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Discussion Starter · #1 ·
Hey everyone,
I've been trying to read everything on this forum about auxiliary fan problems for 2 weeks and I'm still not sure what's going on with my daughter's 01 Passat 2.8.
It started with a blown 40 amp fuse, then after "some" troubleshooting determined that the fan control module was the culprit. Replaced it and the fan worked fine for less than a day. I then assumed that the fan must be faulty because I had 12v going to the fan. Replaced that and now I'm back to square one.
Started looking harder at voltage/grounds and realized that the 5amp fuse had no power to it. Now I'm trying to figure out where to go from there. I do have a Bentley Manual and it shows a blue wire (coming from the generator?).
I loosened the fuse panel/relay panels to get a better look, but everything is so tight its hard to trace a small wire.
Has anyone else ever seen or heard of this issue before?
 

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Which 5A fuse do you think has no power ?
The Blue wire from the alternator goes to the instrument panel only.

The fan should run any time that the engine and A/C are running.
If the A/C is off, the fan runs only when the coolant is very hot.

Have you checked the coolant fan relay ?
 

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OP, the appropriate Bentley schematic is either 33 (Climatronic) or 56 (manual A/C controls). I'm guessing you're looking at 56, and they're very similar anyway.

You do need power for both fuses, S42 & S51. S42 is the power to run the fan and I think the afterrun coolant pump V51. S42 is the control power, which powers the relays in the control module. I believe these fuses are both on the 8-position relay panel per page W97-2 (although Bentley could be clearer). For your edification, the control module contains the same relays and functionality as the 1.8T (which uses discrete relays and resistor), plus the after-run coolant pump controls. The 1.8T circuit is Schematic 57/3.

So, about that blue wire: it comes from splice A17 in the instrument panel wiring harness. The tricky thing is this schematic doesn't show every wire in that splice! I guess you're somehow magically supposed to know where else to look...

Lacking magic, we can look for A17 on the instrument cluster schematic 48/6--not much to see there. And on the Generator schematic 69/2... So, the biggest wire comes from the generator D+ terminal (alternator, really).

I have to assume this terminal gets 12 volts when the alternator is working properly and the alternator light on the dash goes out. That means you'll have to test for power with the engine running--not just key on.

That was a lot of words, but I hope it helps a little. Tomvw is correct (per usual) that the electric fan only runs when the A/C is on or the engine is really hot. The full operating logic is:
Low speed if A/C on or engine temperature (at lower radiator outlet) hot.
High speed if A/C high pressure switch closes or engine temperature really hot.

The engine temperatures that activate the fan are on Bentley page D19-2, item 13. If the mechanical fan (and viscous clutch) are working properly, the electric fan will seldom run except on low for the A/C.
 

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So, about that blue wire: it comes from splice A17 in the instrument panel wiring harness. The tricky thing is this schematic doesn't show every wire in that splice! I guess you're somehow magically supposed to know where else to look...

Lacking magic, we can look for A17 on the instrument cluster schematic 48/6--not much to see there. And on the Generator schematic 69/2... So, the biggest wire comes from the generator D+ terminal (alternator, really).

I have to assume this terminal gets 12 volts when the alternator is working properly and the alternator light on the dash goes out. That means you'll have to test for power with the engine running--not just key on.
I believe you will find that blue wire from the alternator, connects to T32A/12 on the cluster, and nothing else.
It is a signal voltage, not supply.
With ignition ON and not running, it acts as a ground for the alternator/battery warning light, and has a low voltage on it.
When the alternator is running the regulator supplies a signal voltage of about 12V to the Blue wire.

Do NOT connect anything to that wire.
Note: There are some White/Blue and other similar coloured wires that have multiple connections in splices.
 

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Discussion Starter · #5 ·
Which 5A fuse do you think has no power ?
The Blue wire from the alternator goes to the instrument panel only.

The fan should run any time that the engine and A/C are running.
If the A/C is off, the fan runs only when the coolant is very hot.

