No air conditioning, help.

[Shortrun]

I have measured the static pressure and it is 70 psi, both high and low side.
Outside temperature is 72 F.

I am trying to figure out if the compressor clutch is coming on. See the link, this is what my compressor looks like.

https://www.europaparts.com/ac-compr...05s-denso.html

I am not familuar with this compressor, other ones i have seen the wire goes in near the pulley.
The centre part of the pulley is turning all the time. Even if i pull out the Air Con 10 amp fuse.

Any ideas, please.

[Boost92]

Did You mesure the pressure with the car on and AC on?

[diagnosticator]

The compressor on our A4s does not use a drive clutch. The compressor is driven by the engine whenever the engine is running. The compressor is a variable displacement type, and the HVAC controller controls the variable compressor output of refrigerant based on the heat load on the A/C system.
The drive pulley on the compressor has a break-away device in the pulley hub, to allow the accessory drive belt to continue rotation if the compressor seizes up. If the hub release is activated, the cause for the drive pulley hub release must be determined if possible, and a new pulley must be installed on the compressor.

[Shortrun]

Did You mesure the pressure with the car on and AC on?

Yes, the pressure does not change. Car running or not.

[Shortrun]

The compressor on our A4s does not use a drive clutch. The compressor is driven by the engine whenever the engine is running. The compressor is a variable displacement type, and the HVAC controller controls the variable compressor output of refrigerant based on the heat load on the A/C system.
The drive pulley on the compressor has a break-away device in the pulley hub, to allow the accessory drive belt to continue rotation if the compressor seizes up. If the hub release is activated, a new pulley must be installed on the compressor.

Ok, so it could be the compressor or the controller?
There are 2 wires going into the compressor, can i check there for voltage an learn something usefull?

[diagnosticator]

Ok, so it could be the compressor or the controller?
There are 2 wires going into the compressor, can i check there for voltage an learn something usefull?

The wires connected to the compressor, send a control signal from the HVAC controller to a valve in the compressor that is used to vary the pumping displacement of the compressor. You can measure the value of the control signal applied to the compressor, it is a variable frequency square wave voltage and is always present when the A/C is in Auto or manual mode, but is off at zero volts in Econ mode. The average time based voltage aka the Duty Cycle of the signal is the variable of interest, besides the presence or absence of a signal value greater than zero according to the operating mode selected.

[JKCutler3]

Here is what it sounds like when your compressor goes bad. Was $1,400 at the dealer.

[Shortrun]

So i certainlly should have said this in the beginning.
The Econ light will not go off.

I have edited my first post to include the outside temperature is 72 F. ( i know this is important)

I have an oscilloscope and can check the duty cycle.

That compressor does sound awfull. Mine has no sound all.

[rocket1420]

Yes, the pressure does not change. Car running or not.

Do you have the AC on full blast? What gauges do you have? When you hook them up with the car running and the A/C on, the pressures won't stay the same. If they do, then either something is clogged, like the orifice tube (or whatever Audi calls it), or the compressor is bad.

EDIT: Also, 70 is waaaaay too low for the high side. That could indicate a leak somewhere. But if your pressures never change, and they are both 70 when it's 72 degrees out (humidity is also important), then refrigerant isn't moving.

[diagnosticator]

So i certainlly should have said this in the beginning.
The Econ light will not go off.

I have edited my first post to include the outside temperature is 72 F. ( i know this is important)

I have an oscilloscope and can check the duty cycle.

That compressor does sound awfull. Mine has no sound all.

If the ECON light won't turn off, usually means the system pressure is to low, preventing the compressor from activating. In this case the system needs to be recharged.

Did you mean to say the compressor does not sound awful?

The actual Duty Cycle of the compressor control signal is irrelevant if the compressor is not activated and pumping refrigerant.

I recommend having the A/C system serviced by an Automotive A/C repair shop. There are several wrong ways to recharge the system, but only one correct way to do it.

[Shortrun]

If the ECON light won't turn off, usually means the system pressure is to low, preventing the compressor from activating. In this case the system needs to be recharged.

Did you mean to say the compressor does not sound awful?

way to do it.

Thanks, right, the compressor makes no sound at all. Which makes sense, with the Econ light ON the compressor would not be asked to turn on..

I will look into refrigerant level. Thanks again.

[imnuts]

Can you scan the HVAC module for faults? Your compressor isn't engaging with the ECON light coming on. There should be a code (or codes) stored stating why.

