blazej01

My AC is acting up. As you guys have suggested I scanned my car for codes and this is what I got. Nothing on HVAC. Could it be a bad fan?

dvs_dave

No, that’s not HVAC related. It’s for one of the coolant fans. Keep an eye on it’s function. Could be a random glitch, or it’s failing.

Either way, what is your AC not doing? Off the bat, most likely it just needs a regas.

blazej01

Do you know at what temp. Should the fan kick in. Right now with the AC on only passenger fan is working. Engine temp is normal.

As for the AC it works some times, then it stops blowing cold air then back on. No codes for HVIC.

PaulW

If only one coolant fan is running, I imagine your AC turns off when in stop and go traffic, at a stop light or when idling. If so, then it is tripping on high pressure due to not enough cooling in the condenser. Once you start moving, the pressure will reduce due to the air flow and the compressor will turn on.

If this describes your AC issues, troubleshoot / repair why the fan isn't running, and your problems will be solved.

blazej01

Just replaced cooling fan last night with a used one, but still I am getting the same code and the fan is not working. Do you guys have any ideal where I should look next. Thanks

Giovanni Giovino 6.0+6.0TT

Is there a way for you to swap fan connections to verify that the used fan you just purchased is a working unit ? I can not picture the connection in my head right now...

blazej01

So decided to pull my power probe and see if the fan is getting some kind of power. I am not sure how this fans work and which wire supposed to do what but maybe one of you guys knows better. This was done with AC on.

Here are my test results:

Brown wire- has ground
red/white wire- 14.3 was coming in
Red/yellow- has ground
purple wire - 13.9v was coming in

thanks

MP4.2+6.0

The heavy wires should be the actual power wires driving the fan, while the small wires will probably be the signal to switch. Beyond that, can't diagnose armchair. See Bentley manual wiring diagrams.

Your A/C description sounds to me like it is low on refrigerant. That would be the typical sometimes works, sometimes doesn't. From at least my W12, that didn't throw any codes, but when properly charged all cured. How that might relate to your fans I don't know.

My poor man's test for D3 and C5 4.2 fans was: 1. With engine cold at first start up (so no need for cooling fan), hit A/C to max--lowest temp setting and be sure A/C cools and that fan kicks on. Then, turn it completely off (Econ mode at least) so you know it won't engage fans in any way. 2. Then warm up car and wait for main fans to kick on. If cold outside, throw a tarp over grill area temporarily to force it to heat up. At expected temp gauge trigger point, expect main cooling fan to kick on. For my W12 that was slightly past the midpoint. 3. Now, almost regardless of temp, throw a tarp over grill area to force temp up further. Never go past ¾ though on gauge, and typically only around 5/8's. At that point the overdrive jet engine mode should kick in with major fan noise.

blazej01

Is there a way to check those fans manually ?

MP4.2+6.0

You can spin them up with VCDS if I remember correctly in a self test mode.

If all you have is an OBDII code reader, only good that will do is as a lightweight brick to hold down the tarp...

Not sure about applying power to them directly, especially w/ the four wires. The small wires suggest to me there are control electronics on board the fan unit.