Fans don't work with AC on

[kareems]

Hello

as the title says, turning the AC on doesn't turn the fans on

I started by making sure that the compressor works, the pressure sensor works, the fans work on both low and high speeds when the car heats up, the AC has normal air not R134a which is supposed to be suffcient to trigger the pressure sensor and the fuses on the battery are working

I suspected it's the fans relay and tried multiple relays with the letter "K" similar to the one in the car but it didn't work

what am I missing? Could the problem be that the circuit contains normal air not R134a?

[petrolcan]

I suspect you are missing R134a hence no cooling.

[kareems]

31 minutes ago, petrolcan said:

I suspect you are missing R134a hence no cooling.

as far as I understand if I press the AC button and turn the fan speed on it should turn on both fans immediately but that’s not what happens, pressing the AC button doesn’t turn on the fans they remain off

am I wrong about that? Is it normal for the fans to remain off?

[Breezy_Pete]

What pressure are you seeing reported by sensor G65?

I suspect that with only air in the system the pressure will not reach the necessary threshold to trigger fan operation.

[kareems]

3 hours ago, Breezy_Pete said:

What pressure are you seeing reported by sensor G65?

I suspect that with only air in the system the pressure will not reach the necessary threshold to trigger fan operation.

I am not exactly sure since I checked the pressure at a repair center but if I recall right I think the gauge measured 150-200 PSI

how much PSI should it be for the fans to operate?

[Paws4Thot]

6 hours ago, kareems said:

Hello

as the title says, turning the AC on doesn't turn the fans on

I started by making sure that the compressor works, the pressure sensor works, the fans work on both low and high speeds when the car heats up, the AC has normal air not R134a which is supposed to be suffcient to trigger the pressure sensor and the fuses on the battery are working

I suspected it's the fans relay and tried multiple relays with the letter "K" similar to the one in the car but it didn't work

what am I missing? Could the problem be that the circuit contains normal air not R134a?

As I'm reading this, like everyone else I'm thinking that your a/c has leaked some or all of the working fluid so will never operate.

[Breezy_Pete]

On models I'm more familiar with, I think 9 bar/130psi for low speed, from memory.

Have you checked cabin fuse 10? No.16?

What is your engine code please? there are differences in wiring diagrams for different engines.

Edited 8 June, 2023 by Breezy_Pete
fuse number correction

[kareems]

Just now, Paws4Thot said:

As I'm reading this, like everyone else I'm thinking that your a/c has leaked some or all of the working fluid so will never operate.

By working fluid you mean the R134a?

That is true it currently doesn’t have R134a in the pipes but my issue is not that the AC doesn’t cool

The issue is that the fans don’t start when I try to turn the AC on, aren’t they supposed to start whether the pipes have R134a or ordinary air? Since both would trigger the pressure sensor

1 minute ago, Breezy_Pete said:

On models I'm more familiar with, I think 9 bar/130psi for low speed, from memory.

Have you checked cabin fuse 10?

What is your engine code please? there are differences in wiring diagrams for different engines.

Last time I checked all the fuses were working but I would check them one more time today to make sure

my engine code is 75kW AVU according to the sticker in the boot 

[Breezy_Pete]

Cabin fuse No.16 (10 Amps)  seems relevant for your engine code. I think where I wrote No.10 in previous post was an error, will correct now.

[Paws4Thot]

44 minutes ago, kareems said:

By working fluid you mean the R134a?

That is true it currently doesn’t have R134a in the pipes but my issue is not that the AC doesn’t cool

The issue is that the fans don’t start when I try to turn the AC on

Yes. The LP fan doesn't start because you don't have a refrigerant under pressure in the air conditioning pipework. Anyone who is telling you otherwise is more interested in getting the contents of your wallet than in repairing your car.

[Breezy_Pete]

What's an LP fan?

The OP has two radiator fans, both twin speed, wired in parallel according to the circuits. 

[kareems]

37 minutes ago, Paws4Thot said:

Yes. The LP fan doesn't start because you don't have a refrigerant under pressure in the air conditioning pipework. Anyone who is telling you otherwise is more interested in getting the contents of your wallet than in repairing your car.

