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Discussion Starter · #1 ·
Hi guys. I have a 2005 Passat 1.8T AWM that is getting some electrical issues. The most recent issue is the the a/c condenser fan is not turning on. So I've by passed relay 373 that is for the low speed the fan turn on right away, so I did the same thing to the relay 370 which is the one for high speed and the fan is turning on. Fuse 40amp is good, compressor is turning on. Please help.
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Do the relays get power when you turn on the a/c? If not, Does the a/c button on the dash light up when it's pressed? Did you scan the car with VCDS to check for any codes?
 

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Does the fan run if 12 volts is applied directly to the fan? Easily done with the large harness connector and a couple of wires.
2 years ago the fan in my wife's Passat wasn't working and I thought I would be in for some dreaded electrical gremlin chasing.
Turns out the fan itself was toast. Bought a new fan last year, all is good. I got lucky on that one.

I got to admit I'm impressed though, 20 years that fan lasted. All of that time except the last 5 years up in the rust belt and then down here in the furnace of the U.S. Not bad, not bad at all.
 

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Discussion Starter · #5 ·
Does the fan run if 12 volts is applied directly to the fan? Easily done with the large harness connector and a couple of wires.
2 years ago the fan in my wife's Passat wasn't working and I thought I would be in for some dreaded electrical gremlin chasing.
Turns out the fan itself was toast. Bought a new fan last year, all is good. I got lucky on that one.
Fan works fine when apply 12v from the battery.
 

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Do you have a copy of the Bentley Manual? Do the relays not have power on just the trigger wire or the power supply itself? You will need to trace the issue back from there, but someone with a Bentley or better memory than I will have to guide you.
 

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FrescoGreen01.5 or Tomvw would be my two picks for electrical stuff.
 

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Does the cabin air flow fan work correctly at all speeds ?

With the A/C switched OFF, which of the 3 fan control relays have about 12V on terminal 85 ?
With the A/C switched ON, which of the 3 fan control relays have about 12V on terminal 85 ?

When you did the tests indicated in post #1, did the fan run at low speed for one test and high speed for the other ?
 

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Discussion Starter · #9 ·
Do you have a copy of the Bentley Manual? Do the relays not have power on just the trigger wire or the power supply itself? You will need to trace the issue back from there, but someone with a Bentley or better memory than I will have to guide you.
I don't have Bentley manual. The socket has power on terminal 30, but not to trigger the relay. I am doing it manually with a jumper cable from terminal 30 to terminal 87.
 

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Discussion Starter · #11 ·
Does the cabin air flow fan work correctly at all speeds ?

With the A/C switched OFF, which of the 3 fan control relays have about 12V on terminal 85 ?
With the A/C switched ON, which of the 3 fan control relays have about 12V on terminal 85 ?

When you did the tests indicated in post #1, did the fan run at low speed for one test and high speed for the other ?
Cabin blower works just fine on all three speeds.
Cooling fan relay 373 which is on the first panel relays has 12v only when the a/c switched on.
Radiator fan first speed relay 373 on the back panel relays has no 12v on terminal 85 on either ON or OFF
Radiator fan second speed
relay 370 on the back panel relays has no 12v on terminal 85 on a/c switch either ON or OFF.
 

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Discussion Starter · #13 ·
That would most likely be a faulty fuse #51 (30A) on the Aux relay panel, or its wiring is faulty.
Check fuse with a meter or test lamp.
The fuse is 40A and is good. Since I had to by pass the relay 370 which is the high speed, I used a jumper cable from terminal 30 to terminal 87a to supply 12v to the radiator fan.
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