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Discussion Starter #1
Hey all, please let me know if there's a better place to post this.

I'm a mechanically inclined tinkerer and paying to have things fixed wouldn't make financial sense given the value of my car.

I've searched these forums and read so much, but can't quite find the information I need. ETKA diagram link on this site doesn't work for me and old threads without pictures have me hesitant to bite off more than I can chew.

-2000 Passat wagon 1.8T with 110k miles on it and have been thrown the dreaded P0411 CEL.

-SAIP can't be heard running ever. Cold or warm start. Fuse and relay are both good.

-Occasional whiff of exhaust is noted inside car, would that be combi valve related?

-Plan to check the SAIP hoses as well as the combi valve. Where can I find diagrams/pictures?

-Assuming I'll have to replace the combi valve and SAIP. Will follow JDigga's description in this thread :


^^This write-up makes sense to me. Does anyone know of an alternative with pictures and/or diagrams?
 

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The SAI pumps do go bad, sometimes from the accumulation of water due to exhaust getting past the SAI valve. That won't affect how the car runs, but will leave a fault code and perhaps the CEL on.
 

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The google drive links I have set up do not work? I just checked and they seem to be working.
 

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Combi valve can be tested with a vacuum pump.


SAIP can be tested by supplying it with 12V directly, by-passing the fuse and relay.

If the combi valve is bad, condensate from the exhaust can pool in the pump since it's the lowest point of the system. This will ruin the pump.

The relay can appear OK but the contacts can get burnt causing a higher resistance that can drop the voltage to the pump. I'd open it up and check the contacts or just replace it if you want.
 

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On a side-note, I wondered why the SAI pumps don't have a small hole at the bottom of it's housing to blow out any collected water. It wouldn't loose much air, but keep that blower motor dry. Kind of like steam engines which had condensate drain valves in the cylinder to purge out water.
 

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Discussion Starter #6
The google drive links I have set up do not work? I just checked and they seem to be working.
Wow! Just found those. Can't believe I missed those on my search! They're working now, what a great resource, than you VAGguy.

Thanks for the advice, everyone. I'll check the hoses and probably replace the relay first just in case it's the resistance issue causing all the troubles. After that I guess I'll try finding a cheap vacuum pump and making sure the valve is functioning properly. Last resort is messing with the SAIP itself since that seems like a slight PItA.
 

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On a side-note, I wondered why the SAI pumps don't have a small hole at the bottom of it's housing to blow out any collected water. It wouldn't loose much air, but keep that blower motor dry. Kind of like steam engines which had condensate drain valves in the cylinder to purge out water.
1st reason would be spiders. VW made those pinched sunroof drains to keep out spiders.
2nd would be that people often drive through standing water.
 

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Discussion Starter #8
Ok folks, update time:

I threw one of these 40a relays on in place of my old one:

I was concerned because it has one more prong than the one I pulled out of my car, but it fit in the ECU and nothing has caught on fire yet.

I haven't been driving the car much lately, and it usually only sees a 12 minute commute twice a day.
---Today was the first day i noticed the SAIP was running! That's a Win.
---The CEL is still on. That's a Loss.
---Also noticed the SAIP was running way longer than 90 seconds. Ran for probably 10 minutes of driving and then after sitting for a short while, it wasn't on during a second 10 minute drive. That's a ?.

My plan of action:
-Give it another week or 2 to see if that satisfies the computer and makes the CEL go away. I have a few longer drives planned, so maybe that'll help?
-Get the code checked somewhere to see if it's still P0411, maybe try having it cleared and see if it stays away?

In the meantime, I'll be observing the SAIP action and looking all over these forums for other ideas on running SAIP weirdness.

I appreciate everyone's advice. Very pleased hearing the pump is capable of pumping, as that will save me a few $ and the pain of having to switch it out completely.
 

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The SAIP should not run more that 60 (V6) or 100 (1.8T) seconds after a cold start.
It should turn off, then run for just a few seconds a little later when the engine is warm and at idle. This second, brief, run is the test cycle. My 1.8T always ran the test cycle at a particular stop sign about a mile from home; my V6 took longer to warm up. If the test cycle passes (by seeing a spike in the O2 sensor reading), the P0411 code will clear.
I can't see much detail about the relay, but it doesn't seem like it's doing it's job.
 