One repair guy mentioned that but what's the logic behind it? that doesn't seem right to me, would be glad if you explained it to me

from what I understand whether the pipework contains refrigerant (R134a) or normal air the most important part is that it's enough to trigger the pressure sensor to run the fans once the AC button is pushed

and regarding the fans, as Breezy_Pete said:

34 minutes ago, Breezy_Pete said:

What's an LP fan?

The OP has two radiator fans, both twin speed, wired in parallel according to the circuits. 

by LP fan I think he means Low Power fan? since the fans have 2 speeds?
and yes I have 2 radiator fans with twin speeds wired in parallel as far as I know as they both turn on/off together

 

52 minutes ago, Breezy_Pete said:

Cabin fuse No.16 (10 Amps)  seems relevant for your engine code. I think where I wrote No.10 in previous post was an error, will correct now.

I will make sure to check that fuse among the other fuses today, last time I checked all were fine but yesterday the radiator (30A) fuse above the battery went dead out of the blue so I will check both fuse boxes according to the attached diagrams to make sure they are working and have the right amps and report back but as far as I know the fuses weren't the problem

 

[J.R.]

I will give you a couple of nuggets to reflect on and then maybe the penny will drop with you.

 

The fans will only cut in when the AC pump raises the pressure of the liquid refrigerant above the threshold, they should not cut in as soon as you press the AC switch, the pump has to compress the liquid and bring it up to the threshold pressure.

 

Liquids are incompressible. Air is compressible 💡

 

R134a is pumped in the liquid state and expands to the gas state in the evaporator creating cooling, I've kept that bit simple it is only to illustrate that a refrigerant gas goes between the two states.

 

If your name was Ian and not Kareems I would think you were the muppet that I tried in vain to explain why it was stupid to pump up the hydrolastic suspension on his girlfriends Mini with a garage airline, I tried but failed, hopefully you will be more receptive.

 

You have now contaminated your system with moisture from the compressed air, the filter drier will need replacing and the system dried with several long vacuum downs.

 

Had you in fact resolved the issue which caused you to be working on and ultimately screw up the AC system?

[Warrior193]

27 minutes ago, J.R. said:

I will give you a couple of nuggets to reflect on and then maybe the penny will drop with you.

 

The fans will only cut in when the AC pump raises the pressure of the liquid refrigerant above the threshold, they should not cut in as soon as you press the AC switch, the pump has to compress the liquid and bring it up to the threshold pressure.

 

Liquids are incompressible. Air is compressible 💡

 

R134a is pumped in the liquid state and expands to the gas state in the evaporator creating cooling, I've kept that bit simple it is only to illustrate that a refrigerant gas goes between the two states.

 

If your name was Ian and not Kareems I would think you were the muppet that I tried in vain to explain why it was stupid to pump up the hydrolastic suspension on his girlfriends Mini with a garage airline, I tried but failed, hopefully you will be more receptive.

 

You have now contaminated your system with moisture from the compressed air, the filter drier will need replacing and the system dried with several long vacuum downs.

 

Had you in fact resolved the issue which caused you to be working on and ultimately screw up the AC system?

I wonder, is OP mistaking 'normal air' in his AC for OFN being put in the system for a pressure-drop test?

Edited 8 June, 2023 by Warrior193
typo

[kareems]

 

40 minutes ago, J.R. said:

I will give you a couple of nuggets to reflect on and then maybe the penny will drop with you.

 

The fans will only cut in when the AC pump raises the pressure of the liquid refrigerant above the threshold, they should not cut in as soon as you press the AC switch, the pump has to compress the liquid and bring it up to the threshold pressure.

 

Liquids are incompressible. Air is compressible 💡

 

R134a is pumped in the liquid state and expands to the gas state in the evaporator creating cooling, I've kept that bit simple it is only to illustrate that a refrigerant gas goes between the two states.

 

If your name was Ian and not Kareems I would think you were the muppet that I tried in vain to explain why it was stupid to pump up the hydrolastic suspension on his girlfriends Mini with a garage airline, I tried but failed, hopefully you will be more receptive.

 

You have now contaminated your system with moisture from the compressed air, the filter drier will need replacing and the system dried with several long vacuum downs.

 

Had you in fact resolved the issue which caused you to be working on and ultimately screw up the AC system?

