[6pack] PDWA - Pressure Differential Warning Actuator

[John Cyganowski]

 I will toss in a few more cents to this discussion. 
Firstly, what is this thing and what does it do?  I have heard “regulator”, “brake circuit balancer” or “valve” etc.  It is none of these. It is a pressure switch. Period. It is a part of a safety system to alert the driver of an unsafe condition in the brake system. It is one the few safety system in these cars. One side of the switch is open to the front brake circuit and the other side of the switch is open to the rear brake circuit. There is a cross over that contains a metal shuttle. When the driver steps on the brakes, if the pressure in one circuit is lower than the pressure in the other circuit, the shuttle moves toward the low pressure circuit depressing the switch mounted on the cross over establishing a ground and lighting the brake fault light. 
The front and back circuits are Isolated by seals on the shuttle. There are 2 types of PDWAs. One uses double o-ring seals on each side of the shuttle to prevent a fluid leak and to allow pressure to be maintained in the circuit. The replacement o-rings are available from the usual suspects. This is the most common type of pressure switch. There is another type with seals that are like little moulded rubber cups mounted ends of the shuttle. I don’t know if these seals are still made.
Like any seal they can get old and disintegrate (they swell with contact to glycol based brake fluids) and they should be replaced. It is a very similar with wear components like the brake pads and shoes. They wear out and have to be replaced. When the seals fail, the individual circuits do not intermix. Because the brake circuits are both under pressure, the fluid looks for the path of least resistance and it leaks out the threads of the actuator switch. The leaking fluid will eat your paint quick undiscovered. 
It is neither hard nor difficult to remedy the seals in the PDWA and keep a working safety system that could possibly save your life or the life of your passenger.  But it is your car and we all have our own threshold of risk. I think it is irresponsible to recommend that someone make modifications to defeat a safety system on a mission critical system like brakes.  YMMV. 
John Cyg70 DamsonCC9252LO
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