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Discussion Starter · #1 · (Edited)
Why ask others when you can find out for yourself?
I suspected a bad BPC valve but didn't realy understand fully the inner workings. I got it on the bench and cut round the seam and then prized it apart. Here is how it works a metal disk sits between 2 opposing electro magnets which have holes in them. These holes port to the end connectors so when the magnet is activated the disk is pulled over the port to block the passage of air. There is also a central port at the edge of this disk which this connects to whichever port is not blocked. I pulled apart 2 BPC valves and both of the metal disks were missing substantial parts although not enough to stop proper sealing when the magnets are actuated. However their non round shape probably makes them jam in one or the other position. The default setting should alow air to pass through all the ports but mine was blocking the return port to the intake. It would unblock when 12v was applied but it never went loose as it should. A new BPC valve will be ordered.
 

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Have you worked out a diagnostic procedure that would be so helpful to so many here.?
 

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A few pictures on the subject are available here. And you're right that membranes do crack with age, causing the valve to fail. I wonder if you can pry one of the magnets out and replace a broken membrane with a new piece.

 

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Wouldn't that be something,repairing a $200 item with $2 in parts and one hour in labor..

I'd love to see a lot more of this, its good for the economics and the environment.
Too bad there are not any $2 parts....yet ?
 

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Discussion Starter · #5 ·
I reasembled it only to find that one of the coils was now showing less than 1ohm:roll: resistance so I threw it away and ordered a new one from PFS ( the cheaper non Saab version). As the disk was damaged it was probably not going to work properly anyway.The disk is precision ground hardened steel so not something you could easily make. As for diagnostics - I'm not sure anymore. The disk oscilates at a very high frequency so if it's damaged or one of the coils is a bit tempremental it could drasticaly effect it's function but may still pass the standard blow through and resistance tests. My advice is to borrow a known good one and see if it solves your problem and then buy a new one. I've had it with 2nd hand ones - 3 I bought off ebay have been faulty. They wear out as well - the metal disk erodes the brass housing and is likely to effect it's function. It's a scandal that it's so expensive:evil: - even the new 3rd party made item is not cheap. I can see why MBC's are such a popular alternative but with an upgraded ECU I'm not happy running without any boost control.
 

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Is it the same configuration as the control valve on c900's, they seem to last alot longer, i've got a couple of them kicking about aswell:D .
 

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Shirozina said:
I reasembled it only to find that one of the coils was now showing less than 1ohm:roll: resistance so I threw it away and ordered a new one from PFS ( the cheaper non Saab version). As the disk was damaged it was probably not going to work properly anyway.The disk is precision ground hardened steel so not something you could easily make. As for diagnostics - I'm not sure anymore. The disk oscilates at a very high frequency so if it's damaged or one of the coils is a bit tempremental it could drasticaly effect it's function but may still pass the standard blow through and resistance tests. My advice is to borrow a known good one and see if it solves your problem and then buy a new one. I've had it with 2nd hand ones - 3 I bought off ebay have been faulty. They wear out as well - the metal disk erodes the brass housing and is likely to effect it's function. It's a scandal that it's so expensive:evil: - even the new 3rd party made item is not cheap. I can see why MBC's are such a popular alternative but with an upgraded ECU I'm not happy running without any boost control.
Just curious what did you pay for the non Saab BPC?
 

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Discussion Starter · #8 ·
The valve is similar to the APC solenoid in that it has 3 ports but it works at a much higher switching frequency 70-90hz. The APC solenoid works by switching a current on and off to switch the flow between the actuator and the intake whereas this unit is operated by a variable AC voltage or waveform current. PFS sell's an alternative part for around £90 or teh genuine part for £140. IMO this should be a £25 part!
 

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Shirozina said:
... PFS sell's an alternative part for around £90 or teh genuine part for £140. IMO this should be a £25 part!
LOL, yeah, if only all parts were sold at reasonable costs! Have you seen what goes into a Bosch DV? Those things shouldn't retail for more than £5!
 
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