First of all, excuse me since I am not an expert in cars yet as I have been into fixing that Skoda for a couple of months only and I hear lots of bull**** from different people and it takes loads of effort to understand the right thing to do specially that I am not familiar with the car-related English terms

Second, my issue isn't resolved nope, the timeline went as following;

I had an issue with the AC and went for and electrician repair shop to check the car, I found out that the fans work only in high speed and had some engine/coolant thermostats + big fan replaced fixing the fans making them work in both high and low speeds. I decided to check the AC pipes if they needed to be filled with R134a since it wasn't cooling and the AC repair guy started checking and told me that the following parts are working fine; the pressure sensor, the compressor, and the engine went louder a bit when I pressed the AC button, but he said the fans should kick in and they didn't and thought that the fan relay needs to be replaced so I tried different relays but nothing changed which made me come here and ask to find out if I am misunderstanding or missing something

Third, what you are trying to say here is that I need to vacuum my AC pipelines and add R134a first for the fans to kick in when I press the AC button and that it's completely normal for the fans not to work when the pipes aren't vacuumed and filled with liquid refrigerent, did I get that right?

14 minutes ago, Warrior193 said:

I wonder, is OP is mistaking 'normal air' in his AC for OFN being put in the system for a pressure-drop test?

I am not sure I am familiar with the terms OFN and pressure-drop test

what I am sure of is that the AC repair guy used this gauge to measure the pressure in the AC pipes and the arrow on the blue one was between 150-200PSI if I recall that right since there are mutliple measurments

Edited 8 June, 2023 by kareems

[Warrior193]

OFN is Oxygen-free Nitrogen, which is used to pressure-test the AC system - but the AC should never be run with this gas in the system , as the compressor will not have sufficient lubrication. 

Edited 8 June, 2023 by Warrior193
repetition

[Breezy_Pete]

This diagram is close to what  you have @kareems, but not exactly right, as the wiring diagram suggest you have a G65 pressure sensor instead of the F129 pressure switch, and in that case it is  mounted after the condenser, rather than before in the refrigerant circuit. Pressure is pressure though.

 

There's a 'lost in translation' between the LP/HP key at the top and the marking in the diagram, which is ND (niedrig druck)/HD (hoch druck) instead. Low and high pressure respectively.

 

Gas to liquid transition happens in the condenser as I understand it.

 

 

From document D3E801B9571-Air_conditioning_system_with_refrigerant_R134a

 

 

 

[J.R.]

12 hours ago, kareems said:

the AC has normal air not R134a which is supposed to be suffcient to trigger the pressure sensor

 

Maybe there has been a misunderstanding Kareem, can you explain what you meant by the above comment please?

 

Nothing you have subsequently said (which should have been explained at the outset) suggests that the aircon guy has removed the refrigerant or that the system has leaked its refrigerant, why do you say it contains pressurised air and not R134a?

 

If the guy used the manifold set and the system was filled with sufficient refrigerant then he would have first seen a low side pressure on both guages, say 125psi but it depends on temperature, then when the aircon cut in the low side should drop and the high side go up as the compressor works, again the values depend on temperature but also in this case humidity, from memory the high side needs to go above 200psi for the fans to cut in.

[Yop]

Sorry to cut in on OP's post , but my car is in the  local garage   today  with my    aircon  being looked at .  All I know about  AC is  what Ive just read above in this thread, so not  a naturally technically minded  person.     Hes supposed to be coming back to me before repairing as Ive no idea of costs.  .  What sort of costs am I looking at for a couple of the most common scenarios of what could be wrong with it please  if thats not an impossible question.   When I switch on the  ordinary blower  on hot and cold seems ok , but  nothing further kicks in when I press the AC  . 

[J.R.]

Most common will be low refrigerant pressure and the cost will be that of a recharge, I'm 20 years out of date with UK prices but from what I read between £65 and £140.

 

Most other jobs will entail that cost in addition to the work done, the exception being the high side pressure sensor which can be replaced without evacuating the system, a 10 minute job and a cheap part but still ends up being charged out at a fortune.

[Yop]

Ah,  thank you  JR  .  Gives me some idea anyway   . My car appeared to be first in the Q   and its four hours in now and Ive heard nothing yet,  so  my  purse is starting to tremble lol!  Fingers crossed its something  simple and not too expensive .   Nearly melted in it the other week , so I dread to think what it must be like in France if ones AC goes.  I remember from holidays  the murder of getting into the car after a  shopping trip  till you get going and the AC kicks in . and of course its even hotter over there these days with global warming .