ABS Pressure Switch. SUPPLIER FOUND!

[G_Reaper]

Hi

OK I have found a supplier who claims they can manufacture the pressure switch for the ABS system.

All I need the is the switch operating on and off settings in Bar. I also need the screw thread type. The supplier manufactures for the motor industry the switches would be pre set with the required values from the factory. I also need to know if the switch contacts are normally in the open or closed position.

How many people would require one would be helpful.

If someone can help with the technical specs I can have the switches within 2 weeks. The price will NOT be hundreds of pounds either!!!

Cheers Mike

[sailorbob]

<1800 psi (124.1 bar) brake warning lamp on, normally closed

between 2200 - 2700 psi (151.7 - 186.2 bar) pump on, normally open

Edited April 18, 2011 by sailorbob

[G_Reaper]

<1800 psi (124.1 bar) brake warning lamp on, normally closed

between 2200 - 2700 psi (151.7 - 186.2 bar) pump on, normally open

When you say brake warning light on do you mean the light on the dash and not the lights at the rear of the car?

Does this mean that the pumps switching circuit power is constant and the pressure switch breaks the circuit tripping a relay to activate the pump at 151.7 Bar closing the circuit de activating the relay at 182.2 Bar?

Sorry to be so pedantic I need to make sure all the info I supply is correct and that I have understood all info correctly.

Cheers Mike

[sailorbob]

The brake warning lamp is the tell tale on the dashboard.

When the normally open contacts close they ground the accumulator pump relay coil.

[X180R17]

The switch is not a simple pressure switch. its actually several things in one and not simple in operation. The low pressure warning circuit is fairly simple. Its open below the low pressure warning point of I think 1800psi so in normal operation on the esprit its closed (above 1800 psi). When it opens below 1800 psi it breaks the ground to the ECU and that signals the ECU to operates the warning lights apropriatly. The pump motor switch is the more complicated part. It is on (closed) whenever the pressure drops below 2200 psi and off (open) above 2700 psi. There is a 500 psi dead zone where it does not switch over though. This is what allows it to turn the pump on at 2200 psi and then keep it on until the switch opens at 2700 psi. And then keep it off until the pressure drops back down to 2200 again. Without that the switch would activate whenever youtouched the brake and the pressure dropped even the slightest amount. Mechanically its like a little overcenter metal clicker in there. With pressure against one side and a spring against the other. But it has a certain mechanical resistance to popping overcenter that gives it the dead zone in the middle. Pressure drops far enough (2200 psi) the spring can push the clicker over to activate the pump and then when the pressure gets high enough (2700psi) it can push it back to shut off the pump.

If they can reproduce that then you have a winner!

Dave

[sanj]

Mike, the switch is a bit more complex than most folks think. It is actually two switches in one, and is not strictly just a pressure switch(es).

Terminal A is ground.

Terminal B is connected to terminal A internally (switch closed) when the system pressure drops below 2200 psi. This provides a ground path for the negative side of the pump motor relay, turning the ABS pump on. When the pressure reaches 2700 psi terminal B is disconnected from terminal A (switch open). As the pressure falls towards 2200 psi, the switch remains open, until the low threshold is reached again.

Terminal C is the brake low pressure warning. When system pressure is good, it is connected to terminal A (switch closed), grounding an input to the ABS ECM, which is thus made happy. If the pressure drops below the warning level, terminal C is disconnected from terminal A (switch open), causing the ABS ECM to see a voltage at the input, thus making it unhappy. It also signals the lamp driver module, which turns on the red brake warning light. The ECM controls the ABS warning light.

(Thanks to Dave C. for the info he provided me about the switch construction.)

From the ABS manual:

The pump motor circuit consists of a Pump Motor, Pump Motor Relay, Accumulator Pressure Switch and ABS Controller. When the ignition is in RUN, voltage is,applied to the Pump Motor Relay coil from ABS fuse "A". If accumulator pressure drops below approximately 2200 PS1,the Accumulator Pressure Switch closes, grounding the Pump Motor Relay coil and energizing the relay. The relay contacts close, allowing voltage to be applied to the Pump Motor and the "Pump On Input" Terminal at the ABS Controller. The Pump Motor will continue to run until accumulator pressure reaches approximately 2700 PSI, when the accumulator switch contacts open causing the Pump Motor Relay to de-energize. The ABS Controller does not control the operation of the pump motor but does monitor the Pump motor circuit for proper operation by way of the Pump On Input. If the controller detects a problem in the Pump motor circuit such as excessively long pump run times or no pump runs after several brake applications, the controller will set a code and warn the driver.

The Lamp Driver Module turns on the Brake Tell Tale when accumulator pressure falls below approximately 1800 PSI. The Lamp Driver Module is grounded at Terminal C through the accumulator switch. When accumulator pressure falls below approximately 1800 PSI the switch opens. The Lamp Driver Module senses the Accumulator Pressure Switch is no longer grounded, and turns on the Brake Tell Tale by grounding it.

