AC acting up/bipolar

Hello,

Last year shortly after purchasing her, problems was barely noticeable.

Now.....

AC acted up at number 4 with musky air and while braking the cold air becomes warm with musky air and drive away and ac go cold. Has to be set at speed 6 and moving constantly.

Noticed the AC acted up during the raining season and it won’t run cold air almost none at all.

Sometimes When start the Passat, No cold air by driving 20-40 mph. It has to be high speed at least 50 mph to force the ac to run cold. I checked the fans, its both running. Which left me baffled.

Thinking its the RCV? Vw couldn’t find any issues with it for a year plus.

(Copied and pasted by my girlfriend)


Sent from my iPhone using Tapatalk

Make sure there is no air flow blockage, like a neglected cabin filter or a bunch of debris in the cowling under the trim at the base of the windshield. Make sure the case drain is not obstructed. Then watch the pressure with a scan tool and see if it changes when the load command goes up. The RCV is pretty common, too, and there is now a TSB for it so no excuse as to a dealer not being able to figure that out unless they cannot read at a 6th grade level.

Actually forgot to mention that I already replaced cabin filter twice since purchased, last year and few weeks ago, no difference. Definitely RCV or blockage somewhere. Will drop her off to my local trusty shop with 40 plus years experienced mechanics. Will check AC for free and will let me know from there.

Thanks oilhammer for the most valuable information.


Sent from my iPhone using Tapatalk

oilhammer said:

Make sure there is no air flow blockage, like a neglected cabin filter or a bunch of debris in the cowling under the trim at the base of the windshield. Make sure the case drain is not obstructed. Then watch the pressure with a scan tool and see if it changes when the load command goes up. The RCV is pretty common, too, and there is now a TSB for it so no excuse as to a dealer not being able to figure that out unless they cannot read at a 6th grade level.

Click to expand...

Dropped her off to my local trusty shop and the result is.....

The high and low pressure was way off. It was 155 high pressure and low pressure was 30. He evac the rest out and refilled new freon in and now at 200 high pressure and low pressure 35. Also replaced low side Schrader valve due to leaking. Now it blows icy cold!

Temperature gun clocked it at 37 degree at max fan speed, whoot! We shivered so hard like there was no tomorrow LOL

Thank you so much, oilhammer.


Sent from my iPhone using Tapatalk

Now the troubles are back.... blowing warm stubbornly. Tried to turn off AC for 2 minutes then back on, still blowing warm. Drove 15 mins then turned car off for dinner at a restaurant then back in the car, then blows cold. Argh!

Help???


Sent from my iPhone using Tapatalk

Guess I will order RCV, no I am not going to deal with idiots saying no not that not this etc. They dont listen.


Sent from my iPhone using Tapatalk

OK, just to clarify: it is IMPOSSIBLE for an A/C system to "blow warm". It just cannot do that. It can cool, or it can not cool. It cannot, in any capacity, RAISE the temperature. So, if it is in fact doing so, then you may have an issue with the temp blend door servo motor. If it is actually just not cooling (just passing whatever ambient temps outside are) then you may indeed have an RCV problem.

Yeah it felt hotter than outside. Outside was 88 degrees. Definitely RCV problem?


Sent from my iPhone using Tapatalk

A couple of things come to mind:

The last time was low charge. They *thought* it was the service Schraeder valve, but did they do a complete leak test? Might just be low again . . .

Could be RCV . . .

If still speed dependent, could be fans as well.

What has happened to me on some cars, is that when the charge gets low and outside temps rise, the compreasor can't build enough pressure to condense the refrigerant. Change any variable - IE cooling in the radiator due to ram air or fans coming on, or just cooler outside, it can then condense, and some cooling will come back. (This is typically the case when you slow to a stop, and cooling quits . . . lower compressor speed/output is a factor as well . . .).

When you stopped for dinner, it's likely the outside temp dropped . . . it could be as simple as that . . . (I had a Volvo 850 that told me it was low this way about every 3 years . . . too slow a loss to tear into it, so just topped it up, and went another 3 . . . the takeaway is simply that the symptom was the same as you see here . . . . RCV or none, low charge acts pretty much the same way . . .)

Myself, I'd go back to the last shop, and have them recheck charge . . . if it's OK, and all else checks out, then try the RCV, but not before you are certain that you didn't lose refrigerant.

Oilhammer has forgotten more than I will ever know about these cars but is it possibly a blocked drain line from the A/C? Long ago that happened to me with a Honda and when I hit the brakes at one point the water poured out of the unit onto my foot! Setting a higher fan speed might help with evaporation of the water?! Apologies in advance if this is ridiculous

Look up at my very first post in this thread. Notice the mention of a scan tool? The HVAC in that car is all electronic. It has OBD, bidirectional stuff, etc. The only way to properly diagnose this system is with a scan tool. You need to "see" the commanded compressor load, the refrigerant pressure values, as well as what all the servos in the dash are doing. We can sit and guess all day long. But until a scan tool is attached to the car, and some parameters are observed by someone who knows what they are looking at, the guesses are all we can have.

RCVs are very common. I also mentioned previously a TSB about it. I really cannot make it any simpler than that. I have also done the little servomotors. They typically will set a DTC. Some of them require taking the dash out. Little Chinese bits of low grade electronics buried in the NMS' dashboard, unfortunately.

I see.

I have VCDS, what group do I need to go into to see the compressor?


Sent from my iPhone using Tapatalk

Yep confirmed its the RCV and ordered. Wont arrive until Wednesday I got flaming mad at VW for wasting our time for a year. Complaint filed with VWoA.


Sent from my iPhone using Tapatalk