# Electric Vacuum Brake Help



## omonoid (Aug 30, 2009)

Ok so i bought

ELECTRIC VACUUM PUMP FOR BRAKE SERVO AUDI VW 8E0927317A

and 

Omega Miniature Pressure and Vacuum Switch PSW-523

After reading this http://www.diyelectriccar.com/forums/showthread.php/brake-vacuum-pump-vw-audi-experiencei-45605.html

I have no clue how to set it up and no nothing about vacuum pumps and such.

Any links of help in setting it up would be great.

Possibly a parts list or something??

Thanks
Jake
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## brainzel (Jun 15, 2009)

This question shows me, that my last Explanation hasn't been understood 
I have tried to make a circuit diagram to shoe my wiring. I hope this can help a little.


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## omonoid (Aug 30, 2009)

thanks for trying to clear it up. What i don't understand is how to set the pressure switch, and what it does.

So you use a relay so that when the brake is pressed the pressure switch releases the vacuum and the vacuum pump creates a new vacuum?

Im trying to understand the basics first.


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## PTCruisin (Nov 19, 2009)

omonoid said:


> thanks for trying to clear it up. What i don't understand is how to set the pressure switch, and what it does.
> 
> So you use a relay so that when the brake is pressed the pressure switch releases the vacuum and the vacuum pump creates a new vacuum?
> 
> Im trying to understand the basics first.



The pressure (vacuum) switch determines when the pump needs to turn on and restore the vacuum used in braking. The switch should have 3 contacts on it so that you can wire it normally closed (NC) or normally open (NO). You will want to wire it such that is is NO when it is at the desired amount of vacuum.

When you first hook everything together, the vacuum assist brakes will be at atmospheric pressure meaning the vacuum switch will be closed, causing the vacuum pump to run and restore the vacuum to the brakes. If the switch is set correctly, it will open when the pump has achieved about 20 inches of mercury, thus shutting off the vacuum pump via the relay. 

When you press the brake pedal the stored vacuum is used to "assist" in the force applied to the brakes. As such, you will deplete the stored vacuum causing the switch to close, thus running the pump to restore the vacuum again. When the vacuum reaches the desired value, the switch will again open and shut off the pump.

Some folks install a PVC reservoir so they can pump the brakes several times before the vacuum pump kicks on.

You can calibrate the switch by plumbing in an automotive vacuum gauge that reads out in inches of mercury. That's what I did. You can pick up a cheap gauge at Autozone for about $25. I just kept mine installed and can check the amount of vacuum every time I open the hood.

You will also need a check-valve installed between the pump and the brake reservoir so that you don't lose the vacuum when the pump is idle.

I hope this helps.


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## brainzel (Jun 15, 2009)

personal supplement:
I don't use a reservoir. After one time stepping on the break, the pump goes on. The underpressure would be enough to brake twice befor start the pump, but I drive very comfortable with this solution.
I never hade any issue within the last 3000km drive.

My pressure switch is adjustable, so I tried it as long, as I thought it was perfect. It took me about five minutes, because it was so easy


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## nosmanta (Jul 24, 2011)

PTCruisin said:


> The pressure (vacuum) switch determines when the pump needs to turn on and restore the vacuum used in braking. The switch should have 3 contacts on it so that you can wire it normally closed (NC) or normally open (NO). You will want to wire it such that is is NO when it is at the desired amount of vacuum.
> 
> .



Hello!

Can you tell me where to connect the red wire(NC), white wire (NO) and black wire? Many thanks!!!


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