacturer of brake controller who said very important that earth from brake controller MUST be wired to earth of CAR BATTERY NOT chassis. Definitely solved the problem.

Rheo

Thanks Ross, Sorry, I've just tested voltage again at van wheels and it reads 11.7v with brake pedal depressed.

Given that the van brakes work perfectly behind my fathers car, I would be surprised if the problem lies in the van. Not impossible of course but would be unlikely.

I will go out now and reroute the brake controllers earth wire up to the battery.

I'll be back in an hour or so :)

Cheers
Martin

It is likely the actual brake controllers earth wire is OK but the trailer plug earth wire which isn't seeing the neg of the battery.
Ideally they should all be locked to neg and as John 47 said.
If it is the brake controller earth wire at fault the controller shouldn't be able to meter out pulses to vary the signal as it has no reference earth/neg if sus.

Rerouting the brake controllers earth wire hasn't fixed the problem.Ross, if the plug earth wire wasn't seeing the neg of the battery, is it possible that I still get 11.7v at van wheels?

Martin, in your answer to me you said that you were getting 12.75v to pins 3 and 5 but that doesn't confirm that it goes right through to the brakes.
In your post above you say that you are getting 11.7 volts at the wheels.
This should be sufficient to activate the magnets, is this not happening?
Am I understanding you correctly?
Be aware that pin 10 on the 12 pin plug is also an earth. Is it possible that is the pin that has been used for the brake earth and which obviously won't be connected to your earth via your 7 pin plug unless it has been bridged in the 12 pin plug, maybe worth a check.
Still doesn't explain to me why 11.7v is not energising the magnets though.

Brian, your summary is correct and this is why I am absolutely stumped by this.

Yep 12.7v at plug and 11.7v at van wheels but magnets don't activate. However, when we connect to my Dads car the magnets activate.

Pin 10 is blank on both the van plug and the socket on my Dads car.

I have just booked it in at an auto electrician for tomorrow. I'm a bit disappointed about this as I don't like to let a challenge get the better of me. I will keep racking my brain until then.

Thanks for your suggestions.

Cheers
Martin

From what you have described the definite checking of the controllers earth not making a difference confirms what I said,
In order for the controller to meter out energy it must have that earth correct and it is still correct.

The earthing I mentioned is the same concept as Brian mentioned, the earthing of the base white wire may not be connecting to the battery negative.

Do you have both plug and base together but OPEN and can physically see the correct coloured wires on the correct pins match each others position in both the plug AND base?

Dealing with mirror reversal and frack to bunt can sometimes be an issue.

Just for the exercise, run a spare wire from the PIN 3 of base to the batt neg and see if it improves.

Hi again Ross, I have a live Anderson plug on the back of the Paj that runs directly to the battery. Using a spare Anderson connector I have made up a negative wire from the Anderson plug to pin 3. No joy.

Yes, all colours match and I've traced all wires to ensure correct placement.

I can't remember if you tried this but try earthing the car chassis to the van chassis and see if it makes a difference?

martin mate you have an earthing problem ...guaranteed.

This may not however be the only problem.

Do not assume anything is correct.....lots of faulty and incorrect things work...um ..er..just fine.

cheers

This is an earthing problem Martin.
At the risk of boring you with what you may already know, what happens when you have a faulty earth to your lights (let's say at the plug) is that the current path which would normally be through the globe filament to earth now becomes convoluted because that earth is missing, the return takes an extenuated trek through any other globes that are connected to the same earth and this generally includes back through globes in the vehicle to get to a good earth.

