Hot Time in The City

2006 Jetta AC continues to baffle me. Seems to work fine on 70-80 F days which lulls me into not doing anything. Then boom, into the 90s and the system takes a long time to wake up after hot soak. Example:
1. VCDS hooked up, engine at idle, blower on high.
2. After one minuet, no cooling fans spinning
VCDS readings:
1. CSV current .815 amps
2.Outside and cabin temps 87 F
3. System pressure 5.5 bar
4.Rad fan actual 10%
5. Rad fan Spec 0%

Increase in engine speed caused pressure to increase and fans started to operate.
New VCDS readings after a couple of mins of idling:
1. CSV current .815 amps
2. Outside and cabin temps 87 F
3. Compressor pressure 10 bar
4. Rad fan actual 35%
5. Rad fan spec 35%
6. Evap temp 68 F

Questions:
1. How are the fans controlled? Temp, pressure?
2. Is 5 bar normal at idle and no cooling fans on?
3. If the compressor control system valve is receiving max amps, shouldn't pressure be higher?
4. Shouldn't evap temp be closer to 0 deg C or 32 deg F

Through out the years I've had the system evacuated, vacuumed down, CSV replaced and the system recharged professionally.

Thanks for listening.

This is something for a Vw tech Specializing in AC


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2 options

1 - do without AC
2 - drive to nearest non-vw dealer and buy a different car

Can't do option #1. However #2 is very inviting. Recently bought a Model 3 for my wife and its damn hard to get into this car. Still hoping for an AC guy to jump in here.

How long ago since the RCV was replaced and system evacuated and recharged?

A few years ago on the RCV. Last year out of desperation I had it sucked down and recharged wit DuraCool. This system has never been cold and the DuraCool did improve the situation some. Another test tells me that the compressor has to make 9 bar before the fans come on. It took 3000 rpm to make this happen. Max pressure is about 10 bar. Thanks for your involvement.

If you’re not making pressure and the RCV is being commanded to allow the pressure then I’d say you either have:

A.) A bad RCV. I’ve seen RCV’s in new OEM compressors last as little as 3 years before they start acting up.

B.) A mechanically weak compressor.

C.) An undercharged system. It should hold 1.16lbs.

If you’re not making pressure and the RCV is being commanded to allow the pressure then I’d say you either have:
A.) A bad RCV. I’ve seen RCV’s in new OEM compressors last as little as 3 years before they start acting up. I've always been suspicious of this RCV and would gladly change it out again. I'd like to confirm the compressor is doing what it is supposed to.
B.) A mechanically weak compressor. How can I check for weak compressor, what kind of pressures should I be looking for?
C.) An undercharged system. It should hold 1.16lbs Considering I've had it done by friend with professional equipment I think we can eliminate this?

Another piece of data, Humming/moaning coming from evaporator or expansion valve.

I used a 7.5v power supply to supply 2a to my RCV as a temporary, emergency fix while I waited for the replacement RCV to come in. The additional current and voltage "made" the RCV work and I had cold AC for my trip.

You could try something like that to confirm proper compressor operation and a bad RCV.

You may just have a weak compressor. I keep RCVs on the shelf, once in a while when I suspect one is bad and I replace it, I have to end up replacing the compressor. Pretty rare, but it has happened.

Dorking around with cans of refrigerant will never get a proper charge level. For a true proper charge, the system needs to be evacuated, a vacuum put on, then recharged with a modern machine that can properly measure it. The margin for error is just too tight.

Couple other items on the BRM cars:

The cabin filter has a service interval of 20k miles. They are not kidding. These filters filter ALL the airflow, regardless of its source (inside or outside), so even if you run around with the A/C on recirc all the time, the filter in the A5 is still doing its job. If they get clogged up, air flow over the evap core will be weak, and you will have poor heat exchange.

The fans should run together, there is never a time when one fan should run without the other. They will come on low speed after the refrigerant pressure sensor hits a certain amount (I forget what), usually within 20-30 seconds of turning the air on. On a hot day, it will maybe even be faster... cool day, longer. If the pressure gets higher, the fan speed will increase. They generally won't ever turn back off once the initial pressure is high enough to turn them on.

Debris gets built up in the A5s, due in some part to the intercooler being a "full frontal" setup, so there is more places for junk to build up and hide. Starting at the front, it is: condenser--> intercooler--> radiator-->fan shroud/fans. The fans just pull air in, but if there is a bunch of debris between the three cores, then it will just pull air from the sides... not ACROSS the cores. Since the condenser is furthest away, it will suffer the most. On higher mileage cars (which by now most BRM cars are), may need to have the bumper cover removed and air blown in and around and through the cores to clean them out. You'd be amazed how much stuff is in there. And again, poor airflow means poor heat exchange. Which hinders the system's ability to remove heat from the cabin, which is what it is supposed to do.

Going back to the recirc mode: the little motor that works that door often dies. VERY common. I would venture to say by now more 2006 Jettas have bad ones that good. These fail often likely because Volkswagen thought it would be neat to put the system in recirc every time you put the car in reverse. Every. Time. So you may not actually be able to experience the full affect of the system if the recirc mode door is stuck. These motors are not all that expensive, and not all that hard to replace. The glove box has to come out.

Good thing my reverse sensor isn't attached

narongc73 said:

Good thing my reverse sensor isn't attached

Click to expand...

So, your reverse lights don’t come on when you’re in reverse?