electric over hydraulic brakes problem

Submitted: Saturday, Apr 24, 2010 at 20:33

ThreadID: 77976 Views:6949 Replies:4 FollowUps:13

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TF2

I have hydrastar hydraulic brakes on my camper trailer with a tekonsha P3 brake controller in the 4x4. Am having some intermittent issues with the system.
1 It some times come up with the message "OUTPUT SHORTED NO BRAKES)
2 Sometimes the unit applies full brake power even though I only touch the brakes gently.
All the wiring checks out OK. so it is either the controller or the hydrastar setup. I am wondering if I were to disconnect the trailer and fit a resistor between pin 3 & 5 (Earth & brake controller wire) if this would successfully fool the brake controller into believing the trailer was there. this would then test the brake controller to see if it fails without the trailer. If it doesnt fail then assuming it must be the hydrastar with the problem. Have measured from the blue wire to ground at the hydrastar unit and came up with 10 ohms. So if I fit a 10 ohm resistor this should do the job.

Update. I did fit the resistor and the controller worked as it should and did not fail at all. Any electrically minded people out their with any useful thoughts on this problem. Is it safe to assume the hydrastar unit is playing up? or does the 10 ohm resistor not really substitute the controller?

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Reply By: TF2 - Saturday, Apr 24, 2010 at 21:38

Saturday, Apr 24, 2010 at 21:38

Last line should read "Is it safe to assume the hydrastar unit is playing up? or does the 10 ohm resistor not really substitute the Hydrastar unit?"

AnswerID: 414173

Follow Up By: Notso - Sunday, Apr 25, 2010 at 09:16

Sunday, Apr 25, 2010 at 09:16

So is it all good now, or is it still playing up?

If it is still playing up, have you checked the plug and socket, sometimes there can be a stray bit of wire in the plug that contacts other pins and causes momentary shorts etc.

FollowupID: 684407

Follow Up By: Member - Jeremy W (SA) - Sunday, Apr 25, 2010 at 09:21

Sunday, Apr 25, 2010 at 09:21

This is what I would do next:

1 Jack one of the trailer wheels off the ground and make sure that the wheel spins freely.

2, Next I would apply a variable voltage (say 0.25 V to 5V) to the brake actuator.
This is easily accomplished with a variable power supply but if you do not have one a few series resistors will do.

3. Try spinning the wheel with the following:

a) R = 220 ohm (1W) for V = 0.5V on the controller
b) R = 120 ohm (5W) for V = 0.9V
c) R = 75 ohm (5W) for V = 1.4V
d) R = 51 ohm (5W) for V = 2.0V
e) R = 39 ohm (5W) for V = 2.4V
f) R = 27 ohm ( 5W) for V = 3.2V

Jeremy.

FollowupID: 684409

Follow Up By: TF2 - Sunday, Apr 25, 2010 at 11:53

Sunday, Apr 25, 2010 at 11:53

With the resistor acting as the Hydrastar unit. IE I left the trailer at home and drove around with the resistor hanging out of the plug at the rear of the car. The brake controller showed no faults. Disconnect the resistor and plug in the trailer and faults intermittently appear again.
It is not the wiring or plugs as I bypassed all of it with a wire from the controller back to the Hydrastar unit, problem still appears.

FollowupID: 684416

Follow Up By: TF2 - Sunday, Apr 25, 2010 at 11:57

Sunday, Apr 25, 2010 at 11:57

Hi Jeremy, What is it you are suggesting I am looking for when voltage applied and spinning the wheel?
I know the brakes work 90% of the time it is just the occasional full brake power being applied and the output short message that is the concern.

FollowupID: 684417

Follow Up By: Member - Jeremy W (SA) - Sunday, Apr 25, 2010 at 18:52

Sunday, Apr 25, 2010 at 18:52

Re: ... I know the brakes work 90% of the time ...

What I am suggesting is to test the actual brakes to see what's happening. By applying a voltage to the actuator (12V via the above resistors) you can see if the brakes are working in a linear (?) fashion.
Questions:

Does the actuator always return to the rest position?There may be a lubrication issue (?) .

Do the brakes work smoothly ?

So just making sure the brakes are "tip top".

