B5.5 AC normal behavior?

So, finally got around to replacing the condenser on the car - AC was working, but not as much cooling as I would like - like 45 deg F out of the center vents on recirc , fan 2, for 10 minutes, 1500 RPM, no direct sunlight - I suspect the charge was a little low after 13 years.

Now.... replaced the condenser (bent from a long-ago racoon hit, and the lower fins were pretty much gone after 13 years of highway speeds, but not leaking), charged with 600g R134a, and the vent temps are good, but the compressor is cycling once the cabin is down to acceptable temps. For those interested, replacement is a Denso unit from RockAuto - fitment was OK - some slight bending of the inlet/outlet tubes was required, but otherwise fits fine. Didn't pop under the 250PSI high side pressures yesterday.

When the clutch kicks off, the vent temps rise... until the compressor kicks in again and the temps drop.

If I put the HVAC van on 3, the low side pressures stay a little higher and the cycling is reduced but not eliminated.

Electric fan works fine on high and low.

Looking at you Oilhammer - this is the only B5 I've had, no basis for comparison

Is it normal for this VDOT system to have the compressor cycle in normal operation?

Ambients are near 90 deg F up here this week - I expect that the cycling will get worse once the more normal 80-85 deg weather comes back.

What's the low side pressure when the compressor cycles off? Is the outlet of the accumulator, and the suction line at the compressor cold?

-J

Funny you mention this, as I have had a similar issue with one of my B5s that has me somewhat stumped, but I admit I have not done a whole lot to address it.

My BHW B5's A/C works fine, always has.

My AWM B5's A/C in comparison sucks. And it is beyond the fact that it is a black wagon vs. the gray sedan of the BHW car.

What my AWM does, is the A/C compressor comes on after the usual ~10 second delay after start up. Not sure why VAG does that, but the compressor relay is called a "retardation relay" and it does work that way. But it is somewhat slow to cool, and if you come to a stop in the first 10 minutes or so of driving, the compressor will kick off (like waiting for a stop light), then kick back on again once you take off. After about 30 minutes of driving, it no longer does that. And by then the interior is reasonably comfortable. Whereas the BHW car is comfortable in 10 minutes, and after 30 minutes it will give you an ice cream headache.

The B5s still use an orifice tube system, a holdover from the old Audis. I would view this as a less efficient means of A/C, but once it is going it normally cools the car down just fine. A $90k Phaeton or A8L uses the same type setup, so it must be OK. But I still think the expansion valve systems in VAG cars get colder quicker, at least that has always been my experience.

Anyway, when I got my AWM, the compressor was a little noisy, and it was not making much of a pressure change. So I immediately put a new Denso compressor on it, and it was better, but still not as good as I thought it should be. Then I took the orifice tube out, did not see any appreciable debris, just some minor gray tinge, but I put a new one in anyway (cheap, easy), and it is still about the same. When it finally gets to behaving, after that ~30 minute period, it will cool the car down. And the fan will happily be buzzing along at high speed (also works on low... these step the speed down with an old-fashioned series resistor, again a holdover from the 1980s). Clutch fan seems to work fine, engine temp is maintained at normal operating range no matter the ambient temps or driving conditions.

I am thinking there may be a case where the pressure sensor (out front, behind the bumper cover near the passenger side headlamp) gets flaky and does not work correctly and I *think* is causing a high side cutout situation. But it is difficult to nail down when exactly it happens because I obviously cannot drive down the road with gauges attached.

Since I rarely drive the car on short trips, and except for recently (because my Golf is getting some body work done) I rarely drive the car at all, I have not made it much of a priority. But I really need to get to the bottom of it as it sounds a lot like what you are dealing with.

I just charged mine today but I haven't tested it much. You're welcome to come by and compare if it's of value to you.

On a totally non-related note I hear the new 1234 gas is a real PITA. Guys tell me it takes like 2hrs worth of BS to re-charge them with all the tests the system has to go through to introduce the gas

Brian's96TDIPASSAT said:

On a totally non-related note I hear the new 1234 gas is a real PITA. Guys tell me it takes like 2hrs worth of BS to re-charge them with all the tests the system has to go through to introduce the gas

Click to expand...

Boy you are not kidding. That machine is an hour long ordeal to go through. Fortunately it is mostly automated, but still you have a spot in the shop tied up for that whole time. Ridiculous.

While we are saving the planet with newer refrigerants, scientists have been struggling to find out why R11 levels have stopped declining, even though it was banned 8 years ago. It turns out that it is being widely used in China for blowing foam insulation in the home construction industry.

https://www.bbc.com/news/science-environment-44738952