Hi team, after replacing my secondary rad fan (tested on 12v direct = good) I ran an output test, the fan didn't spin up?? Main fan did. What I'm wondering is if you run through the output test, if something didn't work would a fault against that component be logged??
I ran as can after the test and the previous fans error was not there (SDC code links to the fan). Fyi the old fan I took out did not spin up on 12v, and previous workshop testing ruled out the controller.
I haven't run the car to get the temp up and engage the AC as I've been flushing the coolant. I just wanted to check if output test failures triggered fault codes..
VCDS experts?
VCDS experts?
Last edited by Lander91 on Sun Sep 12, 2021 3:01 am, edited 1 time in total.
Re: VCDS experts?
If there was a detectable fault then it would be logged.
Did you make sure the AC was turned on (not on ECON mode or with a fault logged)? Did you make sure your engine was up to temperature?
Have you checked the fuse for that fan? Behind the drivers knee bolster.
Did you make sure the AC was turned on (not on ECON mode or with a fault logged)? Did you make sure your engine was up to temperature?
Have you checked the fuse for that fan? Behind the drivers knee bolster.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
Re: VCDS experts?
Also, log the temperature being sent to the HVAC, the ECU and the instrument cluster. I can never remember which one is used for the fans.
Log also measuring block 135 (ECU) when the AC should be running to see whats the duty cycle is.
If the duty cycle goes high and the fan doesn't run then check the output where the fan plug connector is (the octopus by the power steering reservoir, under the cover). This is better done with an oscilloscope if you have one. If not then a decent multimeter should show the voltage increase to 12v and back again when the output test is activated.
Log also measuring block 135 (ECU) when the AC should be running to see whats the duty cycle is.
If the duty cycle goes high and the fan doesn't run then check the output where the fan plug connector is (the octopus by the power steering reservoir, under the cover). This is better done with an oscilloscope if you have one. If not then a decent multimeter should show the voltage increase to 12v and back again when the output test is activated.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
Re: VCDS experts?
Oh, I should have read your post better. Yeah, fan won't start if the AC is off.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
Re: VCDS experts?
Hi,
When I'm doing output tests my engine is off, but key on, and aircon off. My experience is that each fan should start and stop according to the test so I don't know what's going on for you, except that you maybe had in fact 2 issues : the fan itself of course but also the wiring (including relays and fuses) and/or the controller.
So start checking the relays, fuses and wiring and let us know?
FWIW I had a secondary fan error at some point, and had a strange behaviour where the fan would spin when directly fed with 12 but wouldn't spin when activated with VCDS, like you. As my wires, relay and fuses were all OK, I got a second hand secondary fan controller but it didn't change anything. Later I bought a brand new fan (50€, not oem) from a vendor on ebay and it was all sorted.
When I'm doing output tests my engine is off, but key on, and aircon off. My experience is that each fan should start and stop according to the test so I don't know what's going on for you, except that you maybe had in fact 2 issues : the fan itself of course but also the wiring (including relays and fuses) and/or the controller.
So start checking the relays, fuses and wiring and let us know?
FWIW I had a secondary fan error at some point, and had a strange behaviour where the fan would spin when directly fed with 12 but wouldn't spin when activated with VCDS, like you. As my wires, relay and fuses were all OK, I got a second hand secondary fan controller but it didn't change anything. Later I bought a brand new fan (50€, not oem) from a vendor on ebay and it was all sorted.
RS6 C5 Avant 2003 Daytona Grey
Loba 650 turbos - Wagner IC - 200 cells cats - Milltek cat-back - Hotchkis bars - Bilstein B16 - MTM Wheels - oem coolant cap
Loba 650 turbos - Wagner IC - 200 cells cats - Milltek cat-back - Hotchkis bars - Bilstein B16 - MTM Wheels - oem coolant cap
Re: VCDS experts?
Thanks gents. I will run through your steps Shop, in case I end up in the same boat as you classik, can you give any details of the fan you managed to get? Audi tradition sell a NOS one but, it's like 300 euros..
Re: VCDS experts?
So on a whim I decided to have a closer look at the old fan. Aside from testing it to 12v and it not spinning up, it was also not putting out any appreciable voltage when spun with a drill. But I decided to take the old fan apart to have a nosey.
Hit a wall where the case is tabbed together, but with careful use of a cold chisel and hammer I managed to get the tabs out the way to seperate the case.
I'm no electrician but I fumbled around testing continuity etc and it seemed no issues there. Brushes seemed ok, but there was a LOT of carbon build up. A huge amount of contact cleaner later and I put it back together.
Spun up on 12v. Ran the output test with the fan sitting on the engine, as Shop days the 2 pin plug is located on the octopus. Spun up on Fan 2 output test.
I don't geddit.....
Rad support service position here I come... luckily I haven't refilled the coolant with the pink stuff yet.
Hit a wall where the case is tabbed together, but with careful use of a cold chisel and hammer I managed to get the tabs out the way to seperate the case.
I'm no electrician but I fumbled around testing continuity etc and it seemed no issues there. Brushes seemed ok, but there was a LOT of carbon build up. A huge amount of contact cleaner later and I put it back together.
Spun up on 12v. Ran the output test with the fan sitting on the engine, as Shop days the 2 pin plug is located on the octopus. Spun up on Fan 2 output test.
I don't geddit.....
Rad support service position here I come... luckily I haven't refilled the coolant with the pink stuff yet.
Last edited by Lander91 on Sun Sep 12, 2021 10:59 am, edited 1 time in total.
Re: VCDS experts?
That's odd. Perhaps the failing fan meant that the PWM wasn't enough to start the fan spinning. I'm not sure that the output test goes up to 100% duty cycle and it's possible that the current is limited coming out of the controller, whereas it wouldn't be if you're plugging it in directly.
Where did your replacement fan come from? Was it new? If you plug it in, start the output test and help the fan to start with your fingers, does it then spin?
Where did your replacement fan come from? Was it new? If you plug it in, start the output test and help the fan to start with your fingers, does it then spin?
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
Re: VCDS experts?
I think you might be right Shop. I didn't give the replacement fan, which is 2nd hand, a spin during the test. So like you say the current may not be enough to kick it. Based on what I've experienced with the cleaning of the original "failed" fan I think that the controller cant get it spinning with how they're run up. The output test for both fans seem to start at a very low speed and steadily ramp up to 100% then they're switched off after a few seconds.
Re: VCDS experts?
It might be worth checking the contacts and the earthing at the controller. If either is poor, that could limit the current getting to the fan which would exacerbate the problem.
You could get a generic PWM controller to test the fan to eliminate the controller. Eg:
https://www.amazon.co.uk/Controller-Adj ... B08QN39SJC
You could get a generic PWM controller to test the fan to eliminate the controller. Eg:
https://www.amazon.co.uk/Controller-Adj ... B08QN39SJC
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
Re: VCDS experts?
I think I will Shop, a controller like that is cheap enough. I know there'll be other uses, I'll try to find a lab power supply that has own output function.
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