what were these wires connected to?
#1
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what were these wires connected to?
I am trouble shooting why my AC system on my 1988 S4 5spd is not working after a recent TB/WP job done by the dealer and I came across these wires that were cut by one of the many PO. The wires are coming from the wiring harness that goes to the Temp II sensor on the right side of the motor. The wires are color coded Red/yellow and Brown/Yellow.
In my sleuthing, I noticed a missing connector on what looks like a check valve connected to the fuel system or possible a vacuum line to the fuel diaphragm on the front of the car.
I should note the car runs and drives fine. No issues, other than the previous issue with AC system.
Can some someone help me identify the source/purpose of both of these? Are there any good reasons why these would be cut/disconnected?
Context pic
In my sleuthing, I noticed a missing connector on what looks like a check valve connected to the fuel system or possible a vacuum line to the fuel diaphragm on the front of the car.
I should note the car runs and drives fine. No issues, other than the previous issue with AC system.
Can some someone help me identify the source/purpose of both of these? Are there any good reasons why these would be cut/disconnected?
Context pic
Last edited by Michael Benno; 07-14-2016 at 02:32 AM.
#2
Archive Gatekeeper
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Yes, that cutoff pair of wires should go to the 2-pin AMP connector which is the fuel tank vent solenoid valve. I think you want that to be connected, I had a failure of that solenoid valve, which led to my gas tank collapsing. Made for some nerve-wracking reinflation fun:
https://rennlist.com/forums/928-foru...el-sender.html
Roger's got the 2-pin AMP connectors for cheap.
Theory of operation on the vent valve
https://rennlist.com/forums/928-foru...el-sender.html
Roger's got the 2-pin AMP connectors for cheap.
Theory of operation on the vent valve
#3
Instructor
My wire covering these two wires is frayed so I was able to confirm these are the same wire colors you noted. They do go to the electrical connection that you show. It looks like it is connected to a diaphragm valve for some sort of breather system. Others will be able to tell us exactly how the system works.
#4
Drifting
Michael as part of the TB job the connection to the AC electric clutch has to be disconnected, so that the wiring loom can be unthreaded and allow the covers at front of engine to come off. It's a thin single wire - brown or reddish brown I think - that connects via a spade connector to the female coming from the clutch. Have you checked that one is plugged back in? It will be somewhere in front of the right hand side cam cover. I think that's the only electrical connection to the AC that is disturbed during the TB job
#5
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Michael as part of the TB job the connection to the AC electric clutch has to be disconnected, so that the wiring loom can be unthreaded and allow the covers at front of engine to come off. It's a thin single wire - brown or reddish brown I think - that connects via a spade connector to the female coming from the clutch. Have you checked that one is plugged back in? It will be somewhere in front of the right hand side cam cover. I think that's the only electrical connection to the AC that is disturbed during the TB job
#6
Rennlist Member
Thread Starter
Yes, that cutoff pair of wires should go to the 2-pin AMP connector which is the fuel tank vent solenoid valve. I think you want that to be connected, I had a failure of that solenoid valve, which led to my gas tank collapsing. Made for some nerve-wracking reinflation fun: https://rennlist.com/forums/928-foru...el-sender.html Roger's got the 2-pin AMP connectors for cheap. Theory of operation on the vent valve
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Sorry not trying to hijack.
#9
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What is the top side of that wire supposed to connect to? My Ac clutch quit turning on and I found that wire had broken from whatever it was plugged into. I can apply 12v and the clutch kicks on, just not exactly sure where it broke off from. I think its the solenoid on the cross bar?
Sorry not trying to hijack.
Sorry not trying to hijack.
I found this pic online, I see the spade connector, but wondering where the connection may be. I didn't see it in my recon this AM.
#10
Drifting
It can be checked without removing undertray. Identify the thick engine loom strung across front of engine, mounted to bottom of centre lifting shackle by two clips. As you look at the front of engine there should be a single wire emerging from the loom on the left side. The end of the wire has a small rectangular plastic piece covering the connector, and the power feed to the compressor would normally be plugged into that.
#11
Inventor
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Not mentioned in the factory doc is that the LH also increases the injector time a tiny bit to match the air leak from the vent.
(Why do I know this? I modified the vent code so I could control a set of exhaust cutouts with a different solenoid valve. )
(Why do I know this? I modified the vent code so I could control a set of exhaust cutouts with a different solenoid valve. )
#12
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All sorts of Easter eggs (albeit physiologic) in that 32K of space, no?
#13
I used a JDS Spanner to check my fuel tank vent solenoid valve, along with all the other sensor checks. I found that it was not working.
When I pulled it apart it was clogged with charcoal from the charcoal canister. I found this was due to the vacuum diaphragm between the charcoal canister and the fuel tank vent solenoid valve being defective.
I was able to clean out the fuel tank vent solenoid valve and get it working again, and replaced the vacuum diaphragm.
The fuel tank vent solenoid valve operates when you put 12V across the terminals (I did this when it was disconnected and on the bench). You will hear it click when you connect the power and you will notice that you will not be able to blow air through it when power is connected (or maybe it was the other way around, you can blow air through with power connected). Anyway, if you find it's not working check for a blockage.
When I pulled it apart it was clogged with charcoal from the charcoal canister. I found this was due to the vacuum diaphragm between the charcoal canister and the fuel tank vent solenoid valve being defective.
I was able to clean out the fuel tank vent solenoid valve and get it working again, and replaced the vacuum diaphragm.
The fuel tank vent solenoid valve operates when you put 12V across the terminals (I did this when it was disconnected and on the bench). You will hear it click when you connect the power and you will notice that you will not be able to blow air through it when power is connected (or maybe it was the other way around, you can blow air through with power connected). Anyway, if you find it's not working check for a blockage.
#14
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What is the top side of that wire supposed to connect to?
#15
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Thanks for the tip. I was able to find my connection and verify it was connected. Looks like my next step is to take it in and check the charge.