Peculiar HVAC issue - no air but blower works?!

There were no error codes given (no VCDS presumably), so we had to work out what was at fault.

RAB
 
Hi guys!

g263 reads almost the same as fresh air temperature but I actually have a spare sensor so I can switch to see if that solves the problem. Haven't had too much time since last post though. Will do it when I have some time. Running econ mode in the meantime and not having any problems.

Completed the HVAC label file. I had to add .txt to be able to upload it here. Remove .txt and put it in VCDS\LABELS\USER folder and try it if you want. I haven't sent it to Rosstech yet. Feedback is much appreciated so it may be corrected before sending it in.

cheers!
 

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Hi guys!

g263 reads almost the same as fresh air temperature but I actually have a spare sensor so I can switch to see if that solves the problem. Haven't had too much time since last post though. Will do it when I have some time. Running econ mode in the meantime and not having any problems.

Completed the HVAC label file. I had to add .txt to be able to upload it here. Remove .txt and put it in VCDS\LABELS\USER folder and try it if you want. I haven't sent it to Rosstech yet. Feedback is much appreciated so it may be corrected before sending it in.

cheers!
It seems that you have VCDS but you haven't posted the results of any scan. That might help!

RAB
 
I posted the intermittent error on n280 short to plus i have had once but it hasn’t occured since. The measuring blocks gives plausible values without any abberations.
 
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Ross Tech instructions are to ignore A/C intermittent fault codes. I have never scanned my car without same but the A/C functions normally.

RAB
 
Ok so here is the deal

Today fuse 38 went. Power steering and oil level sensor warnings in cluster.
Replacing fuse only led to one more broken fuse :D
VCDS found multiple errors (due to the broken fuse)
Disconnected G56 and N280 because suspicions... replaced fuse, success.
Connected G56, still fuse holds up.
VCDS only reports the disconnected N280

Ergo, N280 AC regulator valve is faulty. This must have been the issue from the beginning, with the evaporator freezing up and blocking air flow. Changing valve is easy and I have a replacement but... I guess the refrigerant needs to be emptied and pressure relieved which demands special equipment :(

Todays question: Is it ok to drive with the N280 disconnected? Will that result in minimum or maximum ac level?

greetings

.s
 
Safe to drive? Yes, I believe it is, because, as long as minimum refrigerant flow through compressor is maintained, the compressor is happy. Don't know the N280 state when disconnect. My guess is minimum. You'll soon find out (if evap freezes)!
Mac.
 
Thanks Mac! So you think the disconnected valve would still allow some refrigerant flow?
I think so, yes. I think the (N280) is designed to never completely close (< 2%), to prevent compressor damage under any failure conditions.
Depending on the way your N280 has failed (probably the coil has shorted, hence fuse blowing), it may be stuck anywhere between 2 & 100%, but most likely is 2%.
Regards Mac.
 
Took a test drive with measuring blocks this evening. N280 disconnected. Pressure stable at 3.6-4.0 bar so there is certainly some output from the compressor although the valve is disconnected. This means that the disconnected valve effectively results in minimum AC setting. The PWM duty cycle actually shows 0% but this is the controller output, not a measured value. Since this is the cold season the AC would have been off anyway so I have plenty of time to fix this now :D (although I guess some misting could occur). Maybe if I push the ECON button the HVAC brain will use a program that is optimized without AC?

Thanks for the help guys! Merry Christmas
 
Update! Long story...

I finally got around to replacing my N280 valve. When preparing for the procedure I nocited that the visible end of my valve didn’t look the same as the replacement valve I ripped from the breakers.

The valve on my car has a very small connector on the valve itself. This was completely corroded and filled with metal oxides. Add water and this would explain the short circuit. After a little bit of research my conclusion is that the ac compressor on my car probably has been replaced with an aftermarket unit with a valve from Denso. They seem to put a pigtail cable from the valve itself to the connector on the car. Probably to make it easier to use the same valve on different brands of cars. Unfortunately this is a very small connector with special terminals. I could not find any replacement terminals to crimp on.

Thus I decided to get rid of the connector completely. First I checked that the valve was ok. I measured the coil resistance to 10.3 ohms which seems plausible. The valve actuates with an audible click when fed with 12V and draws 1.2 A. I proceeded with cutting the valve connector body open, exposing the pins. After cleaning these with a file I was able to solder new cables to the valve. After shrink tubing with glue I embedded everything in a blob of fiber reinforced epoxy.

Reconnected the valve. Everything works great. How this would relate to my initial problem of diminished HVAC air throughput I have no idea whatsoever.

Greetings

.s
 
Reconnected the valve. Everything works great. How this would relate to my initial problem of diminished HVAC air throughput I have no idea whatsoever.

From cold, with ECON on (no A/C) and AUTO selected, the fan will run very slowly at first because there is no heat to distribute. As the engine/coolant warms up, the fan speed increases. It's the same with A/C. With a defective N280, the A/C cannot cool adequately, so the fan runs slowly.

RAB
 
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