Have you checked the coolant fan relay ?
Tomvw
Hey everyone,
I've been trying to read everything on this forum about auxiliary fan problems for 2 weeks and I'm still not sure what's going on with my daughter's 01 Passat 2.8.
It started with a blown 40 amp fuse, then after "some" troubleshooting determined that the fan control module was the culprit. Replaced it and the fan worked fine for less than a day. I then assumed that the fan must be faulty because I had 12v going to the fan. Replaced that and now I'm back to square one.
Started looking harder at voltage/grounds and realized that the 5amp fuse had no power to it. Now I'm trying to figure out where to go from there. I do have a Bentley Manual and it shows a blue wire (coming from the generator?).
I loosened the fuse panel/relay panels to get a better look, but everything is so tight its hard to trace a small wire.
Has anyone else ever seen or heard of this issue before?
If I'm on the right diagram (Y571) for 2001 Passat 2.8L ATQ, then s51 is the signal wire to the fan control module. I don't think this car has any external relays related to the aux fan. They're all internal to the module. Correct me if I'm wrong because I'm starting to second guess everything I've checked so far.
Also, neither the aux fan or the after-run pump will come on at all. AC on or off, car at 190'.
 

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Discussion Starter · #6 ·
Also, the ac pressure switch, coolant temp switch, fan control module, and the fan itself has been replaced.
I believe you will find that blue wire from the alternator, connects to T32A/12 on the cluster, and nothing else.
It is a signal voltage, not supply.
With ignition ON and not running, it acts as a ground for the alternator/battery warning light, and has a low voltage on it.
When the alternator is running the regulator supplies a signal voltage of about 12V to the Blue wire.

Do NOT connect anything to that wire.
Note: There are some White/Blue and other similar coloured wires that have multiple connections in splices.
I do see that on Y333 (no. 33/7). But I'm still baffled as to why the fan won't come on. It's 100'F today with AC on, but no fan or after run pump.
 

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Discussion Starter · #7 ·
OP, the appropriate Bentley schematic is either 33 (Climatronic) or 56 (manual A/C controls). I'm guessing you're looking at 56, and they're very similar anyway.

You do need power for both fuses, S42 & S51. S42 is the power to run the fan and I think the afterrun coolant pump V51. S42 is the control power, which powers the relays in the control module. I believe these fuses are both on the 8-position relay panel per page W97-2 (although Bentley could be clearer). For your edification, the control module contains the same relays and functionality as the 1.8T (which uses discrete relays and resistor), plus the after-run coolant pump controls. The 1.8T circuit is Schematic 57/3.

So, about that blue wire: it comes from splice A17 in the instrument panel wiring harness. The tricky thing is this schematic doesn't show every wire in that splice! I guess you're somehow magically supposed to know where else to look...

Lacking magic, we can look for A17 on the instrument cluster schematic 48/6--not much to see there. And on the Generator schematic 69/2... So, the biggest wire comes from the generator D+ terminal (alternator, really).

I have to assume this terminal gets 12 volts when the alternator is working properly and the alternator light on the dash goes out. That means you'll have to test for power with the engine running--not just key on.

That was a lot of words, but I hope it helps a little. Tomvw is correct (per usual) that the electric fan only runs when the A/C is on or the engine is really hot. The full operating logic is:
Low speed if A/C on or engine temperature (at lower radiator outlet) hot.
High speed if A/C high pressure switch closes or engine temperature really hot.

The engine temperatures that activate the fan are on Bentley page D19-2, item 13. If the mechanical fan (and viscous clutch) are working properly, the electric fan will seldom run except on low for the A/C.
I would definitely check for power at A17 if I knew where it was physically located.
So, if no power there its an alternator/voltage regulator issue?
 

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OP, the correct schematic depends on whether you have Climatronic or not. If Climatronic, 58/7 is correct, and the fan control module wiring is virtually identical anyway.