FollowupID: 684449

Follow Up By: TF2 - Sunday, Apr 25, 2010 at 19:33

Sunday, Apr 25, 2010 at 19:33

I will check that out once the stores reopen and I can buy some resistors.
When the brakes do lock up though the read out on the brake controller does show that it is going to full voltage output so I'm doubting that it is just pads stuck out to far

FollowupID: 684457

Follow Up By: Member - Jeremy W (SA) - Sunday, Apr 25, 2010 at 21:41

Sunday, Apr 25, 2010 at 21:41

BEFORE YOU BUY RESISTORS:

1. Please check the actual resistance of the brake solenoid - I assumed 10 ohms from the original post.

2. Measure the resistance to see what it is and please tell me here.

3. I will recalculate the resistors if the resistance is much different from 10 ohms.

Jeremy.

FollowupID: 684473

Follow Up By: Member - Jeremy W (SA) - Sunday, Apr 25, 2010 at 21:43

Sunday, Apr 25, 2010 at 21:43

Read the original post again and it looks as if it is 10 ohms.

Jeremy.

FollowupID: 684474

Follow Up By: TF2 - Sunday, Apr 25, 2010 at 21:52

Sunday, Apr 25, 2010 at 21:52

I assume from all of this that you understand that this is electric over hydraulic we are dealing with. There is no solenoid that I am aware of.

FollowupID: 684477

Follow Up By: Member - Jeremy W (SA) - Sunday, Apr 25, 2010 at 22:34

Sunday, Apr 25, 2010 at 22:34

Sorry should not have used the word solenoid. What I meant was the magnet resistance. There are two parts:

1. The Hydrastar unit itself - which would be most reliable - brake hydraulic pressure to voltage going to the P3.

2. The power from the P3 to the trailer electric brakes - this is what I imagine needs checking.

How about that?

Jeremy.

FollowupID: 684495

Reply By: Stu-e - Sunday, Apr 25, 2010 at 22:01

Sunday, Apr 25, 2010 at 22:01

hi TF2
havnt fitted any p3 controlers so not too familar with them, we usually fit voyager series, to test the controler usually fit a 12v 55w halogen globe to the output and a long lead to drive around and test this will check your tow vehicle as when you apply the brakes the llight will glow at varying rates.

as for the trailer unit again not too fimilar with them have only worked on a couple but i googled and got hydrastar.com.au (google is your friend for tech info) it looks like the system will have a backup battery so check this is charging ok and in good condition also check your breakaway switch and assoiated wiring, dont just look at it pull it out of the clamps/ties and physically look at the whole cable and feel it for points where it may have been pinched at some point or someone has put in a join as this is the most likely place for any faults to occur. pull your plugs apart and look it only takes a little pube of wire to fault a system
good luck hope some of this helps generally if you try to remember what you did or happnened when the system faults it can be a great help to a techie ie: left turn, hard stop,
Stu

AnswerID: 414272

Follow Up By: Member - Jeremy W (SA) - Sunday, Apr 25, 2010 at 22:49

Sunday, Apr 25, 2010 at 22:49

Hi Stu,

Re:
... to test the controler usually fit a 12v 55w halogen globe to the output and a long lead to drive around and test this will check your tow vehicle as when you apply the brakes the llight will glow at varying rates ...

Excellent idea !! I have a P3 and one can check this easily via the manual control lever underneath.

FollowupID: 684497

Reply By: Member - Vince M (NSW) - Monday, Apr 26, 2010 at 16:45

Monday, Apr 26, 2010 at 16:45

have seen many a problem with Cars wired for std electric brake's when you said the wiring checked out is it wired for electric/hyd brakes most auto electrians still wire them like a std car & the only difference is The Electric/hyd units, they need/must have a power/hot wire as the electric brake wire only runs the switching in the hydrastar unit & the 12v power/hot wire powers all the unit. Some will try to run without the positive power wire but will blow fuse's & do all types of strange things.
hope this helps
regards Vince

AnswerID: 414345

Follow Up By: TF2 - Monday, Apr 26, 2010 at 19:10

Monday, Apr 26, 2010 at 19:10

Yes the hydrastar has its own power supply

FollowupID: 684589

Reply By: TF2 - Wednesday, May 05, 2010 at 20:22

Wednesday, May 05, 2010 at 20:22

Well have now changed all components ie p3, wiring and hydrastar brake actuator. Still having the same issues.
Does anyone know of any reason the red wire shouldnt go directly to the cold side of the brake pedal switch on a 2002 GU patrol 3.oL???????

AnswerID: 415557