Aircon fault + what pressure should be in the system?

[jokh]

Hi All

So 1 year with no A/C and now i am trying to get it to work.

So far i have changed then compressor, orfin filter, dry filter, high pressure pipes, pressure sensor, all o-rings and the radiator.
When putting the new system together, i put PAG 46 oil (180ml) directly in the compressor and system.

Today i went to the mechanic, got him to vaccum the system, and after that fill in new r134 fluid.

But the econ mode is still stuck on - vcds shows me the fault code:

00819 - High Pressure Sensor (G65)
16-10 - Signal Outside Specifications - Intermittent

Because i changed the sensor yesterday, i dont think that it is the problem. I tried to "hot" wire the signal to the compressor and then the A/C works and i get cold air.

I did the VCDS 001 measuring blocks and found that:

With aircon OFF, or Econ mode On (NO Cold Air):
High-Pressure Signal (G65) ---> 24%
Refrigerant Circuit Pressure ---> 6 Bar


With aircon ON (Hot wired, Cold Air):
High-Pressure Signal (G65) ---> 99,5%
Refrigerant Circuit Pressure ----> 33 Bar


My question is the following:
1) when i already have put the PAG46 oil into the system before vaccum, does vaccum
2) What should the pressure in the system be, right now it shows 6bar OFF and 33 bar ON? Can it be true thatthe pressure in the system is to high --> so i have to much fluid in?
3) If not the above what could else could be wrong, for my A/C not to work? Other things i can measure with VCDS, that would help me?


Thank you very much

[old guy]

I suspect that you may have overcharged the system. What was the low side reading when the high side was 33 bar?



Some good reference info in this thread: Clicky click®

[jokh]

Thank you.
I suspect the same. I dont have access to any thing to measure the low side with, i only have VCDS at the moment. But i will try to let out some R-134a tomorrow and see if i can get the pressure down, maybe it will work:)
Do any of you know anything about the oil in the system? if it stays inside during vacum or i have to refill?

[old guy]

The oil should stay in when you pull vacuum on the system.

[Kevin C]

The best way to get the charge right is to put a known amount into an empty system. How much did he put in? All the other methods are a bit of a guess, but better than nothing. 33 bar is 487 PSI!!!! Either you need a new sensor or a new mechanic or your system has some other issue. You need real highside / low side and temp readings. Also, is your condenser cooling fan working?

[jokh]

The car got 500grams, which should be perfect. Today i removed 30 gram to see if that would bring the pressure down. Now the pressure in the system with the pump Off is 5 bars, which is good.
When driving, the car sometimes turns the aircon On and it cools perfectly for 1 minute max, then it goes into Econ mode again.

The mechanics all say that something else is wrong with the system, and that it is what causing such a high pressure? however i dont think of any other reason, since all is changed. Can it be that i had the dryfilter open for 20 minutes?

The only measuring tools i have right now is VCDS, can i do anything with that, that can help me find the cause?

Can it be the HVAC control module inside the car that is not working? or could it be a bad wire?

Again only fault code i have is the 00918.

[jokh]

also next week i am driving home from vacation in the car and need the A/C, would you dare just to "hot" wire a button in and then just activate it "manually"? or would that cause any major harm? Basically that would just be to ignore the fault message

[jokh]

Also i went to a mechanic today to see what his aircon measuring clock would read,when activating the aircon his measure clock went way above 300 psi, then we shut it off. The low side was not high maybe about 20 psi

[old guy]

also next week i am driving home from vacation in the car and need the A/C, would you dare just to "hot" wire a button in and then just activate it "manually"? or would that cause any major harm? Basically that would just be to ignore the fault message

If it is still in an overpressure condition you will probably destroy the compressor.

[jokh]

Hmm what i thought:)
So tomorrow i will have to go to a mechanic and get the readings. wo i would want to measure the follwoing:
1. high and low side pressure with engine+ compressor Off
2. high and low side pressure with engine running and compressor Off
3. high and low side pressure with engine + compressor On

And if high side are still high, the only reason would be in there is some resistance in the system, which would cause bad flow, or what would you think?

