forum.audiv8.com Foren English Audi V8 Forum Aircon- compressor clutch not being activated

During the process of running the diagnostics to check out a few other problems (my other recent threads), the diagnostics for the instruments are supposed to trigger the relay that controls the clutch for the compressor.

Questions.
Where is the relay located? It's not listed on the main relay panel?

One man show here

Do you have any fault codes? If the auxiliary fan does not work seriously the ECU will disengage the aircon automatically.

The diagnostic output tests suggest that the relay that controls the compressor will switch-

[quote]
-Remove the jumper wire after about 4 seconds, and the LED test light will then begin to blink out the 3433 and the radiator fan will step through the 3 speeds of its operation.
Now insert the jumper wire again for about 4 seconds and remove, then the code 3434 will be blinked out, and the A/C compressor relay will click on and off.
Insert the jumper wire again for about 4 seconds and remove, then the code 3443 will be blinked out, and the fuel gauge should show approximately 15 gal, the coolant temperature gauge should show approximately 80C (176F), and the interior lights are switched on.
Insert the jumper wire again for 4 seconds and remove, then the code 3444 will be blinked out, and the warning buzzer in the instrument cluster will sound.
Insert the jumper wire again for 4 seconds and remove, then the fault code 0000 will be displayed (LED will flash on/off at 2.5 second intervals to signify the 0000 code) The fault code memory will now be erased.
[/quote].

Now. It may be that the diagnostics don't all function due to difference between LHD and RHD models.
The radiator electric fan is now functioning, after some wiring repairs. But the radiator fan is only controlled when the AC is on. The diag tests would likely be independent.

However. After some digging, the aircon system pressure is down, anyway. There is no pressure at the schrader valves

In Antwort auf:

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However. After some digging, the aircon system pressure is down, anyway. There is no pressure at the schrader valves

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That's your problem. You need to evacuate and refill the system. The aircon will also be shut down, if the pressure is too low. And you need to delete all recorded fault codes.

Well, maybe/possibly. But the diagnostics produce the blink-code, but there is no sound of a relay being switched, and there is no statement about the system being up to pressure. It's a diagnostic function, rather than a system function.
Rather like activating the various controls in the transmission

Hi,
don´t forget, the compressor clutch function depends on the low pressure switch; means, when there`s not enough pressure on refrigerant, the clutch doesn´t work...

Yes, in operation. But is it the same under diagnostics?

I think so.
The signal from control unit is going to the A/C-relay, which switches the clutch.
If the low-pressure-switch is turned off, because of loss of refrigerant, their´s no voltage on the contact of the relay.
Relay is mounted on 1st auxilliary relay trap at place 10.

No 10, under the floor boards? (No British political jokes, please)

Yes.

Political Correctness. Indeed.

I checked the relay plate.

Pin 31 is ground. No problem there.

Pin 30 is the signal from the low pressure switch. Currently, 0v, due no system pressure.
I've bridged the switch to give a hi signal, 30v. This is also connected to the Ac control head.
Pin 87 is the output to the compressor clutch.
Pin 87a is going to the Motronic(kick down?) (idle control?)
Pin T is getting nothing

Hello,
everthing correct.
Pin 87a is for idle control, pin T is from the thermostate for frost control.
The other cable of pin 30 is the low-pressure-signal for A/C-control.
Does the clutch work?

The clutch doesn't switch if I short the pins, but it doesn't matter. The relay is not being energised, anyway.

The clutch doesn't switch if I short the pins, but it doesn't matter. The relay is not being energised, anyway.

______________________________
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VAS 5054A ODIS

Jackie- Sounds like you have the same problem as I have.

No! Wait. Sounds like you have a different problem. You are repeating my words. That's a whole other problem which I think cannot be fixed on a car forum. My niece, age 6, used to do that. Are you age 6?

*ROFL*

At the risk of inviting unsolicited comments from deluded idiots peddling crap, I'm resurrecting this thread as an update.

Update part 1.
R24 gas is available locally, and I'm going to use this to recharge one of my 3 V8s
The compressor clutch initially wouldn't engage, and it appears that both high and low pressure switches are not working correctly. By temporarily shorting them out, the compressor runs. Yeehaa.
So next is to get a full charge of gas in there.

Maybe I should replace the associated valves sitting behind the switches?

Update part 2
My niece is actually much older, and rarely listens to me, let alone repeats what I say.

I got some life from the system. The low pressure switch is not working. With a positive charge in the system, the lo-press switch remains open..
Short the switch, the clutch operates.

...and then the pump bearing goes.
So I pull the pump out, and try to get to the front bearing. With the shaft nut removed, the clutch should pull free. But it doesn't. What's the secret?

just replying to bump this up, in the hope that someone might know how to get the zircon pump pulley assembly apart.
i now have two pumps, one with a good pump and knackered clutch. The other has a good clutch, and damage to the pulley.