AC Help - system won't charge

[5spdJunkie]

I have the ECON button won't go off problem. I replaced the pressure switch by the headlight. Fuses 1 and 6 are fine.

Using a rented vacuum pump and gauges. The system held vacuum for at least 30 minutes. Trying to fill from the low side it seems it will not take freon into the system.

The compressor will not come on to draw anything in. If I start the car and turn on climate control the econ light stays off for a few seconds. Then I can feel the compressor kick on for maybe 2 seconds. Then the econ light comes back on.

Any ideas?

[Kevin C]

Do you have a set of pressure gauges on the high side and the low side?

[5spdJunkie]

Do you have a set of pressure gauges on the high side and the low side?

Yes. The low side was up around 90. The high side wasnt getting about 55 or so.

[old guy]

That sounds like you have a clogged restrictor valve. Clicky click®

[5spdJunkie]

That sounds like you have a clogged restrictor valve. Clicky click®

awesome thanks. In your clicky what do you mean by clean the system? Can I replace the restrictor valve and vacuum the system again, then charge? Or is there something else?

[old guy]

I would start with just checking/ replacing the restrictor valve and going from there with a vacuum and recharge.

[5spdJunkie]

I would start with just checking/ replacing the restrictor valve and going from there with a vacuum and recharge.

Swapped it out. Vacuumed. Recharge. Same results. What's next?

[old guy]

Swapped it out. Vacuumed. Recharge. Same results. What's next?

What is your high/low static gauge readings? What happens when you then engage the compressor? Is the low side still reading higher than the high side?

[EuroxS4]

Swapped it out. Vacuumed. Recharge. Same results. What's next?

If the restrictor valve had alot of gray/metalish residue in it chance are it needs a compressor. However lets not assume anything yet. I would check compressor function first. Look at mvb 001 in 08 ac climate control head. It would show you current and duty cycle of compressor.Also scan for faults while your there. Normal operation of compressor should show around .6amps and a duty cycle of 64% showing a pressure of about 20bar in circuit. ECON light that wount turn off is normally because the system is empty and has less than 0.20kg of freon in it. IIRC thats the threshold for minimum operation.Normally on these cars charging is either done with a dedicated ac machine.Also the ac system needs to be put in a vacuum in order for it to draw or pull the freon into the system. You need to make sure you dont have any air in the supply hose coming from the refrigerant source your using to recharge the system.

[5spdJunkie]

What is your high/low static gauge readings? What happens when you then engage the compressor? Is the low side still reading higher than the high side?

I can't get the compressor to engage. The ECON light just stays on the whole time.

Low side about 90psi
High side about 75psi

I don't have a vag com so I can't scan for faults.

[EuroxS4]

They look almost even. It is possible you need a compressor but I cant rule that out without further checks.

[5spdJunkie]

You need to make sure you dont have any air in the supply hose coming from the refrigerant source your using to recharge the system.

I definitely didn't do this. I dont see how I could with my setup. I vacuumed the system. Let it sit for half an hour. Then I disconnected the vacuum pump hose and hooked that up to my refrigerant can.

[5spdJunkie]

They look almost even. It is possible you need a compressor but I cant rule that out without further checks.

I've ordered an OBDeleven tool and it'll be here tonight. Do you know how I need to scan using that tool?

[Kevin C]

To add to the conversation. The compressor has a variable displacement it goes from close to no pumping to full depending on a pwm signal from the control unit. To get it to charge you need enough initial pressure to set turn off the low pressure switches and a signal to the compressor. You can add charge if you have air in the system but the results will be poor. Air and moisture reduce efficiency and the moisture will cause acids to form and kill the system ( I know your vacuuming system, this is for others that might not know).

The sign of a pumping system is that the pump has a low enough pressure on the inlet side to draw from the can and you have a high pressure on the outlet. The scanner will help tell you if the pump is getting a signal or not. If it is and you have no pressure then the pump is suspect. As you get to the point where the system is taking a charge the cans of refrigerant will get cold and their pressure will drop. To keep things going you need to keep the cans in a pan of warm water.

As others have pointed out the first thing is to find out why the system is not pumping. A quick reality check it to compare the gauges with the car off, both valves open and the can valve shut. They should read the same pressure. Use that reading as a baseline to see what the pump is doing. It's not uncommon for the gauges themselves to be off by 5 to 10 psi. Use the off pressures to make sure your not just seeing a pressure based on the gauges not being accurate.