An example of the circuit route may be:- 12v to tail light - poor earth so current goes through stop filament - back to car via stop light wire to stop filaments (plural as there is more than one) on car - through filaments to good earth on car.
The filament with the lowest wattage (highest resistance, ie tail light,) will glow brightest, in fact just about the same brightness as if no fault existed.
This is because more voltage, in the above case almost all of the voltage, will be dropped across the tail filament.
Switch a few on together, say indicator and tail and every time the indicator globe gets 12v from the flasher it effectively shuts down the pseudo return path for the tail light (12v+ve on both sides) which will go off. It will normally be the indicators on the car and the tail light on the van that alternate.
When the opposite occurs the tail light will again glow.
This is the effect you are seeing.
Now, the brake magnets have far more wattage than the light globes which means they have less resistance, therefore the globes are dropping all the voltage and the magnets are not energising.
The reason that you were seeing that 11.7v at the brake magnets was because the globes were giving you a return path with a small additional voltage drop but the resistance was too high to allow sufficient current to energise the magnets.
Fix the earth and the problem will go away.
Because of what is happening with the lights we can be reasonably confident that all of the lighting earths and most likely also the brake earth are connected together, so you just have to find where that earth is discontinuous either on the van or the car.
Have you tried that jumper between the 2 chassis since cleaning the earth?
Possibilities are:-
1. The earth in the van plug is not connected to the van chassis.
2. The earth from the lights etc, is not connected to the van chassis.
3. The earth from the lights etc, is not connected to the earth pin in the plug on the van.
4. The two plugs are not connecting properly.
5. Any combination of the above.
You are getting a good earth indication at the car plug, so the problem is most likely in the van.
That's all I can offer at present.
Let us know what you find.

The tail lights are still flashing when hazards are also on and the 2 chassis are connected.

I'm not absolutely sure that the earth connection that I replaced is the other end of the pin 3 wire because it runs through the draw bar (chassis). Is it likely to be?

I haven't removed the van rear lights yet to do maintenance there. Are the earth wires there likely to be attached to the chassis or do they run within a harness back to another earth?

Cheers
Martin

Are you sure that jumper is making good contact at both ends?It's impossible to tell from this distance just how the van has been wired.
Van builders are a strange bunch when it comes to wiring.
I would expect there to be somewhere on the van where the wire from the front exits the drawbar and splits into the various directions for brakes, lights etc., and that's the most likely spot for joins, earth to chassis, etc. to be done.
The usual spot of choice is near the wheels.
See if you can locate that spot as it is most likely there that you will find that the wire from pin 3 is not properly terminated.
Although unusual, it is conceivable that the brake earth goes back to the lights before being connected to the main earthing conductor.
Other than the above solution, the easiest step may be to simply splice into the return wire from one of the brake magnets and connect it straight to the chassis somewhere near the wheels.
Odds are that everything will work after that as all the returns may then go back through there, provided of course that there is actually a connection from your car earth to the van chassis, Keep that chassis jumper in place for the time being to be sure.
If it all works, then remove the jumper and see what happens.
Once you get it all working you can then tidy it up.

Brian,

The problem has now been solved and I will update with the outcome but I'll address your suggestions here.

Yes it is possible that the jumper leads weren't making good contact even though I tried several points of connection on both car and van. I attached car side to various points including unpainted towbar mounting bolts on car. At the van I used various points along the draw bar including the jockey wheel holder and end of draw bar.

The point at which the van wiring splits and goes in various directions is inside the drawbar. The house battery and box which were retrospectively fitted in 2010 by and auto electrician are located on the drawbar so wiring has been altered to feed in and out of the box and drawbar. Under the van, at the end of the drawbar there is a harness that comes out and goes straight through the flloor to the inside of the van, there is that single white (earth) wire and two blue wires for the brakes.

Leigh, you are onto something and I have been wishing that I have more knowledge on how to use the ohms functions on the multimeter.

Thanks for your advice. The problem has been fixed by the auto electrician so I wont need to follow your ideas. I will now get on with posting the outcome.

Cheers
martin

No Problem, glad its sorted, while your there get them to give you a quick intro into ohm meters etc, sure they wouldn't mind.

Cheers
Leigh

Glad you got it sorted Martin.
You did mention very early on that you were getting an earth at pin 3 on the car.

Yes, still an earth of sorts at pin 3 but not sufficient for brakes to work properly even though I was getting 11.7v at van wheels.