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1985-1998 [Subscribe to Daily Digest] |
Hello members of saabnet, and tom,
The OHMS test is only good for showing you that the electrical connections are working within the BPC... however it does not reveal wether the BPC is mechanically working or not.
As most of us know, the BPC works by electrically charging up one of TWO sides within the unit. When a charge is applied to either side, a metal disc moves in the BPC unit, to either SEAL or UNSEAL the W hose.
Charging one side SEALS the W hose off from any air pressure, and thus CLOSES the wastegate.
Charging the other side, allows pressure from the compressor housing to cycle BACK into the W hose, opening the wastegate!
The wastegate is PUSHED open by air pressure! This "pushing" happens when boost pressure from the turbo is bled through the BPC into the W hose: it pushes on the wastegate, opening the wastegate flap on the turbo, thus keeping the turbo from spinning at full force because the exhaust gas is routed around the turbine!
By adjusting the wastegate rod, you adjust HOW MUCH air pressure it takes to blow the wastegate open, which is raising your base boost level...
ANYWAYS... i'm writing all of this so when someone in the future searches for BPC TEST, they will get a complete description of the BPC system, and also the test procedure that i like to do.
So... as i stated above, if air is able to bleed from the C hose connection to the W hose connection, NO MATTER WHAT SIDE IS CHARGED, then your BPC is bad.
With rigorous cleaning, using electrical and plastic safe cleaning agents, like non-chloriated brake spray cleaner, you COULD be able to free up enough junk material in the BPC to make it seal again, but this will not always work.
SO... here's the test.
Remove the BPC from your car. But before you disconnect all of the hoses, make sure you mark which hose was connected to which terminal! If you don't you might connect the hoses back the wrong way!
I do this by wrapping a small peice of electrical tape around the top hose, the C hose, towards the very tip of the hose.
Then on the next hose down the W hose, i put the tape further back away from the tip...
...and on the last bottom hose, i put tape way back from the tip.
This is an easy, 5 second way of telling myself which hose goes to which port on the BPC unit.
For those of you who have never removed the unit, there are metal clamps that hold the hoses onto the BPC ports... these can be hard to open with your fingers. A pair of pliers should get them off... don't lose them though! without them the hoses could pop off while you are driving!
Anyways... once the hoses are off... get out your torx heads and remove the two screws at the base of the BPC unit.
Lastly, push the metal tab down on the wire connector to the BPC unit, and gently pull the BPC away from the harness...
You should have the BPC in question in your hands now!
There are a few things you should buy before attempting the test, to make your life easier... however this is all optional, depending on how smoothly you want this job to go.
Basically, what i'm suggesting is some extra vacuum hose, 2 lengths of about 6" each...
and some small gauge electrical wire with small push on tab connectors crimped on the ends.
You want three lengths of wire, about 18-12 gauge, whatever you've got handy, and you want the connectors crimped on the ends that you intend on hooking up to the BPC pins... you do not need connectors on both ends of the wires, as one end of each wire will be conncted to the battery.
Take a look at the metal tabs inside the BPC electrical connection point... you'll see that they are very small, but it's a standard size for speaker connectors. Radio shack should have the crimp on connector that will push securely onto these metal tabs...
For those of you who are in a hurry, and do not have any crimp connectors or vacuum line, all you really need is some small gauge electrical wire.
The test is as follows...
Hook a wire up to the positive battery terminal of your car battery, and hook the other end of it up to the MIDDLE tab in the BPC electrical connector.
For those of you who didn't buy the crimp connectors, you'll wish you had, because it's a pain in the BUTT to get the wire to stay without it.
Then hook another wire up to the negative battery terminal of your car... and with the other end of the negative wire in your hand... and the BPC in your other hand still connected to the positive bat terminal...
...touch the negative bat wire to ONE of the outer pins in the BPC electrical connector... it doesn't matter wich one you start with. Only touch the negative wire to the terminal for a second though, then remove it!
You might see a spark, or hear a click, this is normal, don't worry you didn't hurt anything!
NOW, blow and suck on the middle connection, the W connection... you may or may not be able to get any air through the connection...
for those of you who didn't have or buy any vacuum line, you'll be putting your mouth right on the BPC itself... this is fine, but personally i'd rather have the extra line! ;)
SO... wehter you could suck or blow air through the W hose in that first test... it doesn't matter yet... the BIG ANSWER comes when you connect the negative wire to the OTHER OPPOSITE outer connection, the one you haven't touched the negative wire to yet!
So... do just that! Positively charge the middle pin, and touch the negative wire to the other pin... you will DEFINATELY see a small spark now, and you might still hear a click! Remove the wires as you will not need them anymore...
AGain, try to blow into or suck from the W hose connection...
If air is bleeding through the W hose connection REGARDLESS of the way the coil was charged... then your BPC is BAD!!!!
If one of the sides you charged causes a seal, then the BPC is still good! And it's NOT your problem in your turbo system!
If you are one of the people without a seal regardless of charge, then here is what i like to do for cleaning.
Get some "brakleen", non chlorinated spray cleaner... or whatever you use, make sure its not harmful to electronics or plastics...
Attach the red tube on the spray nossle... and stick it into each of the BPC vacuum conections and let her rip! You may notice dirt, and other brownish stuff comming out of the BPC, this stuff obviously isn't supposed to be in there, and it's probably the main reason why the disc cannot properly make a seal anymore.
Give it a good spraying, then stop and shake the BPC up some. Dry it off from any excess cleaner... and hook it up to your battery again.
Try moving the disc back and forth on the inside by charging the opposite sides of the pins... spray some brake cleaner in the unit before you do this too...
For those of you thinking "fire hazard"... you may be right, but i did this and i'm still alive... ;) so... i'll just say, try this at your own risk kiddies! SAFETY FIRST! have a fire extinguisher on hand as you should at all times. Wear rubber gloves on your hands to prevent prolonged contact with the brake cleaner solvent, which can burn you because it's so cold coming out of the can!
Anyways, repeat these cleaning steps until you use one whole can of brake cleaner... just to be SURE the friggin thing is clean! ;) j/k
Let it dry for as long as you can possibly stand before you try the electrical test again, just to make sure that there isn't any LIQUID BRAKE CLEANER in the unit when you SUCK ON THE LINES!!!!!!!!!
Or just avoid that nightmare altogether by only BLOWING into the W hose at this point....
But you get my point, don't hurt yourself as a result of "my" test... please ;)
When you feel you've cleaned it as much as you can clean it, charge the middle pin, and ground the outer pins, while blowing on the W hose connection...
IF YOU STILL CAN'T GET THE W HOSE TO SEAL, THE BPC IS BAD AND UN-CLEANABLE!!!!!
For whatever reason, it's just done, it's had a good life, now do yourself a FAVOR, and buy a new one from Eeuroparts.com.
They cost $200, but i gurantee it will work, and it's warrantied.
If you spend $50-$100 on a used one, it might have the SAME problem as yours, with NO REFUNDS!!! this is what happened to me... i spend $250 instead of just $200...you might be luckier than i and get a working used BPC, but i gurantee my new one will outlast your used one! ;)
THERE YOU HAVE IT FOLKS!!! Whenever anyone asks you how to clean a BPC in the future... please refer them to my post, unless someone out there has a better and easier method than i do, and feels like WRITING ABOUT IT! ;)
-gavin
posted by 69.169.238...
, Mon, 6 Sep 2004 17:14:14
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