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Discussion Starter #10
The SAIP should not run more that 60 (V6) or 100 (1.8T) seconds after a cold start.
It should turn off, then run for just a few seconds a little later when the engine is warm and at idle. This second, brief, run is the test cycle. My 1.8T always ran the test cycle at a particular stop sign about a mile from home; my V6 took longer to warm up. If the test cycle passes (by seeing a spike in the O2 sensor reading), the P0411 code will clear.
I can't see much detail about the relay, but it doesn't seem like it's doing it's job.
Ah, ok. So, might still be relay related? I see. At least this one has the SAIP turning over. I'll look into this. Thanks!
 

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I just remembered... the VW relays have a resistor connected across the coil to help collapse the magnetic field when the relay turns off. Some other relays use diodes, which don't get along so well with the Bosch ECM, or nothing at all.

The lack of this resistor, or substitution of a diode, could explain why your SAIP keeps running long after it should.

The resistor, 680 ohms I believe, is represented by the open rectangle below the coil (slashed rectangle). The picture is the SAIP relay from my 2001.5 Fresco Green Passat, almost the only part of it I have left.

99899
 

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OP, what is the number on the top of the relay? I can check the ones I have and ship it to you so you have the right one in there...
 

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Check for signs of corrosion or charring/burning in the relay socket.
That would be the most likely thing to cause the pump to run too long.
 

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Discussion Starter #14
OP, what is the number on the top of the relay? I can check the ones I have and ship it to you so you have the right one in there...
The relay that I pulled off of my car has a great big "373" and a smaller "28/99" below that. The el-cheapo autozone relay I replaced it with has nothing written on it.
 

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Discussion Starter #15
I just remembered... the VW relays have a resistor connected across the coil to help collapse the magnetic field when the relay turns off. Some other relays use diodes, which don't get along so well with the Bosch ECM, or nothing at all.

The lack of this resistor, or substitution of a diode, could explain why your SAIP keeps running long after it should.

The resistor, 680 ohms I believe, is represented by the open rectangle below the coil (slashed rectangle). The picture is the SAIP relay from my 2001.5 Fresco Green Passat, almost the only part of it I have left.
Yeah, I'm seeing the same thing on the side of my old relay. Wish I understood anything about electronics/witchcraft, but I'm thinking we're closing in on the issue if the resistor/diode thing might be in play. I appreciate the advice.

Go figure, the $3 part-by-mail didn't work.
 

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Discussion Starter #16
Check for signs of corrosion or charring/burning in the relay socket.
That would be the most likely thing to cause the pump to run too long.
Please please please don't tell me that corrosion in the relay socket means replacing the ECU. I'm afraid to checknow.
 

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The SAIP is a fairly high current motor. Since it's a motor, it is a high inductance load which means that when the relay is opened, the current can arc across the small air gap between the relay contacts. That is the reason the VW relays use the resistor across the contacts - it gives the current another path to travel so it doesn't create an arc. The arcing will eventually erode the metal of the contacts and cause the relay to fail or it can weld them shut, which also causes the relay to fail. I assume that is why TomVW asked you to look for charring/burnt contacts.

I probably have a few of those relays lying around too so if VAGguy doesn't have one, let me know.
 

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The SAIP is a fairly high current motor. Since it's a motor, it is a high inductance load which means that when the relay is opened, the current can arc across the small air gap between the relay contacts. That is the reason the VW relays use the resistor across the contacts - it gives the current another path to travel so it doesn't create an arc. The arcing will eventually erode the metal of the contacts and cause the relay to fail or it can weld them shut, which also causes the relay to fail. I assume that is why TomVW asked you to look for charring/burnt contacts.

I probably have a few of those relays lying around too so if VAGguy doesn't have one, let me know.
No that is not the reason.
Corrosion or charring in the socket can provide a current path that keeps the relay activated for a while after it is switched off.
Contacts welded from arcing, usually stay welded and don't switch off at all.

The diode or resistor in relays is across the coil to protect the switching circuit (ECU), from high voltage when the magnetic field collapses.
 

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Discussion Starter #20
Iowegian, I appreciate the offer!

Tomvw, would the socket need to be replaced if it's nasty? Or can these be cleaned? I'll be checking it once the car gets home tonight.

I probably only need bout 10,000 more miles out of this car before I sell it. Thankfully, the only issues have been fairly minor but I'm not looking to mickey mouse any repairs and punt it on to the next broke guy. I want to sell it in good conscience.
 
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