[Shortrun]

Do you have the AC on full blast? What gauges do you have? When you hook them up with the car running and the A/C on, the pressures won't stay the same. If they do, then either something is clogged, like the orifice tube (or whatever Audi calls it), or the compressor is bad.

EDIT: Also, 70 is waaaaay too low for the high side. That could indicate a leak somewhere. But if your pressures never change, and they are both 70 when it's 72 degrees out (humidity is also important), then refrigerant isn't moving.

The only control i have is to set the cabin temperature to LOW
Thanks, my compressor is not running so all i can measure is static pressure.

[Shortrun]

Can you scan the HVAC module for faults? Your compressor isn't engaging with the ECON light coming on. There should be a code (or codes) stored stating why.

I wish i could scan.
I have the ebay little blue thing to interface between the car port and the computer. But the very old laptop will not run the software i downloaded.

[rocket1420]

If the ECON light won't turn off, usually means the system pressure is to low, preventing the compressor from activating. In this case the system needs to be recharged.

Did you mean to say the compressor does not sound awful?

The actual Duty Cycle of the compressor control signal is irrelevant if the compressor is not activated and pumping refrigerant.

I recommend having the A/C system serviced by an Automotive A/C repair shop. There are several wrong ways to recharge the system, but only one correct way to do it.

If the system pressure is low, that indicates a leak, and it needs to be found instead of just putting in more refrigerant (not saying that you were advocating that, just trying to make the point). I'm also posting under the assumption that the a/c worked at one point (like last summer), which I guess the OP never actually stated. One of the best ways I've found to find a leak is to use an a/c UV leak detection kit. You put a little UV dye into the system, then use a blacklight and glasses to find where the dye is coming out.

You might also push on the schrader valve on the low side with a screwdriver to see if there's any charge in the system at all. Just push on it briefly, and wear safety glasses. You don't want refrigerant in your eyes.

Of course, if all of this is over your head or you don't want to invest in the tools to do it right, then just do as diagnosticator said and take it to a shop.

[Shortrun]

Good point about the ac working, it was good last year in Sept. But is too cold here in the winter. It is just now that many of us in Ontario are turning on our AC for the first time in 6 months.

I do have manifold gauges, which is how i know the static pressure. Also have a vaccum pump but have not used it on this repair job yet.

[diagnosticator]

Good point about the ac working, it was good last year in Sept. But is too cold here in the winter. It is just now that many of us in Ontario are turning on our AC for the first time in 6 months.

I do have manifold gauges, which is how i know the static pressure. Also have a vaccum pump but have not used it on this repair job yet.

Using Auto and manual mode, in the winter the A/C is still active and the cooled dehumidified air is reheated in the heater section of the HVAC air handling unit. Using dehumidified air from the A/C prevents fogging of the windows, and increases the defrost/defog function effectiveness. The A/C is turned OFF in ECON mode.

[rocket1420]

If the ECON light won't turn off, usually means the system pressure is to low, preventing the compressor from activating. In this case the system needs to be recharged.

Did you mean to say the compressor does not sound awful?

The actual Duty Cycle of the compressor control signal is irrelevant if the compressor is not activated and pumping refrigerant.

I recommend having the A/C system serviced by an Automotive A/C repair shop. There are several wrong ways to recharge the system, but only one correct way to do it.

Isn't 70 psi way too high for 72 degrees? The charts I've read say it should be 35-40 psi. Or is that irrelevant if the refrigerant isn't moving, as in this case?

[diagnosticator]

Isn't 70 psi way too high for 72 degrees? The charts I've read say it should be 35-40 psi. Or is that irrelevant if the refrigerant isn't moving, as in this case?

Correct, the low side pressure is the same as the high side pressure if the compressor is not pumping refrigerant. The only aspect that the system static pressure represents is the state of charge in the system. The system charge can still be low with 70 psig static pressure at 72 degrees. If the compressor was allowed to operate, the low side pressure would be a lot lower than the static pressure.

If the A/C is locked out in ECON mode, typically means the system pressure is to low.

[Boost92]

Get someone that knows what they do to take the refrigriant out Then pressure test with nitrogen ( to find the leak, if it is one )If there is one fix it! Pressure test once more. ( to see if it holds) then vackum the system to get air etc out of the system since it has been open. Now refill refrigriant :)

[Shortrun]

Problem has been resolved.

Again the static pressure was allways good. There were no leaks.
Replaced the high pressure sensor today. The Economy light now will go off. The cold air is blowing.

Our outside temperature is only about 60F here today so i did not bother putting gauges on. I will wait till it is a little warmer an check the operating pressures.

Thanks for all the input.