1 is ground. What do you mean 12v?

 

I meant 12V across the two, since 1 is ground. In any case it's working. (though I guess that's obvious if the fan is running @ max LOL)

 

Nice...

 

Did you check what I suggested in #44?

 

No, not yet. Unfortunately I had to wrap it all up for today. Will get back on that soon enough

 

Seeing the amount of corrosion in that box, you may need to take it out to ensure that wires aren't rotten/shorting under it.

 

Got a bit of a doozie of a problem.

This started out intermittent..Sometimes from a cold start the fan would immediately go to 100% speed. And oh boy let me tell you, that fan is LOUD. And it seems hard on the car. I actually raised my idle in VCDS to help somewhat in the middle of troubleshooting this because 850 watts is no joke, you can tell its a heavy load.

When you would shut off the car the fan of course normally stays on just for a couple of minutes... which is normal. But in this scenario, it still does run at full speed with the car off. So after this happened a couple of times, I would actually disconnect the fan after shutting the car off. Just to preserve some battery + the lower voltage in this situation prob isn't good.. I'd hate for something to burn up.

I had checked VCDS a few times and kept seeing electrical malfunction on the fan control circuit on the engine module. What I did not know is -- me disconnecting the fan would generate this code. After my testing today I realized it would not generate this code until I unplugged the fan, which in hindsight makes sense.

Knowing this is an uncommon issue -- I got myself a junkyard fan assembly. Kept it on hand waiting for this problem to re-appear.

This problem ended up stopping, and actually went away for a couple of months. This week though it came back and it's done it every time I've started the car. So my commute to work has been: go out to car, start it, open hood, connect fan (which then goes full speed). Get to work, open hood, disconnect fan, then turn off car. This is getting pretty old quickly, so tonight I replaced the fan assembly. Not too hard -- other than the bolts to the left (driver's side) intercooler pipe. But got through it. 2 hours later I go for a drive just to make sure everything is working annnnnd fan is running full speed

So I guess where do I go from here? Car is outside of warranty I believe (134k miles), although the dieselgate stuff was done on it in 2019. But I'm pretty sure this wouldn't even fall under emissions at all. I don't know if I trust the VW dealership here either. This is a problem that will probably take a diagnostics deep dive as I don't think just having a scan tool is going to help, since the car literally thinks nothing is wrong.

I have limited knowledge of CAN bus networks, but my current assumption is that the radiator fan perhaps lost connection to the engine control module? So it's just running at 100% speed to be "safe" because it can't read anything from the ECM. I just think it's weird that this scenario doesn't generate a code. Anyone knows if it's supposed to?

Attached are some screenshots from when I dug a bit more closely into VCDS tonight. I'm open to ideas if anyone has any!

No codes after plugging in fan (which is confirmed to be running full speed) and clearing codes, going for a 10 min drive:
View attachment 255364

Me confirming the car has the correct coding for the cooling fan. Which it seems to. It's the single fan that's regulated. (Not so regulated in my case LOL)
View attachment 255365

Couple of measuring blocks just to see..I think the ECM thinks the fan is running @ 10% speed? Which I promise you is not true. (need to add an extra 0 there, buddy!)
Also lol @ the difference in temp between radiator outlet and engine outlet. The thermostat may have closed though when I was on this screen. Might be why.
View attachment 255366


And finally I went to the Output tests.. I saw there was one for the fan control circuit. And there was the action of "off". I performed this action and NOTHING HAPPENED. So either A. this test is broken. or B. I may have confirmed my idea that the engine module cannot talk to the fan?
View attachment 255368

I have the same issue with my 2012 3.0 Hybrid with 178k. I haven't dived myself into is as much as you but I too have no codes fr what I can see with my OBDELEVEN app. My mechanic took it for a couple days and hooked his computer to it and didn't find anything either. So he went back to check the coolant system and found that the water pump has a vacuum switch that is NOT working so it is running at 100% at startup. He says that there is vacuum all the way to tube on the pump so the solenoid inside the pump must not be working. Not sure if the TDI has the same type of water pump but that might be something to look at as well if you haven't already. As we Treg owners have learne EVERYTHING is connected in these things and they are to "smart" for thier own good sometimes... Waiting on my water pump to come in to change it and will let you know if anything changes...

 

So if there's no continuity between the connector and controller, it could never react to the pwm signal that it doesn't receive.

I'm assuming that what you showed on the scope was off the connector? If so, click the a/c on and watch the signal change. Or run output tests with VCDS and watch it change.

 

Or use the duty setting on the multimeter to see what the ECU is telling the controller as far as PWM signal.... You should see it increase when you put the A/C on or run output test. You may have to backprobe the wires as I don't know if it will do output test if it senses your controller isn't hooked up.

 

It’s 100% the wiring between the fuse box and the fan unit itself. Likely the connection on the underside of the white connector

I spent almost the entire day trying to figure out how to get the bottom side of that connector out of the fuse box. There’s no fuse box disassembly instructions in the FSM.

i 100% figured this out by taking some bulk 18awg wire, pulling the pin out of the fan header of the pigtail that I got with the junkyard fan, and pinning it into my car’s fan connector and connecting it to the ecu via the top Side of the connector in the fuse box.
It worked perfectly. Normal fan was back.

the thread may end here as I’ll prob end up doing a hack job because im sure getting VW to replace the entire box and wiring just because I can’t get on connector out will be thousands.

but for those who want to know the ECU seems to output a pretty steady 3.5V to the fan controller. It’s not much of a curve or anything so I couldn’t make sense of it, but this is what it looks like on a $30 scope (that tbh I don’t entirely know how to use)

 

I spent almost the entire day trying to figure out how to get the bottom side of that connector out of the fuse box. There’s no fuse box disassembly instructions in the FSM.

Huh? Like you can't take the Sbox out to get to the bottom of it where all the wiring comes into it?

 

Spray down the whole fuse box in Deoxit and let it dry off. That stuff is magic

Nice detective work in any case!

 

I'm currently debugging the same issue, P0480 error code in VCDS, fan runs at 100% all time. I've tried two new fans units and the issue is still there.

Just want to confirm here, pin#4 of the female end of fan connector should have continuity to pin#3 of the 17-pin male end in the fuse box?

And the female end of the 17-pin connector goes to the the ECU?

 

Fixed the issue the ghetto way😂😂

I spliced a wire from pin#4 of fan connector to pin#3 on the 17-pin connector. Normal fan was back! Now I need to weather proof and do some cable management....

 

Not surprising you have electrical issues looking at the state of that connector.