[old guy]

Correct. Something restricting flow such as the dryer or the restrictor valve.

[jokh]

I went to the shop today, and they cannot measure the pressure before tomorrow, so i will wait.
However he mentioned that my aircon cannot work if my fan does not run. He then says that the heat build up will then cause the over pressure.
When i measured the 33 bar, i was driving highway, which got me believing that my condenser would get plenty or air to cool. So is it true, that "high way" air is not enough, that it also need fan on full blast? Also when i measure with VCDS, it goes from 6 bar static and as soon as i activate aircon it goes to 33bar, so im having a hard time believing that the pressure goes from 6 to 33 bar in 5 sec only caused by not enough cooling (i was driving highway, so it would have gotten some cooling).

Another thing i thought of is that right now i measure the high pressure when i "manuelly" activating the aircon, so im applying 12V to the signal wire on the restrictor valve on the compressor. Is this restrictor valve only a On-Off valve, or does it normally regulate the restriction? My point is, that im applying 12V which will make shut down close to max on the valve, if the valve normally only get "5V" then i would, by giving 12V cause the restriction flow?

[jokh]

Sorry for writing a lot.

I did some more testing, when loging with VCDS. I can see that when the engine is Off, i measure 6bar pressure in the system --> however then i was looking around for a while and suddendly the pressure jumped to 33bar again, this happened with engine still Off. Now i can see that with engine Off it keeps jumping between 6 and 33 bar, no in between only these two values.
Then when engine is On and aircon Off it just stayes at 33 bar. But i can see that some times values with aircon On drops to 12 bar and then its working as it should for some secounds.

Could i have gotten a defect pressure sensor? or can i have mounted it wrongly? maybe i did tighten it to much?

[DJMurphy]

Isn't there a mesh screen somewhere in the system that can get plugged with debris, spiking pressures? Can't find the thread about it atm.

[jokh]

Isn't there a mesh screen somewhere in the system that can get plugged with debris, spiking pressures? Can't find the thread about it atm.

are you talking about the orfin filter?:)
But i think i have tracked the problem down to an electric issue.

[jokh]

Correct. Something restricting flow such as the dryer or the restrictor valve.

I think i have a lot more info now that can help find the problem:
The pressure in the system are fine, and behaves as is should.

However the problem i find is as following:

With Engine and AC On i can measure 3,5 Voltage from the G65 Signal wire, i can track this all the way into the HVAC controller, so the controller gets the signal perfectly.
When the HVAC recieves this signal from the G65 (3,5V) it sends out 8,5 Voltage into the N280 restriction valve. Now the system is cooling.

Then i hook up my VCDS and read HVAC measuring block 001. Everything seems fine. But as soon as i hit the gas pedal a little the measuring blocks in VCDS jumps directly to 33 bar and the HVAC controller cuts off the 8,5 Voltage to the N280 valve. While the VCDS readings jumped to 33 bar, i was measuring the voltage going from G65 to the HVAC controller, to see if it changed. It stayed the same.

So my readings tell me that my G65 sensor is working as it should, and is very steady. However the VCDS tells me that the value jumps from correct, directly to 33 bar and ECON mode.

My question is:
Where do i get the VCDS readings from? is it the HVAC controller that sends the measurements to the VCDS? If so i would assume that my HVAC controller is broken? Because the Voltage going into it, i measure them to being correct and steady, meanwhile my VCDS tells me that the HVAD controller is jumping around from correct to massive overpressure, and a cut in power.

[old guy]

When I was referring to a clogged restrictor valve (aka orifice tube) this is what I was referring to: Clicky click®

[Kevin C]

Pressure readings with a gauge set would be a great way to verify. Also, the compressor gets a PWM signal that varies its displacement. I have no clue what happens when you give it a full 12 volts and max it out, it just might over pressure. My understanding is that the restriction is not regulated, it seems logical that the pressures are controlled by the variable displacement pump (the control point is probably the temp of the evaporator).

http://www.cancore.net/wp-content/up...ompressors.pdf

[Kevin C]

https://forums.ross-tech.com/showthr...he-HVAC-Season