Edited April 18, 2011 by sanj

[sailorbob]

I actually think the switch is quite simple, it's just that there are two switches combined into one unit; an on/off pressure switch and a differential pressure switch both sharing a common terminal. Unless a reasonably priced alternative to the obsolete part becomes available all I'll do is use two switches with a T adapter into where the original goes when the time comes for me to replace mine.

[X180R17]

Certainly nothing wrong with doing a manifold and 2 seperate switches, and the straight pressure switch for the warning is pretty simple. The difficult part is still getting the pump control part, because it needs 2 pressure points. It would almost be easier to do 3 simple pressure switches and set up a self energising relay to handle the pump cycling. Electrically its pretty simple. A low pressure switch that activates a relay below 2200 psi to run the pump. Set the relay to keep itself energised once started and then add a second pressure switch to cut power to the relay above 2700 psi, thus turning off the pump and resetting the relay.

Low pressure will activate the relay and it will keep itself going until the high pressure switch shuts if off, thus keeping the pressure between the switch points.

Dave

[sailorbob]

It can be kept simple, differential pressure switches compatible with brake fluid are readily available in the pressure range required.

[X180R17]

What do you mean by differential pressure switch? To me that means a switch that works off of the difference between 2 fluid pressures which isn't what were looking at here, so I'm confused. I'd love to know that a standard pump activation switch exists in the pressures desired.

[sailorbob]

I am probably using the wrong terminology, maybe window comparator (aka high/low) is more accurate? Someone on the forum found a UK supplier a long time ago (pre forum face lift) but I cannot find the thread any more

Using two switches is obviously far messier than the stock switch, hopefully Mike's research will come to fruition.

[G_Reaper]

Hi

Initial response seems that 2 switches would be easier although the manufacturer is checking this out.

He does not seem concerned about the pump switching or the warning lamp, but he is checking there range and previous manufacture records to see if they have made such a switch before.

Watch this space.

Cheers Mike

[Glyn Wise]

Good news re switch,as mine is playing up,if I remove it to clean it with brake cleaner do I need to drain the brake system of fluid ?

Oh happy day .......... Glyn

[ramjet]

Why reinvent the wheel? I posted this a fair while back. The price can be reduced if we get a group buy together. Steve will ship to anywhere and the system has engineering approval. Steve has sold a fair few of these to esprit folk around the world and to date has not had one comeback on him.

Pressure switch solution

[lotus4s]

Glyn,

No you don't have to drain the fluid but you should de-pressurize the accumulator by pressing the brake pedal 40 times before removing the switch.

[G_Reaper]

The problem with Steve's solution is it still way too expensive for what it is. The switches in cost terms are small percentage of the price Steve is charging.

What do you mean by engineering approval?

Cheers Mike

Edited April 22, 2011 by G_Reaper2

[ramjet]

You're not allowed to change a braking system on a car over here with it being ok'd. If you had an accident and it was discovered that you had modified the vehicle braking system, insurance would not cover you unless the modification is approved. And Steve is also professional enough that if he is going to sell a solution, he was going to make sure that it had engineering approval to be adequate for purpose.

Understand that the system he is supplying is a low & high pressure switch, the loom for it all and the manifold which is double sealed at all connections to not leak under the pressures. Both the switches that Steve has sourced are required to be sent to another company to be calibrated. Once you get it you basically screw it straight in and alter the original loom to the new loom.

Plus, I suspect Steve is also recouping all the time it took him to develop a solution.

His price still beats the price for the switch made from unobtainium.

[G_Reaper]

Thanks Ramjet,

When you say over here, where is that? Are you also in Australia?

I am sure Steve's solution works great and will most probably be cheaper than the Lotus alternative (if it ever happens).

However I still am quite certain that as this supplier supplies most major car manufacturers a cheaper solution is around the corner. T piece manifolds are I believe already available with the required threads and pressure ratings, if not I am sure they can be made at a very reasonable price using the Nissan engineering suppliers local to me.

Having already contacted the DVLA in the UK about removing my ABS system and also spoken with my insurance company about brake modifications it would appear this would not be an issue in the UK. As long as the car passes an MOT and your insurance company are aware of the mods that seems to be that.

I am trying to put together the full package the same as Steve and if it works it will not have taken very much time at all. I appreciate he must have the red tape to pay for but this would be a system that alot of other nations may be able to use without having to pay for the red tape Steve has to suffer. (That would be a first for the UK).

Regards Mike

[ramjet]

Yes I'm in Australia

[Glyn Wise]

Thanks Jim

Had the switch off and gave it several clean outs with brake cleaner and an over night soak

in WD40,with some gentle heat from a fan heater....works a treat

Cheers Glyn