[john_gonzo]

5spdJunkie, have you verified the compressor is turning? The compressor pulley turns all the time. The center of the pulley should also be turning all the time. The center of the pulley is attached to the compressor shaft with a coupler. When the compressor goes bad (requires high torque), the coupler shears. When that happens, the center of the pulley no longer turns while the belt is driving the outer part of the pulley.

[5spdJunkie]

Got some codes

Trouble codes:
00710 - Defroster flap motor locked or has no voltage supply
Passive
00819 - High pressure sensor Signal too low
Passive
00819 - High pressure sensor Signal outside tolerance
Passive


Measuring AC block 001
(N280) 0 current
(N280) 0% duty cycle
High pressure signal(g65) - 95%
Refrisgerant circuit pressure 33 bar

[5spdJunkie]

Anything else to look at based on those codes?

[imnuts]

Your codes look like they're conflicting with the actual data. Can you clear them and see what comes back?

Sent from my Pixel 3 XL

[5spdJunkie]

I cleared the codes and 819 came back immediately. How are they in conflict?

[imnuts]

Signal too low code but it is showing 95% without the system running?

Sent from my Pixel 3 XL

[5spdJunkie]

What would cause N280 duty cycle to be 0% ?

[5spdJunkie]

Anyone? I don't understand what this duty cycle value means or what drives it

I'm about to do timing belt and I'm thinking about doing a compressor/drier while I'm in there.

[Turbo510]

Anyone? I don't understand what this duty cycle value means or what drives it

I'm about to do timing belt and I'm thinking about doing a compressor/drier while I'm in there.

(N280) 0 current
(N280) 0% duty cycle
High pressure signal(g65) - 95%
Refrisgerant circuit pressure 33 bar

Your pressure reads 33 Bar? That's like 480 PSI, which sounds awfully high to me. That's engine running? Maybe a blocked expansion orifice? I think that you need to go to AutoZone or wherever to borrow a gauge set, and confirm that pressure.

Is the N280 the control valve for the compressor? Duty cycle typically means time ON vs. Time OFF, so I would assume that 0% duty cycle means the control valve is not turning ON, therefore not allowing the compressor pistons to move in their cylinders. And that may be due to the high-pressure sensor signal being maxed out. You might try letting some refrigerant out to see if that sensor lets the compressor run.

[Nollywood]

Personally, I always leave air con recharging to the experts.

It’s a specialist job, which requires specific tools, and pre-charge procedures which may be outside the scope / capabilities of a basic charge-from-a-can setup.

[5ktq]

Your G65 sensor or the wiring to it is broken, (the one you replaced). ECU won't turn on AC if its getting crazy results.

You sure you plugged it in after you changed it? no damaged wiring?

[RENOxDECEPTION]

Just charged a b6 yesterday that was being problematic only accepting 5oz of refrigerant, and if you have the same pressure in both the high and low side (mine was charging to 80psi and no further), I had a spare high-pressure switch on hand, as soon as I swapped in the new one, the compressor started and high side started actually pressurizing, accepting more low side refrigerant (to a total of 17oz).

about the duty cycle, since the B6 uses a swashplate style compressor (as opposed to compressors with clutches), it controls the angle of the swashplate using a pwm solenoid rather than simple on/off operation of a clutch. the benefit is that it can infinitely vary the load the engine and a/c compressor are under for better efficiency.

Nice little gif for fun:


the solenoid would vary the angle of the plate and the center shaft.

[5spdJunkie]

Your G65 sensor or the wiring to it is broken, (the one you replaced). ECU won't turn on AC if its getting crazy results.

You sure you plugged it in after you changed it? no damaged wiring?

I'm sure I plugged it in but not sure the wiring isnt damaged. How would I check?

[Turbo510]

I just had a new Sankyo compressor and expansion orifice installed in my A4, which had been without AC for about a year. The swashplate variable-stroke arrangement shown above is key to the system working with only a simple orifice, to discharge liquid refrigerant into the evaporator as a cold gas. The pressure difference between the high and low sides is controlled by varying the compressor's displacement. It's nice to have cold air again!