This is puzzling, since you've replaced nearly everything. I presume you've verified with a meter the 40A and 5A fuses (on the 8-position relay panel) are still good?

If so, the next thing I'd check is the ground to the module. It's inside the car (circled 30, beside fuse panel), but worth looking at. A faulty ground would certainly keep all this from working. Be sure to measure resistance, rather than using the continuity mode. You should have way less than 1 ohm--virtually zero compared to your meter lead resistance (i.e. probes shorted together). The fan, in particular, pulls a lot of current.

If you can, check for voltage and ground at the control module connector. I don't know exactly how difficult it is to get at (never had to).

Since the 5A fuse is powered from the alternator (sorry Tom, just reading the schematic!), I tend to think the after-run coolant pump is powered from the 40A fuse, as well.
 

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An above-the-car method of testing the ground just occurred to me:
If you can get a wire or probe in the the fan connector ground wire, measure the voltage to ground with the car running and A/C on. If you see any voltage, the ground connection is bad.
 

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Discussion Starter · #10 ·
OP, the correct schematic depends on whether you have Climatronic or not. If Climatronic, 58/7 is correct, and the fan control module wiring is virtually identical anyway.

This is puzzling, since you've replaced nearly everything. I presume you've verified with a meter the 40A and 5A fuses (on the 8-position relay panel) are still good?

If so, the next thing I'd check is the ground to the module. It's inside the car (circled 30, beside fuse panel), but worth looking at. A faulty ground would certainly keep all this from working. Be sure to measure resistance, rather than using the continuity mode. You should have way less than 1 ohm--virtually zero compared to your meter lead resistance (i.e. probes shorted together). The fan, in particular, pulls a lot of current.

If you can, check for voltage and ground at the control module connector. I don't know exactly how difficult it is to get at (never had to).

Since the 5A fuse is powered from the alternator (sorry Tom, just reading the schematic!), I tend to think the after-run coolant pump is powered from the 40A fuse, as well.
Fresco-
Just checked fuses. Good. Also, checked for 12v. That's also good. Maybe I didn't have a good ground last time I checked? So, I'm going to check ground like you recommended, then go to the fcm connectors.
 

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Which 5A fuse do you think has no power ?
Have you checked the coolant fan relay ?
Could you please answer these questions ?

There is a coolant fan relay, on your relay panel under the dash.

The only 12V supply from the alternator is terminal B+, (sorry fresco just reading the schematic with understanding from a long career in electrical and electronics)
The blue wire from the alternator (D+) does not connect to any fuse, and there is no 5A fuse in the fan control circuit.
 

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Discussion Starter · #15 ·
The most likely cause of your problem is a faulty coolant fan relay.
Tom-
I checked the 5 and 40 fuses. Both good. Also, there IS power at those fuses. My mistake. I must not be on the right diagram for my daughter's car because I don't see a fan control relay anywhere. What production number is stamped on it?
 

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Discussion Starter · #18 ·
OP, the correct schematic depends on whether you have Climatronic or not. If Climatronic, 58/7 is correct, and the fan control module wiring is virtually identical anyway.

This is puzzling, since you've replaced nearly everything. I presume you've verified with a meter the 40A and 5A fuses (on the 8-position relay panel) are still good?

If so, the next thing I'd check is the ground to the module. It's inside the car (circled 30, beside fuse panel), but worth looking at. A faulty ground would certainly keep all this from working. Be sure to measure resistance, rather than using the continuity mode. You should have way less than 1 ohm--virtually zero compared to your meter lead resistance (i.e. probes shorted together). The fan, in particular, pulls a lot of current.

If you can, check for voltage and ground at the control module connector. I don't know exactly how difficult it is to get at (never had to).

Since the 5A fuse is powered from the alternator (sorry Tom, just reading the schematic!), I tend to think the after-run coolant pump is powered from the 40A fuse, as well.
Checked ground 30 (I'm assuming that it's the one because it's next to fuses and has 1 large brown and 1 smaller brown). Both read .9 ohms.
 
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