Air Conditioning Questions (again)

You can probably label me a lurker, since I very rarely post. That’s because I really don’t have anything of value to add that everyone else already covers.

I’m know this topic has been covered many times before, but for all the searching I do on this site, I’m still confused about what to do next.

Car info:
01 Jetta TDI
170,000 miles
Purchased at 155,000 miles in Jan of this year
Bone stock

Because I only bought this car in January, I don’t know how long ago the AC might have actually worked properly. A couple weeks ago, on a 90 deg day, I noticed that the AC wasn’t doing much (if any) good. So, I purchased a DIY, add a can kit to add some 134. IIRC, the system had ~25 PSI. I bumped it up to ~35, and it “appeared” to do some good. However, the next day, I was back to worse than I was before. I’ve been reading ever since. In the mean time, I purchased a set of gauges. It appears that the compressor is working. The clutch appears to engage (hard to see from above), and when I press the “AC” button, the rpm’s very quickly drop. My best guess as of today, was that I had over-filled the system. So, I got out all my gauges and started to hopelessly work on it tonight. The Temps were taken with a Craftsman digital multi-meter with a temp probe (not the IR kind).

After driving the car home from work (1.25 hour drive) with the AC on high the entire way. Here are my numbers, please let me know what you think:

Ambient outside air temp 86 deg

Low pressure reading: 30
High pressure reading: 100
Vent air temp: 86 deg

Low pressure reading: 30
High pressure reading: 90
Vent air temp: 94 deg (notice, it’s higher than the outside air temp)

Low pressure reading: 30
High pressure reading: 80
Vent air temp: 95 deg (notice, it’s higher than the outside air temp)

Low pressure reading: 30
High pressure reading: 60
Vent air temp: 95 deg (notice, it’s higher than the outside air temp)

FWIW - I was bleading the Low-pressure side. The Low pressure would drop, then raise, then level back out at 30. Now I’m stumped. What should I be looking at next? I was thinking the dryer/filter and/or the expansion valve.

Any help would be greatly appreciated.

AC possibilities

You are reporting both low side and high side pressures that are low. The two possibilities are that your expansion valve is stuck open or the RCV (refrigerant control valve) in the compressor is stuck.

I suppose that you could take the system down, and replace the expansion valve first. Then recharge the system. If it works, you have your fix.

However, I suspect the RCV is stuck. I am unaware of a separate repair part for this. Maybe you could find a like compressor that is bad for a leak and get one out it this. However, for my money, I would replace the compressor, expansion valve, and receiver dryer. Then I would recharge properly.

This would ensure a fix. I wish I could get you closer, but, I had an RCV valve stick suddenly on my B3 VR6 passat and it acted the same way. I new compressor, and dryer, and now my wife has cold air.

Thank you for the good reply dzl.

I had already ordered the dryer & expansion valve (hadn't come in yet). I'll call and order a compressor also.

Ohh the fun that must be to replace that thing.

Can anyone tell me how many volts are supposed to be supplied to the compressor for the clutch to operate? I'm only getting 9.5 volts. I suspect that that's not enough to engage the clutch.

Please help... my vacation starts today and we need the car

nevermind... forgot to hook the pressure sensor connector back up.

clutch is engaged now. Thanks anyway

I do have 1 more question... How much pressure should be on both sides? I understand not more than 30-35 on the low side. How about the upper side?